,transcriber's ,notes ,text printed in italics has been transcribed between underscores1 bold face text between tildes4 ,small capitals have been replaced with ,,all ,,capitals4 text and text represent subscript and superscript texts respectively4 ,more ,transcriber's ,notes may be found at the end of this text4 ,,the ,,rare ,,earths ,,the ,,rare ,,earths ,,their ,,occurrence1 ,,chemistry1 ,,and ,,technology ,,by ,s4 ,i4 ,,levy ,b4,a4 7,,cantab471 ,b4,,sc4 7,,lond471 ,a4,i4,c4 ,,late ,,hutchinson ,,research ,,student ,,of ,,st4 ,,john',s ,,college ,,cambridge ,,with ,,illustrations ,,london ,,edward ,,arnold #aiae ,all rights reserved ,,preface ,during the thirty years which have elapsed since ,dr4 ,auer's application of the rare earths to the production of artificial light1 the incandescent mantle industry has developed to an extent which gives it a prominent place among those chemical industries which may be considered essential to modern civilisation4 ,this technical development has in turn assisted and stimulated the scientific examination of the elements of this group1 with the result that ordered and accurate knowledge is beginning to replace the confused and uncertain data which had been collected by earlier workers in the field4 ,these advances have served to emphasise the scientific interest and importance of the rare earth group1 and the difficulty of bringing it into relation with the other elements4 ,the relatively scant attention devoted to the study of this province of inorganic chemistry by teachers and students in ,england is probably due no less to the difficulty in classification1 and the uncertainty with regard to the homogeneity and individuality of the various members of the family--an uncertainty by no means entirely removed even now--than to the fact that the very extensive literature on the subject is somewhat confused and difficult of access1 especially to those unfamiliar with the ,french and ,german languages4 ,the present work is intended to give a general but fairly comprehensive account of the rare earth group4 ,in accordance with general usage1 the elements zirconium and thorium have been included1 though these are now recognised as falling outside the limits of the rare earth group proper4 ,the inclusion of titanium1 which chemically is so far removed from the cerium and yttrium elements1 has been considered desirable1 not only on account of its general occurrence in the rare earth minerals1 and its position in ,group ,,ivb with zirconium1 cerium1 and thorium1 but also on account of its increasing chemical and technical interest1 and its use in the ordinary quantitative laboratory operations4 ,though the nature of the matter embraced has rendered the division into three parts desirable1 the whole subject has been treated primarily from the chemical standpoint4 ,in view1 however1 of the occurrence of considerable quantities of monazite within the ,british ,empire1 and of the possibility that in the near future the ,brazilian fields will not remain the sole source of thorium nitrate1 stress has been laid on the technical aspect1 which is more especially developed as regards the production of monazite and the incandescent mantle industry in ,chapters ,,vii and ,,xvii-,,xx4 ,in the preparation of ,part ,i full use has been made of ,dana's indispensable #8,system of ,mineralogy1' as well as of the encyclopdic #8,handbuch' of ,hintze1 whilst for ,part ,,ii the excellent monograph of ,r4 ,j4 ,meyer1 in ,abegg's #8,handbuch1' ,vol4 ,,iii1 ,div4 ,i1 and the work of the same author and ,hauser1 #8,die ,analyse der seltenen ,erden und der ,erdsuren1' ,vols4 ,,xiv-,,xv of #8,die ,chemische ,analyse1' have been of service4 ,i have great pleasure in expressing my gratitude to ,mr4 ,a4 ,hutchinson1 of ,pembroke ,college1 ,cambridge1 who has kindly read for me the manuscript of ,part ,i1 and suggested improvements2 to ,dr4 ,h4 ,j4 ,h4 ,fenton1 of ,christ's ,college1 who has given me similar assistance in ,part ,,ii2 and to ,dr4 ,s4 ,ruhemann1 of ,gonville and ,caius ,college1 who has read ,parts ,,ii and ,,iii4 ,i am also greatly indebted to ,mr4 ,e4 ,j4 ,holmyard1 of ,sidney ,sussex ,college1 who helped me with the preparation of ,part ,,ii2 and to ,mr4 ,h4 ,m4 ,spiers1 of ,gonville and ,caius ,college1 who read the proofs for me with special thoroughness and care4 ,i have also to thank ,professor ,soddy and his publishers1 ,messrs4 ,longmans1 ,green ,co41 for kind permission to reproduce from #8,the ,chemistry of the ,radio-,elements' the diagram on p4 #ach4 ,s4 ,i4 ,,levy4 ,,contents ,,part ,i ,,occurrence ,,of ,,the ,,rare ,,earths ,,chapter ,,page ,i4 ,,the ,,nature ,,of ,,the ,,minerals ,,and ,,their ,,mode ,,of ,,occurrence #a ,,ii4 ,,the ,,silicates #cj 7a7 ,silicates of ,yttrium and ,cerium ,metals--,cerite2 ,gadolinite1 ,glowing of ,minerals2 ,allanite1 ,hellandite1 ,thalnite and ,thortveitite2 etc4 7b7 ,silicates of ,thorium and ,zirconium--,thorite1 ,zircon1 ,naegite2 etc4 7c7 ,mixed ,silicates--,eudialyte1 ,beckelite2 etc4 ,,iii4 ,,the ,,titano-,,silicates ,,and ,,titanates #eb 7a7 ,titano-silicates--,yttrotitanite1 ,titanite2 etc4 7b7 ,titanates--,yttrocrasite1 ,delorenzite1 ,ilmenite2 etc4 ,,iv4 ,,the ,,tantalo-,,columbates #fj 7a7 ,containing no ,titanium ,dioxide--,samarskite 7,annerdite71 ,plumboniobite1 ,yttrotantalite1 ,fergusonite1 ,sipylite2 etc4 7b7 ,containing ,titanium ,dioxide--schynite2 the isodimorphous series ,euxenite1 ,polycrase1 ,blomstrandine1 ,priorite2 ,risrite1 ,wiikite2 etc4 ,v4 ,,the ,,oxides ,,and ,,carbonates #gb 7a7 ,oxides--,uraninite1 ,thorianite1 ,baddeleyite2 ,rutile1 ,anatase and ,brookite2 etc4 7b7 ,carbonates--,lanthanite2 ,parisite 7,synchisite71 ,cordylite2 etc4 ,,vi4 ,,the ,,phosphates ,,and ,,halides #hb 7a7 ,phosphates--,monazite1 ,xenotime 7,hussakite72 etc4 7b7 ,halides--,yttrocerite1 ,yttrofluorite2 etc4 ,,vii4 ,,the ,,monazite ,,sands #ij ,,viii4 ,,radioactivity ,,of ,,the ,,minerals #ii ,,part ,,ii ,,the ,,chemistry ,,of ,,the ,,elements ,,ix4 ,,general ,,properties ,,of ,,the ,,cerium ,,and ,,yttrium ,,groups #aaa ,x4 ,,general ,,methods ,,of ,,separation #adb ,,xi4 ,,the ,,cerium ,,group--,,cerium #aef ,,xii4 ,,the ,,cerium ,,group 7,,continued7--,,lanthanum1 ,,praseodymium1 ,,neodymium1 ,,and ,,samarium #afh ,,xiii4 ,,the ,,terbium ,,group #ahd ,,xiv4 ,,the ,,erbium ,,and ,,ytterbium ,,groups--,,yttrium ,,and ,,scandium #aid ,,xv4 ,,the ,,group ,,iva ,,elements--,,titanium #bai ,,xvi4 ,,the ,,group ,,iva ,,elements 7,,continued7--,,zirconium ,,and ,,thorium #bch ,,part ,,iii ,,the ,,technology ,,of ,,the ,,elements ,,xvii4 ,,the ,,incandescent ,,mantle ,,industry--,,historical ,,and ,,general ,,introduction #bfe ,,xviii4 ,,the ,,chemical ,,treatment ,,of ,,monazite #bge ,,xix4 ,,the ,,manufacture ,,of ,,mantles ,,from ,,cotton ,,and ,,ramie #bia ,,xx4 ,,artificial ,,silk--,,its ,,production ,,and ,,use ,,in ,,the ,,mantle ,,industry #cja ,,xxi4 ,,other ,,technological ,,uses ,,of ,,the ,,cerium ,,and ,,yttrium ,,elements1 ,,zirconium ,,and ,,thorium #cac ,,xxii4 ,,the ,,industrial ,,applications ,,of ,,titanium ,,and ,,its ,,compounds #cbe ,,index #cdb ,,table ,,of ,,abbreviations ,,employed ,,in ,,the ,,references ,abstr4 ,chem4 ,soc4 ,abstracts in ,journal of the ,chemical ,society4 ,amer4 ,chem4 ,j4 ,american ,chemical ,journal4 ,amer4 ,j4 ,sci4 ,american ,journal of ,science4 ,annalen ,justus ,liebig's ,annalen der ,chemie4 ,ann4 ,chim4 ,phys4 ,annales de ,chimie et de ,physique4 ,astrophys4 ,j4 ,astrophysical ,journal4 ,ber4 ,berichte der ,deutschen chemischen ,gesellschaft4 ,berz4 ,jahres4 ,berzelius' ,jahresbericht ber die ,fortschritte der ,chemie und ,mineralogie4 ,bull4 ,imp4 ,inst4 ,bulletin of the ,imperial ,institute4 ,bull4 ,soc4 chim4 ,bulletin de la ,socit chimique de ,france4 ,bull4 ,soc4 franc4 ,min4 ,bulletin de la ,socit franaise de ,minralogie4 ,bull4 ,soc4 franc4 ,photog4 ,bulletin de la ,socit franaise de ,photographie4 ,bull4 ,u4 ,s4 ,geol4 ,survey ,bulletin of the ,united ,states ,geological ,survey4 ,cass4 ,mag4 ,cassier's ,magazine4 ,centr4 ,min4 ,centralblatt fr ,mineralogie1 ,geologie und ,palontologie4 ,chem4 ,eng4 ,chemical ,engineer4 ,chem4 ,ind4 ,chemische ,industrie4 ,chem4 ,news ,chemical ,news4 ,chem4 ,zeitg4 ,chemiker ,zeitung4 ,chem4 ,zentr4 ,chemisches ,zentralblatt4 ,compt4 rend4 ,comptes rendus hebdomadaires des ,sances de l',acadmie des ,sciences4 ,dingl4 ,polyt4 ,j4 ,dingler's ,polytechnisches ,journal4 ,d4 ,r4 ,p4 ,deutsche ,reichspatentschrift4 ,e4 ,english ,patent ,specification4 ,elect4 chem4 ,ind4 ,electrochemical ,industry 7since #aijd1 ,electrochemical and ,metallurgical ,industry74 ,f4 ,brevet d',invention de la ,rpublique ,franaise4 ,j4 ,amer4 ,chem4 ,soc4 ,journal of the ,american ,chemical ,society4 ,j4 ,gasbel4 ,journal fr ,gasbeleuchtung4 ,j4 ,gaslighting ,journal of ,gaslighting4 ,j4 ,ind4 ,eng4 ,chem4 ,journal of ,industrial and ,engineering ,chemistry4 ,j4 pr4 ,chem4 ,journal fr practische ,chemie4 ,j4 ,russ4 ,phys4 ,chem4 ,soc4 ,journal of the ,physical and ,chemical ,society of ,russia4 ,j4 ,soc4 ,chem4 ,ind4 ,journal of the ,society of ,chemical ,industry4 ,met4 ,chem4 ,eng4 ,metallurgical and ,chemical ,engineering4 ,min4 ,mag4 ,mineralogical ,magazine and ,journal of the ,mineralogical ,society4 ,monats4 ,monatshefte fr ,chemie und verwandte ,theile anderer ,wissenschaften4 ,phil4 ,mag4 ,philosophical ,magazine4 ,phil4 ,trans4 ,philosophical ,transactions of the ,royal ,society of ,london4 ,pogg4 ,ann4 ,poggendorff's ,annalen der ,physik und ,chemie4 ,proc4 ,amer4 ,acad4 ,proceedings of the ,american ,academy4 ,proc4 ,chem4 ,soc4 ,proceedings of the ,chemical ,society4 ,proc4 ,roy4 ,soc4 ,proceedings of the ,royal ,society4 ,prog4 ,age ,progressive ,age 7now ,gas ,age74 ,publ4 ,astrophys4 ,observ4 ,publikationen des ,astrophysikalischen ,potsdam ,observatoriums zu ,potsdam4 ,schweigg4 ,j4 ,schweigger's ,journal fr ,chemie und ,physik4 ,sitzungsber4 kaiserl4 ,akad4 ,sitzungsberichte der kaiserlich ,akademie ,wiss4 ,wien der ,wissenschaften zu ,wien4 ,sitzungsber4 knigl4 ,akad4 ,sitzungsberichte der kniglich ,akademie ,preussischen ,wiss4 ,berlin der ,wissenschaften zu ,berlin4 ,stahl ,eisen ,stahl und ,eisen4 ,trans4 ,amer4 ,el4 chem4 ,soc4 ,transactions of the ,american ,electrochemical ,society4 ,trans4 ,amer4 ,inst4 ,min4 ,transactions of the ,american ,institute ,eng4 of ,mining ,engineers4 ,trans4 ,chem4 ,soc4 ,transactions of the ,chemical ,society4 ,tsch4 ,min4 ,mitt4 ,tschermak's ,mineralogische ,mittheilungen4 ,u4 ,s4 ,geol4 ,survey ,united ,states ,geological ,survey--,mineral ,resources of the ,united ,states4 ,u4 ,s4 ,p4 ,united ,states ,patent ,specification4 ,zeitsch4 anal4 ,chem4 ,zeitschrift fr analytische ,chemie4 ,zeitsch4 angew4 ,chem4 ,zeitschrift fr angewandte ,chemie4 ,zeitsch4 anorg4 ,chem4 ,zeitschrift fr anorganische ,chemie4 ,zeitsch4 ,elektrochem4 ,zeitschrift fr ,elektrochemie4 ,zeitsch4 ,kryst4 ,min4 ,zeitschrift fr ,krystallographie und ,mineralogie4 ,zeitsch4 physikal4 ,chem4 ,zeitschrift fr physikalische ,chemie1 ,stchiometrie und ,verwandtschaftslehre4 ,zeitsch4 pr4 ,geol4 ,zeitschrift fr praktische ,geologie4 ,zeitsch4 wiss4 ,photochem4 ,zeitschrift fr wissenschaftliche ,photographie1 ,photophysik und ,photochemie4 ,,introduction ,by ,,sir ,,william ,,crookes1 ,o4,m41 ,f4,e4,s4 ,the mysterious group of substances to which have been given the title of 8rare earths0 has long been the subject of my special study1 and no one knows better the magnitude of the difficulties encountered in the investigation1 or realises more clearly the comparative insignificance of the knowledge we have acquired4 ,the rare earths constitute the most striking example of the association of chemical substances with others which are closely allied to themselves1 and from which they are separable only with extreme difficulty4 ,they form a group to themselves1 sharply demarcated from the other elements1 and it is my belief that by following the study of them to the utmost limits1 we may arrive at the explanation of what the chemical elements really are and how they originated1 and discover the reasons for their properties and mutual relations4 ,when this knowledge has been wrested from ,nature chemistry will be established upon an entirely new basis4 ,we shall be set free from the need for experiment1 knowing a priori what the result of each and every experiment must be2 and our knowledge then will as much transcend our present scientific systems as the knowledge of the skilled mathematician of the present day exceeds that of primitive man1 counting upon his fingers4 ,the great problem of the nature and genesis of the elements is approaching solution1 and when the consummation is reached it will undoubtedly be found that the study of the rare earths has been an important factor in bringing it about4 ,there has long been a need for a work in the ,english language dealing historically and descriptively with these substances1 and ,mr4 ,levy's book is well fitted to fill the gap4 ,the chapters on the technical applications of the rare earths are particularly valuable1 and the chemical aspect of the incandescent lighting industry is admirably treated4 ,the author is to be congratulated upon having successfully achieved an important and useful piece of work4 ,,william ,,crookes4 ,december #aiad4 ,,the ,,rare ,,earths ,,part ,i ,,occurrence ,,of ,,the ,,rare ,,earths ,,chapter ,i ,,the ,,nature ,,of ,,the ,,minerals ,,and ,,their ,,mode ,,of ,,occurrence ,the history of the rare earth minerals begins in the year #agea1 when the ,swedish mineralogist ,cronstedt described a new mineral1 which he had found intimately mixed with chalcopyrite#a in the quarry of ,bastns1 near ,ryddarhyttan1 in the province of ,westmannland1 ,sweden4 ,cronstedt gave the mineral the name ,tung-sten 7heavy stone72 but as the name ,tenn-spat 7heavy spar1 or heavy mineral7 had already been selected by ,wallerius 7#agdg7 for a new species from ,bohemia1 believed to contain tin1 the choice was not a happy one4 ,more than fifty years after its discovery1 a new earth1 now known as ceria1 was isolated from ,cronstedt's mineral1 for which at the same time the name ,cerite was proposed4#b ,meanwhile1 however1 the ,finnish chemist ,johann ,gadolin had observed1 in the year #agid1 a new earth in a mineral discovered by ,arrhenius at ,ytterby in ,sweden in #aghh2 he called the new oxide ,ytterbia1 and the mineral in which he observed it1 ,ytterbite4 ,the discovery was confirmed in #agig by ,ekeberg1 who suggested the names ,yttria and ,gadolinite for the oxide and mineral respectively2 these names were accepted by ,klaproth1 and soon came into general use4#c ,whilst then ,cerite was the first of the rare earth minerals to be discovered1 it was in ,gadolinite that new elements were first recognised1 and the chemistry of the rare earths began in #agid with ,gadolin's observation4 #a ,chalcopyrite1 or ,copper pyrites1 is a mixed sulphide of iron and copper1 of the approximate formula ,cu,fe,s4 #b ,for the history of the name ,tungsten1 see under the mineral ,cerite1 ,ch4 ,,ii4 #c ,the history of these names will be found somewhat more fully under ,gadolinite1 ,ch4 ,,ii4 ,during the nineteenth century a considerable number of rare earth minerals was discovered and analysed2 the quantities of the minerals observed1 however1 were so small that the name #8,rare earths1' applied to the new oxides found1 was in every sense justified4 ,until the year #ahhe1 though by that time the scientific interest of the group had been fully demonstrated by the discovery of several new elements1 it was supposed that the minerals were almost entirely confined to a few scattered localities in ,scandinavia and the ,ural mountains4 ,in that year ,dr4 ,auer von ,welsbach announced his application of the rare earths to the manufacture of incandescent mantles4 ,immediately there was a great demand for raw material for the preparation of thoria and ceria4 ,the agents of the ,welsbach ,company visited all the important mining centres of ,europe and ,america1 intent on a search which shortly made it clear that the metals of the so-called #8rare earths' are really quite widely distributed in nature4 ,the chief commercial deposits are the monazite sands of the ,carolinas1 the ,idaho basin1 and ,brazil1 the gem-gravels of ,ceylon1 and the remarkable deposits of gadolinite and allied minerals at ,barringer ,hill in ,texas4 ,whilst deposits of commercial importance are not very common1 improved scientific methods and more careful search have shown that in traces the rare earths are of exceedingly wide distribution4 ,sir ,william ,crookes has shown that yttria earths are often present in calcite and in coral2 whilst ,headden#d noted that quite considerable amounts 7up to #jjc per cent47 were present in a yellow phosphorescent variety of calcite from ,colorado4 ,similarly ,humphreys#e found that fluorspar usually contains traces of yttrium1 whilst one or two phosphorescent varieties contain quantities varying up to #jje per cent4 ,the presence of yttria elements in phosphorescent varieties of calcite is interesting1 and some connection has been suggested2 there is1 however1 no positive ground for the belief in such a relation4 #d ,amer4 ,j4 ,sci41 #aijf1 iv41 #ba1 #cja4 #e ,astrophys4 ,j41 #aijd1 #bj1 #bff4 ,more recently ,eberhard#f has found very considerable quantities of rare earths in cassiterite 7tin dioxide1 ,sn,o7 and wolframite an iron manganese tungstate1 7,fe1,mn7,,wo4 ,a specimen of wolframite from the ,erzgebirge was found to contain nearly #jd per cent4 of rare earths1 over half of this quantity being scandium oxide4 ,a process which is readily susceptible of commercial application has been worked out by ,r4 ,j4 ,meyer1#g for the extraction of scandia and the yttria earths from the mixed oxides left after the treatment of wolframite for tungstic acid4 #f ,sitzungsber4 knigl4 ,akad4 ,wiss4 ,berlin1 #aijh1 #hea2 #aiaj1 #djd4 #g ,meyer1 ,zeitsch4 anorg4 ,chem41 #aijh1 #fj1 #acd4 ,meyer und ,winter1 ibid41 #aiaj1 #fg1 #cih4 ,using the spectroscopic method1 which is capable of detecting one part of scandia in twenty thousand1 ,eberhard 7loc4 cit47 has found that minute quantities of scandia and yttria earths are present in almost all the commoner rocks and minerals4 ,the minerals richest in scandium were beryl1 cassiterite1 wolfram1 the zircon minerals1 and the titanates and columbates of the ceria and yttria oxides4 ,these results are in agreement with the observations of ,sir ,william ,crookes1#h who has made the study of scandium especially his own4 ,from the fact that scandium was often observed unaccompanied by any other member of the rare earth group1 ,eberhard rather favours ,urbain's conclusion#i that scandium may not be a member of the rare earth family4 ,spectroscopic examination has also shown the existence of some of the rare earth elements in the sun and stars 7see ,europium1 p4 #ahi74 #h ,phil4 ,trans4 #aiaj1 ,a1 #baj1 #cei4 #i ,see under ,scandium in ,pt4 ,,ii4 ,in view of this extraordinarily wide distribution of the rare earths in the mineral world1 it is but natural that they should be found also in the vegetable and animal kingdoms4 ,tschernik#aj found #aj per cent4 of rare earths in the ash of a coal from ,kutais1 in the ,caucasus1 and smaller quantities have been found in the ashes of various plants2 members of the group have also been identified in the human body4 #aj ,see ,abstr4 in ,zeitsch4 ,kryst4 ,min41 #ahii1 #ca1 #eac4 ,apart from the general occurrence in traces throughout the mineral kingdom1 the minerals in which the rare earths occur are not very common2 and though of fairly wide distribution1 they are found usually only in small quantities4 ,the earliest known locality1 and the most fruitful in regard to number of species1 has been the southern part of the ,scandinavian peninsula2#aa the minerals occur in the numerous pegmatite veins traversing the granitic country-rock4 ,the mining district round ,miask1 in the ,ural mountains1 has also long been known as a fruitful source4 ,other districts in ,europe are the ,harz and ,erzgebirge1 the ,laacher ,see in ,prussia1 ,joachimsthal in ,bohemia1 ,dauphin1 ,cornwall1 etc4 ,in the ,united ,states numerous localities are known2 the chief are in the ,carolinas and ,georgia1 ,idaho1 ,oregon1 ,california1 ,texas1 ,colorado1 ,virginia1 ,pennsylvania and ,connecticut4 ,many of the southern provinces of ,brazil also furnish important sources2 the famous diamond fields of ,minas ,geraes1 ,matto-,grosso1 ,goyaz and the surrounding provinces yield numerous species1 whilst the sands along the southern coasts of ,bahia are rich in monazite1 and form to-day the most important source of the mineral4 ,monazite1 as well as other rare earth minerals1 occurs also in ,south ,africa4 ,an interesting species1 plumboniobite 7q4v471 has recently been found in ,german ,east ,africa4 ,from ,australia numerous occurrences are reported1 whilst in ,canada only a few districts are known to yield members of the group4 ,in ,asia important localities are ,ceylon--the famous gem-gravels being the most accessible source--and one or two districts in ,japan2 monazite has been reported recently in considerable quantities near ,travancore1 ,india4#ab ,a more extended search will doubtless show that they occur in many other places4 #aa ,see ,brgger1 ,die ,mineralien der ,sd-,norwegische ,granit-,pegmatitgnge1 ,christiania1 #aijf4 #ab ,bull4 ,imp4 ,inst41 #aiaa1 vol4 ix2 ,no4 #b1 p4 #ajc4 ,for several reasons1 the rare earth minerals#ac form a group of the highest scientific interest4 ,in the first place1 they are generally of very complex composition1 more especially with regard to their rare earth content4 ,thus1 whilst it sometimes happens that one or other of the two groups of oxides 7the ceria and yttria groups7 may predominate to the complete exclusion of the second1 it is no uncommon thing for a species to contain almost all the elements of the rare earth family4 ,on the other hand1 it is very uncommon for as much as #ej per cent4 of the rare earth content to consist of any one oxide4 ,the usual case is that a mineral contains chiefly yttria earths with some ceria earths1 or vice vers1 the two sub-groups being almost always complex mixtures of several oxides1 in which occasionally one may predominate4 ,the remarkable similarity in chemical behaviour of the rare earth elements1 and the difficulty of separating them1 correspond to this peculiarity in their occurrence4 #ac ,the phrase #8rare earth minerals' will be used whenever it is desired to indicate collectively those minerals of which the yttria and ceria earths form an important constituent1 as contrasted to those in which only traces of these oxides occur4 ,such minerals may often contain titanium1 zirconium1 or thorium1 and1 for convenience1 the term may be taken to include the commoner zirconium and thorium minerals1 but not the commoner titanium minerals4 ,a second point of even greater interest is that the rare earth minerals are as a general rule strongly radio-active2 further1 it only occasionally happens that any mineral in which the rare earths do not form an important constituent has more than the feeblest activity2 the exceptions being1 of course1 those uranium minerals which do not contain rare earths4 ,the connection may be pushed even further2 for whilst it appears that hardly any rock or mineral possesses absolutely no radio-activity1 it is equally worthy of notice that traces of the rare earths1 if not quite universal in the mineral world1 are yet normally found in the majority of common minerals4 ,as a natural consequence of their activity1 the rare earth minerals are also as a rule rich in helium4 ,these facts and the problems which they open up will be treated more fully in a later chapter4 ,a point of further interest is that of the age of the rare earth minerals4 ,except in a few cases where they are obviously of secondary formation1 these minerals are among the oldest known to us4 ,they occur usually in igneous rocks1 particularly in granites which have been considerably metamorphosed4 ,where erosion has occurred1 they are found in deposits of such a nature as to leave very little doubt that the original rock was of plutonic formation and of very considerable age4 ,whilst it is true1 however1 that the rare earth minerals are generally of very great antiquity 7none of the primary minerals being of more recent date than the palozoic age71 ,eberhard has pointed out that the age and nature of common rocks seem to have absolutely no influence on the traces of scandia and yttria oxides which they contain4 ,the geological evidence shows that the rare earth minerals are on the whole exceedingly stable1 and that they have been generally formed during the pegmatitic alteration of granites4 ,as early as the year #ahdj1 ,scheerer drew attention to these facts1 and to the extreme age of the rare earth minerals2 but so far his observation seems to have attracted little attention1 and no explanation has been put forward4 99 99 99 99 99 ,in the following chapters no attempt is made to treat the rare earth minerals fully4 ,an alphabetical list of all the minerals of any importance which contain rare earths1 titanium1 zirconium or thorium is given1 and of these several are selected for fuller treatment4 ,the basis of selection has been somewhat arbitrary4 ,those species which are of mineralogical importance1 as well as those to which any special historical1 scientific or commercial interest attaches1 have of course been singled out2 in addition1 the more recently discovered species have occasionally been considered worthy of separate mention4#ad #ad ,a full list of the minerals containing rare earths known up to #aijd1 with an account of their properties and very full references1 will be found in the work of ,dr4 ,j4 ,schilling1 ,das ,vorkommen der ,seltenen ,erden im ,mineralreiche1 #aijd4 ,it is now being realised that some knowledge of crystallography is essential to the chemist1 and for this reason short accounts of the crystallography of the selected types have been given4 ,apart from this1 every effort has been made to render the mineralogy intelligible to the student of chemistry who has devoted no attention previously to this subject1 and also to stimulate an interest in the problems of mineral chemistry1 unfortunately too often ignored by our present-day teachers4 ,the rare earth minerals afford good examples of some phenomena of great interest to the chemist1 as1 e4g4 ,isomorphism and ,solid ,solution1 ,dimorphism1 ,isodimorphism1 and ,molecular ,change1 and in one or two cases these are treated rather fully4 ,no special advantages are claimed for the system of classification1 which is merely one of convenience4 ,the minerals are divided into five groups3-- 7#a7 ,the ,silicates1 which are grouped into three sub-divisions4 7#b7 ,the ,titano-silicates and the ,titanates4 7#c7 ,the ,tantalo-columbates1 sub-divided into those free from titanium and those in which titanium is present4 7#d7 ,the ,oxides and ,carbonates4 7#e7 ,the ,halides and ,phosphates4 ,a separate chapter has been devoted to the monazite sands1 and another to the radio-active properties of the minerals4 ,,alphabetical ,,list ,,of ,,minerals ,,containing ,,titanium1 ,,zirconium1 ,,thorium1 ,,or ,,elements ,,of ,,the ,,cerium ,,and ,,yttrium ,,groups4 ,the following list contains all but a few entirely unimportant members of these classes of minerals4 ,the names of those species selected for fuller treatment are printed in heavy type1 whilst names of those not so selected1 which for convenience are included under the generic term #8,rare earth mineral1' i4e4 roughly all those containing ,thorium1 or elements of the ,cerium and ,yttrium groups1 and the commoner ,zirconium minerals1 as distinguished from minerals containing ,titanium1 are printed in italics4 7,see footnote on p4 #d47 ,their properties are given in the following order3-- ,chemical ,composition and ,rare ,earth ,content4 ,crystallographic ,data4 ,physical ,properties4 ,locality1 etc4 ,the following contractions are employed3 ,e any element or elements of the cerium or yttrium groups4 ,cer oxides of the cerium metals4 ,yttr oxides of the yttrium metals4 ,g ,specific ,gravity4 ,h ,hardness4 ,aenigmatite4 ,a ,titanosilicate of ,fe and ,na1 with small proportions of ,fe and ,al4 ,closely allied to the amphiboles4 ,ti,o #g-h4 ,anorthic4 ,habit prismatic4 ,g #chj-chf4 ,h #e4 ,black2 pleochroism strong4 ,greenland and ,s4 ,norway4 ,aeschynite ,a ,titanocolumbate of ,cerium metals1 with ,th1 ,fe1 ,ca1 ,mn1 aq4 ,cer #aid-bda2 ,yttr #aa-ca2 ,th,o #aeg-agf2 ,ti,o #ba-bb4 ,rhombic1 holosymmetric4 ,habit prismatic or tabular4 ,g #di-eg4 ,h #ef4 ,black2 opaque4 ,hitter1 ,norway2 ,miask1 ,urals2 also in ,germany and ,brazil4 ,allanite 7,orthite74 ,h,o1 #d,r,o1 #c,r,o1 #f,si,o1 where ,r ,ca1 ,fe1 ,be1 and ,r ,al1 ,fe1 ,e4 ,an epidote containing rare earths4 ,cer #cf-ea 7usually #aj-be72 ,yttr #j-h 7usually #c72 ,th,o #j-ce4 ,monoclinic2 isomorphous with epidote4 ,g #ce-db4 ,h #e-f4 ,brown to black2 opaque4 ,widely distributed in ,greenland and ,scandinavia4 ,alvite 7,anderbergite74 ,silicate of ,zr and ,e1 with ,ca1 ,mg1 ,be1 ,al1 ,cu1 ,zn1 and aq4 in small quantities4 ,cer #cih2 ,yttr #bb2 ,zr,o #cje-fad4 ,tetragonal2 optically isotropic4 ,pseudomorphous after zircon4 ,g #cc-dc4 ,h #e-f4 ,yellowish brown2 transparent4 ,ytterby1 ,sweden2 ,arendal1 ,norway2 various localities in ,n4 ,america4 ,anatase 7,octahedrite74 ,titanium dioxide4 ,ti,o #ig-ajj4 ,tetragonal2 habit octahedral4 ,g #chb-cie4 ,h #e-f4 ,transparent to opaque2 brown to black4 ,dauphin2 ,bavaria2 ,cornwall2 ,norway2 ,brazil1 etc4 ,ancylite4 #d;,ce7,,oh7,,co #c,sr,c,o #c;,h,o2 with ,fe1 ,mn1 ,ca1 ,f1 traces4 ,cer #dfc4 ,rhombic2 prismatic4 ,g #cie4 ,h #d4 ,brown2 translucent4 ,plain of ,narsarsuk1 ,greenland4 ,annerdite4 ,a parallel growth of ,columbite on ,samarskite1 once believed to be a new species4 ,corresponding to ,columbite4 ,arfvedsonite4 ,metasilicate of ,na1 ,ca1 ,fe1 ,zr2 approximately #d,na,o1#c;,ca,o1#ad;,fe,o17,al1,fe7,o1# ba,si,o4 ,zr,o #a-f4 ,monoclinic--an amphibole4 ,g #cdd4 ,h #f4 ,black2 pleochroism strong4 ,s4 ,greenland and ,s4 ,norway4 ,arizonite4 ,ferric metatitanate1 ,fe,o1#c,ti,o or ,fe7,ti,o74 ,ti,o #cfg4 ,uncertain2 apparently monoclinic4 ,g #dbe4 ,h #f-g4 ,dark steel-grey2 opaque4 ,hackberry1 ,arizona4 ,arrhenite4 ,silico-tantalate of ,yttrium metals1 with ,ce1 ,al1 ,fe1 ,ca1 ,be1 aq4 ,yttr #ccb2 ,cer #bf2 ,zr,o #cd4 ,amorphous4 ,g #cfh4 ,red2 translucent to opaque4 ,ytterby1 ,sweden4 ,astrophyllite4 ,titano-silicate of ,fe1 ,al1 ,mn1 ,zr1 ,k1 ,na1 with aq4 ,zr,o #ab-de2 ,ti,o #g-ad4 ,rhombic4 ,cleavage 7#jaj7 perfect4 ,g #cb-cd4 ,h #c4 ,golden to bronze yellow2 strongly pleochroic4 ,brevik1 ,norway2 ,el ,caso ,co41 ,colorado2 ,greenland4 ,auerbachite4 ,an impure hydrated form of ,zircon1 ,zr,si,o4 ,zr,o #eeb4 ,tetragonal2 isotropic4 ,pseudomorphous after zircon4 ,g #djf4 ,h #f4 ,brownish-grey2 translucent to opaque4 ,alexandrovsk1 ,russia4 ,auerlite4 #c,th,o1#c,si,o1,p,o#f;,h,o2 traces of ,fe1 ,ca1 ,mg1 ,al1 ,,co1 etc4 ,si,o replaced by ,p,o_/#c8 ,th,o #fib-gbb4 ,tetragonal2 probably a pseudomorph after ,thorite4 ,g #dd-dh4 ,h #b-c4 ,yellowish to orange-red4 ,henderson ,co41 ,n4 ,carolina4 ,baddeleyite4 ,zr,o1 with small amounts of ,si,o1 ,fe,o1 ,al,o1 ,ca,o1 etc4 ,zr,o #ife4 ,monoclinic4 ,g #dd-fj4 ,h #f4 ,brown2 pleochroic4 ,so ,paulo1 ,brazil2 ,rakwana1 ,ceylon4 ,bagrationite4 ,a variety of ,allanite 7orthite7 with no important chemical difference4 ,monoclinic2 habit prismatic4 ,g #chd4 ,h #f4 ,black2 translucent to opaque4 ,achmatovsk1 ,urals4 ,bastnsite 7,harmatite74 ,hydrated fluocarbonate of ,cerium metals1 ,e7,f7,,co4 ,cer #fd-ice2 ,th,o #j-aj4 ,hexagonal prisms1 pseudomorphous after ,tysonite 7q4v472 or massive4 ,g #di-eb4 ,h #d-d4 ,yellow to brown2 transparent4 ,bastns1 ,sweden2 ,pike's ,peak1 ,colorado4 ,beckelite4 ,zirconosilicate of rare earths and lime1 ,ca,e7,si1,zr7,o4 ,cer #eig2 ,yttr #bh2 ,zr,o #be4 ,cubic1 in octahedra and dodecahedra4 ,cubic cleavage4 ,g #dae4 ,brown2 transparent4 ,near ,sea of ,azov1 ,russia4 ,benitoite4 ,a ,titano-silicate of barium1 ,ba,ti,si,o4 ,ti,o #bja4 ,rhombohedral4 ,h #f-g4 ,colourless to blue2 transparent2 pleochroism strong4 ,source of ,san ,benito ,river1 ,california4 ,blomstrandine4 ,dimorphous with ,polycrase 7q4v471 and of same composition4 ,orthorhombic2 isomorphous with priorite 7q4v474 ,g #de-ej2 ,h #f4 ,bright black2 translucent4 ,hitter and ,arendal1 ,norway4 ,blomstrandite4 ,hydrated titano-columbate of ,u1 with some ,fe and ,ca4 ,ti,o #ajg4 ,massive4 ,g #dag-dbe4 ,h #e4 ,black2 opaque4 ,nohl1 ,sweden4 ,bodenite4 ,a variety of ,allanite 7q4v471 rich in ,al and ,ca1 with no ,be4 ,yttr #ag2 ,cer #ah4 ,monoclinic4 ,as ,allanite4 ,boden1 near ,marienburg4 ,britholite4 ,a basic phosphosilicate of cerium metals1 with ,fe1 ,ca1 ,mg1 ,na1 ,f4 ,cer #fje-fji4 ,hexagonal2 habit prismatic4 ,g #dddf4 ,h #e4 ,brown2 transparent4 ,naujakasik1 ,greenland4 ,brggerite4 ,a variety of ,uraninite 7q4v471 with rare earths1 ,th1 ,pb1 ,fe1 ,ca1 ,si1 aq41 etc4 ,cer #jd2 ,yttr #ad-dc2 ,th,o #dg-fa4 ,traces of ,zr,o4 ,cubic1 in octahedra and dodecahedra4 ,g #hg-ij4 ,h #e-f4 ,black2 translucent to opaque4 ,annerd1 near ,moos1 ,norway4 ,brookite4 ,titanium dioxide1 ,ti,o #ii-ajj2 trimorphous with ,anatase and ,rutile4 ,orthorhombic4 ,g #chg-dja4 ,h #e-f4 ,brown2 opaque4 ,dauphin2 ,urals2 ,switzerland2 ,magnet ,cove1 ,arkansas4 ,calciothorite4 ,a variety of ,thorite containing lime--#e,th,si,o1#b;,ca,si,o #aj;,h,o4 ,th,o #eic4 ,completely amorphous4 ,g #daad4 ,h #d4 ,deep red2 translucent4 ,islands of ,lven and ,ar1 ,langesund ,fiord1 ,norway4 ,cappelenite4 ,a borosilicate of rare earth metals and barium1 with traces of ,th1 ,ca1 ,k1 ,na1 aq4 ,approximately ,ba,si,o1 ,,ybo4 ,cer #db2 ,yttr #ebe4 ,hexagonal2 habit prismatic4 ,g #ddjg4 ,h #f-f4 ,greenish brown2 translucent4 ,island of ,klein-,ar1 ,langesund ,fiord1 ,norway4 ,caryocerite 7,karyocerite74 ,complex fluosilicate of ,e1 with ,ta1 ,th1 ,ca2 also ,,co1 ,p,o1 ,b1 ,al1 ,fe1 ,mn1 ,u1 ,mg1 ,na1 aq41 etc4 ,approaching ,melanocerite1 7q4v471 but richer in ,th4 ,very complex4 ,cer #dah2 ,yttr #bb2 ,th,o #acf2 ,zr,o #je4 ,rhombohedral1 but isotropic2 apparently a pseudomorph after ,melanocerite 7q4v47 ,g #dbie4 ,h #e-f4 ,nut brown2 translucent4 ,faces very brilliant1 but striated4 ,lustre vitreous to resinous4 ,various rocks and shoals round ,ar ,island1 ,langesund ,fiord1 ,norway4 ,castelnaudite4 ,a variety of ,xenotime 7q4v47 containing ,zr4 ,yttr #fjd2 ,zr,o #gd4 ,tetragonal4 ,g #de4 ,h #d-e4 ,greyish white to pale yellow4 ,diamond sands of ,brazil4 ,cataplejite 7,kataplejite74 ,h7,na1,ca7,zr,si,o4 ,zr,o #bif-dj 7usually #cj-cc74 ,monoclinic1 pseudohexagonal4 ,becomes truly hexagonal at #adj;,c4 ,g #bh4 ,h #f4 ,yellow to brown2 transparent to opaque4 ,a blue variety is known which contains no calcium4 ,islands of ,langesund ,fiord1 ,norway2 ,narsarsuk1 ,greenland4 ,cerite4 ,a basic silicate of ,cerium metals1 with ,ca and ,fe4 ,approximately ,h7,ca1,fe7,ce,si,o4 ,cer #ejg-gah4 ,in a variety from ,batoum1 ,tschermak reports ,yttr #gf and ,zr,o #aag4 ,orthorhombic2 usually massive or granular4 ,g #di4 ,h #e-f4 ,brown to red2 translucent to opaque4 ,ryddarhyttan1 ,sweden2 ,batoum1 ,caucasus8 ,chalcolamprite4 ,a silico-columbate of ,e1 ,zr1 ,ca1 ,fe1 ,na1 ,k2 ,r,cb,f,si,o1 where ,r represents various metals4 ,e #cda2 ,zr,o #eg4 ,cubic1 in small octahedra4 ,g #cgg4 ,h #e4 ,greenish brown2 opaque4 ,metallic lustre 7 ,copper1 lustre74 ,narsarsuk1 ,s4 ,greenland4 ,churchite4 ,hydrous phosphate of ,cerium metals and ,ca2 ,cer #eahg4 ,monoclinic8 ,allegations only4 ,g #cad4 ,h #c4 ,greyish2 transparent to translucent4 ,cornwall4 ,cleveite4 ,a variety of ,uraninite 7q4v47 rich in rare earths and helium4 ,cer #bc-bi2 ,yttr #ajj-ajc2 ,th,o #df-dh4 ,cubic2 usually massive4 ,g #gdi4 ,h #e4 ,black2 opaque4 ,arendal1 ,norway4 ,cordylite4 ,fluocarbonate of ,cerium metals and ,ba2 ,e,f,ba7,,co74 ,cer #did4 ,hexagonal2 isomorphous with ,parisite 7q4v474 ,g #dca4 ,h #d4 ,yellow2 transparent4 ,plain of ,narsarsuk1 ,greenland4 ,cossyrite4 ,a variety of ,aenigmatite 7q4v47 of very complex composition1 ,ti,o #f-h4 ,anorthic4 ,g #cgd4 ,h #e4 ,black2 opaque4 ,island of ,pantellaria 7formerly ,cossyra74 ,cyrtolite4 ,a pseudomorph after zircon1 allied to ,alvite 7q4v474 ,tetragonal4 ,see ,alvite4 ,various localities in ,scandinavia1 and ,u4,s4,a4 ,davidite4 ,a ,titanate of ,fe1 ,u1 ,v1 ,cr1 and ,e--uncertain formula4 ,ti,o #ej2 ,e,o #e-aj4 ,cubic--in grains and rounded crystals4 ,g #d about4 ,black1 with brilliant lustre4 ,olary1 ,s4 ,australia4 ,delorenzite4 #b;,fe,o1,,uo1#b,y,o1#bd,ti,o4 ,yttr #adfc2 ,ti,o #ee4 ,rhombic2 habit prismatic4 ,g #dg4 ,h #e-f4 ,black2 translucent to opaque2 lustrous4 ,craveggia1 ,piedmont1 ,italy4 ,derbylite4 ,fe,o1,sb,o #e;,fe,o1,ti,o8 ,ti,o #ce about4 ,orthorhombic2 habit prismatic4 ,g #dec4 ,h #e4 ,pitch black2 opaque2 lustre resinous4 ,tripuhy1 ,minas ,geraes1 ,brazil4 ,dysanalyte 7,perovskite74 ,approximately #f,r,ti,o1,r7,cb1,ta7,o1 where ,r ,ca1 ,fe4 ,believed by ,hauser to be merely an impure ,perovskite 7q4v474 ,cer #j-ea2 ,ti,o #dae-eic4 ,cubic4 ,g #dac4 ,h #e-f4 ,black2 opaque4 ,vogtsburg1 near ,baden1 ,germany4 ,elpidite4 ,na,zr7,si,o71 #a;,h,o4 ,zr,o #bje4 ,orthorhombic4 ,g #beb-bef4 ,h #g-h4 ,colourless to red2 translucent4 ,various localities in ,greenland4 ,endeiolite4 ,r,cb,o7,,oh7 ,r,si,o 7cf4 ,chalcolamprite74 ,e,o #ddc2 ,zr,o #cgh4 ,cubic4 ,g #cdd4 ,h #d4 ,dark chocolate-brown2 transparent4 ,narsarsuk1 ,greenland4 ,erdmannite 7,michaelsonite74 ,a silicate of ,e and ,ca1 with ,zr1 ,be1 ,th1 ,al1 ,fe1 aq41 etc4 ,an altered ,homilite8 ,cer #agg-cdi2 ,yttr #ad-ba2 ,th,o ,zr,o #j-ab4 ,amorphous2 isotropic4 ,g #cja-cci4 ,h #d4 ,brown to leek-green4 ,near ,brevig1 ,norway4 ,erikite4 ,a phosphosilicate of ,e1 ,ca1 ,al1 ,k and ,na1 with ,th,o1 ,h,o1 etc4 ,cer #dje2 ,th,o #cc4 ,orthorhombic4 ,g #cdgc4 ,h #e-f4 ,brown2 opaque4 ,julianehaab1 ,greenland4 ,eucolyte4 ,r,r,zr7,si,o71 where ,r ,k1 ,na1 ,h1 and ,r ,ce7,,oh71 ,fe1 ,mn1 ,ca1 and ,zr7,o,cl7 may replace ,si,o8 ,a very complex mineral4 ,zr,o #aji-bj2 ,cer #j-eb4 ,rhombohedral4 ,g #cj-ca4 ,h #e-e4 ,red to brown2 translucent4 ,double ,refraction strong1 -ve4 ,various localities in ,norway4 ,eucrasite4 ,an altered ,thorite 7q4v47 containing ,e1 ,ca1 ,fe1 ,mn1 ,na1 ,ti1 ,h,o1 etc4 ,cer #ad2 ,yttr #ei2 ,th,o #cfj2 ,zr,o #jf4 ,rhombic 7,paijkull74 ,amorphous1 isotropic 7,brgger74 ,g #dci4 ,h #d-e4 ,brownish black2 opaque4 ,near ,brevig1 ,norway4 ,eudialite4 ,a variety of ,eucolyte 7q4v47 of the same composition4 ,as ,eucolyte4 ,g #bib4 ,double ,refraction strong1 ve4 ,otherwise as ,eucolyte4 ,greenland2 ,lapland2 ,arkansas1 ,u4,s4,a4 ,euxenite4 ,e7,cb,o71,e7,ti,o71#a;,h,o2 with ,u and ,zr4 ,cer #bc-hd2 ,yttr #acb-cdf2 ,ti,o #bj-bc4 ,th,o ,zr,o usually in traces4 ,orthorhombic2 usually massive4 ,g #df-ej4 ,h #f4 ,brownish-black2 translucent to opaque4 ,hitter1 ,brevig1 ,jolster1 ,arendal1 ,norway2 ,cooglegong1 ,australia2 ,n4 ,carolina4 ,fergusonite4 ,approximately ,e,o1 7,cb1,ta7,o1 with ,u1 ,fe1 ,ca4 ,cer #je-aci2 ,yttr #bgi-dga2 ,th,o ,zr,o #j-g4 ,berzelius found ,cer #cfc2 ,yttr #j in one specimen4 ,tetragonal1 polar4 ,g #ehd-dc when largely hydrated4 ,h #ef4 ,brown to black4 ,norway2 ,australia2 ,texas1 etc4 ,florencite4 ,a silico-phosphate of ,e and ,al4 ,cer #bh approximately4 ,g #cf4 ,h #e4 ,yellow to red4 ,resinous lustre4 ,minas ,geraes and diamond localities in ,brazil4 ,fluocerite4 ,basic fluoride of rare earth metals1 ,e,o1#d;,,ef4 ,cer #had-hbf2 ,yttr #aa-dc4 ,massive4 ,original hexagonal mineral of ,berzelius and ,haidinger1 probably ,tysonite 7q4v474 ,g #eg-ei4 ,h #d4 ,reddish yellow2 opaque4 sterby1 ,sweden4 ,freyalite4 ,silicate of ,e and ,th1 with ,al1 ,fe1 ,mn1 ,na1 aq41 etc4 ,cer #cac2 ,th,o #bhd2 ,zr,o #fc4 ,amorphous4 ,g #djf-dag4 ,h #f4 ,brown2 opaque2 lustre resinous4 ,brevig1 ,norway4 ,gadolinite4 ,fe,o1 #b;,be,o1 ,y,o1 #b,si,o1 where ,y yttrium metals4 ,cer #cd-eae 7usual #f-bj72 ,yttr #e-fj 7usual #ce-dh74 ,monoclinic2 habit prismatic4 ,often amorphous and isotropic4 ,g #dj-de4 ,h #f-g4 ,brown and green4 ,double ,refraction strong1 ve4 ,ytterby and ,fahlun1 ,sweden2 ,hitter and ,mal1 ,norway2 ,llano ,co41 ,texas2 ,colorado1 etc4 ,geikielite4 7,mg1,fe7,ti,o4 ,ti,o #efa-fdh4 ,specimens rich in iron are called ,picroilmenite4 ,massive4 ,g #d about4 ,h #f4 ,purplish or brownish black4 ,ceylon4 ,gorceixite4 ,an alumino-phosphate of alkaline and ceria earths4 ,cer #j-c4 ,microcrystalline4 ,g #c4 ,h #f4 ,white to brown4 ,translucent4 ,diamond sands of ,brazil4 ,guarinite4 ,formerly supposed to be dimorphous with ,titanite 7q4v472 shown by ,zambonini and ,prior 7#aiji7 to be identical with ,hiortdahlite 7q4v474 ,hainite4 ,tantalo-silicate and titanate of ,zr1 ,ca1 ,na4 ,zr,o #bi-cb4 ,anorthic4 ,g #cb4 ,h #e4 ,colourless to yellow2 transparent4 ,bohemia4 ,hellandite4 #c;,h#j1 #b,r,o1 #c,r,o1 #d,si,o1 where ,r ,ca1 ,mg1 ,th_/#b2 ,r ,e1 ,al1 ,fe1 ,mn4 ,e,o #dj4 ,monoclinic2 habit prismatic4 ,g #cgj4 ,h #e4 ,reddish-brown when fresh4 ,lindvikskollan and ,krager1 ,norway4 ,hiortdahlite4 #c;,ca,si,o1,ca7,f1,,oh7,na,zr,o4 ,zr,o #bae2 ,ti,o #ae4 ,anorthic2 habit tabular4 ,g #cbg2 ,h #e-e4 ,yellow1 with weak pleochroism4 ,island of ,lven1 ,langesund ,fiord1 ,norway4 ,hjelmite 7,hielmite74 ,a stanno-tantalate of ,ca1 ,mn1 ,fe1 ,e1 related to ,yttrotantalite 7q4v474 ,e,o #a-f4 ,orthorhombic4 ,g #ehb4 ,h #e4 ,black2 lustre metallic4 ,fahlun1 ,sweden4 ,homilite4 7,ca1,fe77,,bo77,si,o74 ,sometimes with ceria earths1 #j-bf4 ,monoclinic--isomorphous with ,gadolinite 78 ,brgger74 ,g #ccd-cch4 ,h #d-e4 ,black2 pleochroic4 ,islands of ,lanegsund ,fiord1 ,norway4 ,hussakite 7,xenotime74 ,a prismatic form of ,xenotime 7q4v471 erroneously supposed to contain #f ,,so4 ,diamond sands of ,brazil4 ,hydrotitanite4 ,an altered ,perovskite 7q4v47 with ,fe and aq4 ,ti,o #hbh4 ,amorphous4 ,g #cfh4 ,h #a-b4 ,yellowish grey4 ,magnet ,cove1 ,arkansas4 ,ilmenite4 ,fe,ti,o2 composition varies widely4 ,ti,o #ce-ebc4 ,rhombohedral4 ,g #de-e4 ,h #e-f4 ,black2 opaque4 ,slightly magnetic4 ,norway2 ,dauphin2 ,bohemia2 ,cornwall1 etc4 ,ilmenorutile4 ,fe,o1,nb,o1#e,ti,o8 ,ti,o #ff-ge4 ,tetragonal1 very near to ,rutile 7q4v474 ,g #dc-ej4 ,h #f-g4 ,brown to black2 opaque4 ,ilmen ,mountains1 ,russia4 ,johnstrupite4 ,silico-titanate of ,e1 ,al1 ,mg1 ,ca1 ,na1 etc41 with ,f and aq4 ,cer #ace2 ,yttr #aa2 ,ti,o #g-h2 ,th,o ,zr,o #cf4 ,monoclinic1 very close to ,epidote4 ,g #cai-cbi4 ,h #e4 ,brownish green2 weakly pleochroic4 ,islands of the ,langesund ,fiord1 ,norway4 ,kainosite 7,cenosite74 ,ca,y7,si,o71,ca,c,o1#b;,h,o1 where ,y ,yttrium metals4 ,yttr #cj-cg4 ,uncertain2 pseudo-hexagonal4 ,g #cch-cda4 ,h #e-f4 ,yellowish brown4 ,hitter and province of ,nordmark1 ,norway4 ,keilhauite 7,yttrotitanite74 ,an isomorphous mixture of ,titanite 7q4v47 with 7,e1,al1,fe7,si,o4 ,e,o #e-ab2 ,ti,o #bf-cj4 ,monoclinic2 isomorphous with ,titanite4 ,g #ceb-cgg4 ,h #f4 ,brown to black4 ,various localities in ,norway4 ,kischtimite4 ,a fluocarbonate of the ,cerium metals1 near ,parisite 7q4v474 ,cer #gdb4 ,massive4 ,g #dgh4 ,h #d4 ,yellowish brown2 translucent4 ,barsovka ,river1 ,kyshtymsk1 ,urals4 ,knopite4 ,a variety of ,perovskite 7q4v47 containing ,e and ,fe4 ,cer #d-g2 ,ti,o #ee4 ,pseudo-cubic4 ,g #db4 ,h #e4 ,grey2 opaque2 lustre metallic4 ,aln1 ,sweden4 ,kochelite4 ,a columbate of ,e1 ,fe1 ,zr2 with ,th,o1 ,si,o1 ,ca1 aq41 etc4 ,allied to ,fergusonite 7q4v474 ,yttr #agbb2 ,zr,o #abh2 ,th,o #abc4 ,doubtful2 may be tetragonal4 ,g #cgd4 ,h #c-c4 ,brown to honey yellow2 translucent4 ,the ,kochelweise1 near ,schreiberhau1 ,silesia4 ,koppite4 ,columbate of ,e1 ,ca1 ,fe1 ,th1 ,k1 ,na1 etc4 ,near ,pyrochlore 7q4v474 ,cer #d-aj2 ,zr,o #j-e4 ,cubic2 in dodecahedra4 ,g #dde-ddf4 ,h #e-f4 ,brown2 transparent4 ,schelingen1 ,black ,forest ,mountains1 ,germany4 ,lanthanite4 ,hydrated carbonate of ,cerium metals1 especially ,la2 ,e7,,co71#i;aq4 ,cer #edi4 ,orthorhombic2 habit tabular4 ,g #bf-bg4 ,h #b4 ,white2 opaque4 ,with ,cerite 7q4v47 at ,bastns1 ,sweden2 ,bethlehem1 ,pennsylvania1 ,u4,s4,a4 ,lavenite4 7,mn1,ca1,fe77,zr,o,f7,na7,si,o78 ,zr,o #bhh-caf4 ,monoclinic2 habit prismatic4 ,g #cea-cee4 ,h #f4 ,brown to yellow2 translucent4 ,langesund ,fiord1 ,norway2 the ,ardennes1 ,france4 ,leucosphenite4 ,ba,o1#b,na,o1#b7,ti1,zr7,o1#aj,si,o4 ,ti,o #acb2 ,zr,o #ce4 ,monoclinic2 wedge-shaped4 ,g #cje4 ,h #f4 ,white2 transparent4 ,narsarsuk1 ,greenland4 ,lewisite4 #c,r,sb,o1#b,r,ti,o1 where ,r ,ca1 ,fe and ,mn4 ,ti,o #aa-ab4 ,cubic2 in small octahedra4 ,g #die4 ,h #e4 ,yellow to brown2 translucent4 ,tripuhy1 ,minas ,geraes1 ,brazil4 ,loranskite4 ,tantalate of ,e1 ,zr1 ,fe1 etc4 ,yttr #aj2 ,cer #c2 ,zr,o #bj4 ,massive4 ,g #df4 ,h #e4 ,black2 opaque4 ,metallic lustre4 ,finland4 ,lorenzenite4 ,titano-silicate of ,na and ,zr2 ,ti,o #ce2 ,zr,o #ab4 ,orthorhombic2 acicular4 ,g #cd4 ,h #f4 ,colourless2 transparent4 ,south ,greenland4 ,mackintoshite4 ,mixture of oxides1 chiefly of ,th and ,u2 also ,fe1 ,ca1 ,mg1 ,pb1 ,na1 ,b1 ,ta1 etc4 ,composition very complex4 ,th,o #dec2 ,e,o #ai2 ,zr,o #a4 ,tetragonal1 resembling thorite 7q4v474 ,g #edb4 ,h #e4 ,black2 opaque4 ,bluffton1 ,llano ,co41 ,texas4 ,malacone4 ,an altered ,zircon 7q4v471 with ,e1 ,ca1 ,fe1 ,h,o1 etc4 ,zr,o #dg-fg4 ,tetragonal2 pseudomorphous4 ,g #ci-da4 ,h #f4 ,brown1 often dull white internally4 ,hitter1 ,norway2 ,haute ,loire1 ,france2 and in ,u4,s4,a4 ,mauzeliite4 ,very similar to ,lewisite 7q4v471 with ,pb4 ,ti,o #h4 ,cubic4 ,g #eaa4 ,h #e-f4 ,brown2 translucent4 ,jakobsberg1 ,sweden4 ,melanocerite4 ,very complex fluosilicate of ,e and ,ca1 chiefly4 ,cer #dh2 ,yttr #ib2 ,th,o ,zr,o #b4 ,rhombohedral2 habit tabular4 ,g #dac4 ,h #e-f4 ,deep brown to black4 ,transparent4 ,langesund ,fiord1 ,norway4 ,microlite4 ,complex columbate of ,ca1 ,e1 ,fe1 etc41 with ,f and ,h,o4 ,e,o #h4 ,cubic2 habit octahedral4 ,g #edh-eef4 ,h #e-e4 ,red to yellow4 ,stockholm1 ,sweden2 ,island of ,elba2 and in ,u4,s4,a4 ,molengraafite4 ,titano-silicate of ,ca1 ,na1 ,fe1 ,al1 ,mn1 etc4 ,ti,o #bh4 ,monoclinic2 in small prisms4 ,yellow4 ,high refraction and birefringence4 ,pilandsberg1 ,transvaal4 ,monazite4 ,phosphate of ,e1 with ,th and ,si,o4 ,cer #di-gd2 ,yttr #a-d2 ,th,o #a-bj4 ,monoclinic4 ,g #di-ec4 ,h #e-e4 ,red to brown and yellow2 translucent4 ,the ,carolinas2 ,idaho2 ,brazil2 ,scandinavia1 etc4 ,mosandrite4 ,in composition identical with ,johnstrupite 7q4v474 ,isomeric with ,johnstrupite 7q4v474 ,g #bic-cjc4 ,h #d4 ,reddish brown2 translucent4 ,langesund ,fiord1 ,norway4 ,muromontite4 ,a variety of ,allanite 7q4v471 rich in yttria earths and ,be1 but poor in ,al and ceria earths4 ,cer #ia2 ,yttr #cga4 ,see ,allanite4 ,g #dbfc4 ,h #g4 ,black to greenish black4 ,mauersberg1 ,erzgebirge1 ,saxony4 ,naegite4 ,a silicate of ,zr1 ,zr,si,o1 with ,e1 ,th1 ,u1 ,cb1 etc4 ,zr,o #eeb2 ,yttr #iab2 ,th,o #eja4 ,tetragonal2 in globular aggregates4 ,gr #djia4 ,h #g4 ,dark green or brown2 dull4 ,gravel-tin of ,japan4 ,narsarsukite4 ,na,fe,ti,si,o,f4 ,ti,o #ad4 ,tetragonal4 ,habit tabular4 ,gr #bge4 ,h #g-g4 ,yellow to reddish-brown2 pleochroic4 ,plain of ,narsarsuk1 ,greenland4 ,neptunite4 7,k1,na77,fe1,mg1,ca177,ti1,si7,o4 ,ti,o #ah4 ,monoclinic4 ,habit prismatic4 ,g #cbc4 ,h #e4 ,black1 red in flakes4 ,translucent to opaque4 ,narsarsuk1 ,greenland4 ,nivenite4 ,a variety of ,cleveite 7q4v471 readily soluble in dilute acids4 ,cubic2 crystallisation indistinct4 ,g #hja4 ,h #e4 ,velvet black2 opaque4 ,bluffton1 ,llano ,co41 ,texas4 ,nohlite4 ,a variety of ,samarskite 7q4v47 containing water 7 #df74 ,massive1 without cleavage4 ,g #ejd4 ,h #d-e4 ,brownish black2 opaque4 ,nohl1 near ,kongelf1 ,sweden4 ,oerstedite4 ,a variety of ,zircon 7q4v471 poor in ,si,o4 ,zr,o #fi4 ,tetragonal2 angles exactly those of ,zircon4 ,g #cfbi4 ,h #e4 ,reddish-brown2 adamantine lustre4 ,arendal1 ,norway4 ,orangite4 ,th,si,o1 usually with ,fe1 ,ca1 ,h,o in traces4 ,th,o #gab-gch4 ,tetragonal4 ,habit prismatic4 ,g #eai-edj4 ,h #d-e4 ,orange yellow2 lustrous4 ,see under ,thorite4 ,parisite4 ,e,ca,f7,,co74 ,cer #ejh-fdd2 ,yttr #j-be4 ,hexagonal4 ,habit pyramidal4 ,g #dcf4 ,h #d4 ,yellow to red2 transparent4 ,muso ,valley1 ,columbia2 ,montana1 ,u4,s4,a42 ,greenland2 ,norway2 the ,urals1 etc4 ,perovskite4 ,ca,ti,o1 with traces of ,fe4 ,ti,o #ehi4 ,pseudo-cubic8 ,optically biaxial4 ,g #djag4 ,h #e4 ,yellow2 transparent to opaque4 ,the ,urals2 ,switzerland2 ,tyrol1 etc4 ,pilbarite4 ,pb,o1,,uo1,th,o1#b,si,o1#b;,h#j #b;aq4 ,th,o #cac4 ,cer and ,yttr--traces4 ,amorphous4 ,g #dd-dg4 ,h #b-c4 ,bright yellow2 opaque4 ,pilbara goldfields1 ,west ,australia4 ,pitchblende4 ,a mixture of oxides1 chiefly ,,uo and ,,uo1 but without ,e,o or ,th,o4 ,amorphous4 ,g #e-fe4 ,h #c-d4 ,black2 resinous lustre4 ,bohemia2 ,cornwall2 ,carolina2 ,norway1 etc4 ,plumboniobite4 ,a variety of ,samarskite 7q4v47 containing ,pb2 ,r,cb,o1 ,r7,cb,o71 where ,r ,fe1 ,pb1 ,ca1 ,,uo1 ,r ,e1 ,al4 ,yttr #adc4 ,massive1 isotropic4 ,g #dhj-dha4 ,h #e-e4 ,dark brown to black4 ,morogoro1 ,uluguru ,mountains1 ,german ,e4 ,africa4 ,polycrase4 ,a titano-columbate of ,e and ,u2 ,yttr #aie-cbe2 ,ti,o #be-cc4 ,cer and ,th,o traces4 ,isomorphous with ,euxenite4 ,orthorhombic4 ,g #dj-dh4 ,h #f4 ,black2 vitreous lustre4 ,norway4 ,priorite4 ,dimorphous with ,euxenite 7q4v474 ,orthorhombic2 isomorphous with ,blomstrandine4 ,g #df-ej4 ,h #f4 ,black2 transparent in flakes4 ,swaziland1 ,s4 ,africa4 ,pseudobrookite4 ,fe7,ti,o71 ferric orthotitanate4 ,ti,o #dd-ec4 ,orthorhombic4 ,g #dci-dih4 ,h #f4 ,dark brown to black4 ,norway2 ,france4 ,pyrochlore4 ,a columbate of ,ca and ,e1 with ,th1 ,fe1 ,ti1 ,f1 etc4 ,e,o #ah2 ,ti,o #e-ad4 ,cubic4 ,g #db-dcf4 ,h #e-e4 ,dark brown4 ,scandinavia2 the ,urals2 ,tasmania1 etc4 ,pyrophanite4 ,mn,ti,o1 with traces of ,si,o4 ,ti,o #ej-ec4 ,rhombohedral2 isomorphous with ,ilmenite4 ,g #decg4 ,h #e4 ,deep blood-red2 translucent2 lustrous4 ,pajsberg1 ,sweden4 ,retzian4 ,hydrated arsenate of ,mn1 ,ca1 ,e4 ,cer ,yttr #h-aa4 ,orthorhombic1 usually in prisms4 ,g #dae4 ,h #d4 ,brown2 pleochroic2 transparent4 ,province of ,nordmarken1 ,sweden4 ,rhabdophane 7,scovillite74 ,hydrated phosphate of ,e1 ,al1 ,fe1 ,mg1 etc41 with ,si,o4 ,cer #ech-eg2 ,yttr #ba-ajj4 ,massive4 ,g #cid-dja4 ,h #c4 ,brown to yellow2 translucent4 ,cornwall2 ,scoville1 ,connecticut1 ,u4,s4,a4 ,rhnite4 7,na1,k1,h7,ca7,fe1,mg77,al1,fe77,si1,ti 7,o4 ,ti,o #ie4 ,anorthic1 isomorphous with ,aenigmatite4 ,g #ce-dc4 ,brown1 with strong pleochroism4 ,rhn ,mountains1 ,saxony4 ,rinkite4 ,a titanosilicate closely allied to ,mosandrite and ,johnstrupite 7q4v47--,na,ca,ce7,ti1,th7,si,o8 ,cer #ba2 ,yttr #jd-ad2 ,ti,o #ac-ad4 ,monoclinic1 very close to ,johnstrupite4 ,g #cdf4 ,h #e4 ,yellow1 pleochroic2 translucent4 ,kangerdluarsuk1 ,greenland4 ,risrite4 ,an yttria columbate1 near ,fergusonite1 but with no ,u and considerable ,ti,o2 ,yttr #cg2 ,cer #bi-dj2 ,ti,o #fe4 ,no data yet determined4 ,isotropic4 ,g #dagi4 ,h #e4 ,yellowish brown4 ,norway4 ,rogersite4 ,hydrated yttria columbate4 ,yttr #fjab4 ,a weathered ,samarskite8 ,amorphous1 mamillary4 ,g #ccac4 ,h #c4 ,white4 ,mitchell ,co41 ,n4 ,carolina4 ,rosenbuschite4 ,titanosilicate of ,ca1 ,zr1 ,na1 ,e1 ,fe1 ,mn1 with ,f4 ,zr,o #ahg-bj2 ,cer #jc-bd4 ,monoclinic1 in spherical aggregates4 ,g #ccj-cca4 ,h #e-f4 ,orange-grey4 ,near ,brevik1 ,sweden4 ,rowlandite4 ,silicate of ,e1 with ,th1 ,ti1 ,fe1 etc4--#b,y,o1 #c,si,o4 ,cer #add2 ,yttr #dgg2 ,th,o #jf4 ,massive4 ,g #deae4 ,h #f4 ,pale dull green4 ,llano ,co41 ,texas4 ,rutile4 ,titanium dioxide2 ,ti,o #ih-ajj ,tetragonal2 habit prismatic4 ,g #dah-dbe4 ,h #f-f4 ,reddish-brown to black4 ,very widely in ,europe and ,america4 ,samarskite4 ,r,r7,cb1,ta7,o1 where ,r ,fe1 ,ca1 ,,uo2 ,r ,e4 ,cer #ab-fd2 ,yttr #dgb-bab2 ,th,o ,zr,o #g4 ,orthorhombic2 usually massive4 ,g #ef-eh4 ,h #e-f4 ,deep velvet black2 opaque4 ,miask2 ,urals2 ,mitchell ,co41 ,n4 ,carolina4 ,schorlomite4 ,a titaniferous ,garnet--#c;,ca,o17,fe1,ti7,o1#c7,si1,ti 7,o4 ,ti,o #abe-bb4 ,cubic2 usually massive4 ,g #cha-chh4 ,h #g-g4 ,black2 transparent in flakes4 ,magnet ,cove1 ,arkansas4 ,senaite4 7,fe1,mn1,pb7,o1,ti,o1 cf4 ,ilmenite4 ,ti,o #di-eb4 ,rhombohedral2 isomorphous with ,ilmenite1 ,geikielite1 etc4 ,g #ec 7to #db when weathered74 ,h #f4 ,black4 ,diamantina1 ,minas ,geraes1 ,brazil4 ,sipylite4 ,columbate of ,e1 ,zr1 ,fe1 ,u1 ,sn1 etc42 near ,fergusonite 7q4v474 ,cubic1 in octahedra4 ,usually granular4 ,g #dhi4 ,h #f4 ,brownish-black2 translucent4 ,amhurst ,co41 ,virginia4 ,steenstrupine4 ,a silicate of ,e1 ,fe1 ,na1 ,th1 ,mn1 ,al1 ,ti1 ,h,o1 etc42 near ,melanocerite4 ,cer #add-cbe2 ,yttr #j-aei2 ,th,o #ba-ga4 ,rhombohedral4 ,g #cch4 ,h #d4 ,brown2 faces dull4 ,kangerdluarsuk1 ,greenland4 ,strverite4 ,fe,o17,nb1,ta7,o1#d,ti,o4 ,ti,o #fi-ga4 ,tetragonal2 angles very close to those of rutile4 ,g #ej4 ,h #f-g4 ,black2 opaque4 ,craveggia1 ,piedmont1 ,italy2 and in ,madagascar4 ,tachyaphaltite4 ,an altered zircon1 containing ,h,o4 ,zr,o #dj-ej4 ,tetragonal2 very close to ,zircon4 ,g #cf4 ,h #e4 ,dark brown4 ,krager1 ,norway4 ,tengerite4 ,hydrated carbonate of ,e1 ,be1 ,ca1 etc42 a weathered ,gadolinite 7q4v474 ,e,o #cib-dgh4 ,amorphous4 ,white2 opaque2 very soft4 ,llano ,co41 ,texas4 ,thalenite4 ,h,e,si,o1 with traces of ,fe and ,al4 ,yttr #ehf-fci4 ,monoclinic4 ,g #dbc4 ,h #f4 ,bright red and yellow1 sterby1 ,sweden4 ,thorianite4 ,mixed ,th,o ,,uo1 with ,e1 ,pb1 ,zr1 ,si1 ,fe1 etc4 ,th,o #gb-gi2 ,cer #a-h4 ,rhombohedral2 pseudocubic4 ,g #hj-ig4 ,h #g4 ,jet black2 bright resinous lustre4 ,gem-gravels of ,ceylon4 ,thorite4 ,th,si,o1 with ,h,o1 ,u1 ,fe1 ,e1 ,ca1 ,al1 etc4 ,th,o #dad-egi2 ,e,o #j-f4 ,tetragonal2 habit prismatic4 ,g #dd-dh2 ,h #d-e4 ,brown to black4 ,various localities in ,scandinavia4 ,thorogummite4 ,,uo1#c,th,o1#c,si,o1#f;,h,o8 ,an altered ,mackintoshite 7q4v478 ,th,o #dad2 ,e,o #fg4 ,usually massive2 sometimes in crystals resembling ,zircon4 ,g #ddc-ded4 ,h #d-d4 ,dull brown2 opaque4 ,llano ,co41 ,texas4 ,thortveitite4 ,e,o1#b,si,o1 with ,fe1 ,al1 ,mn traces2 ,e chiefly ,sc4 ,yttr #ede4 ,orthorhombic1 in radial aggregates4 ,g #cega4 ,h #f-g4 ,greyish green2 translucent4 ,iveland1 ,stersdalen1 ,norway4 ,titanite 7,sphene1 ,grothite74 ,ca,si,ti,o1 with ,fe1 ,mn4 ,ti,o #cd-de 7usually #da74 ,monoclinic2 wedge-shaped4 ,g #cdj-cef4 ,h #e-e4 ,yellow1 green1 or brown2 pleochroism strong2 lustre resinous4 ,widely distributed in ,europe and ,n4 ,america4 ,titanium ,olivine4 7,h1,fe1,mg77,si1,ti7,o2 ,mn and ,f in traces4 ,ti,o #c-ab4 ,orthorhombic4 ,g #cbe-cbg4 ,h #f-g4 ,deep red to yellow2 pleochroic4 ,pfunders1 ,tyrol2 ,zermatt1 ,switzerland4 ,tritomite4 ,a fluo-borosilicate of ,e1 ,th1 ,ca1 with ,zr1 ,na1 ,h,o1 etc4 ,cer #ddb-eib2 ,yttr #jd-df2 ,th,o ,zr,o #j-ajf4 ,rhombohedral2 in crystals resembling regular tetrahedra4 ,g #dae-dbe4 ,h #e4 ,dark brown2 transparent to opaque4 ,langesund ,fiord1 ,norway4 ,tscheffkinite4 ,titano-silicate of ,e1 ,th1 ,fe1 ,ca1 etc4 ,cer #bc-dg2 ,yttr #j-cd2 ,th,o ,zr,o #j-bj2 ,ti,o #af-ba4 ,massive1 amorphous4 ,g #dbf-dee4 ,h #e-e4 ,velvet black4 ,ilmen ,mountains2 ,nelson ,co4 and ,bedford ,co41 ,virginia1 ,u4,s4,a4 ,tysonite4 ,fluoride of ,e1 with ,th1 ,h,o1 ,,co1 etc4 ,cer #fib-gjf2 ,th,o #j-ca4 ,hexagonal2 in thick prisms4 ,g #fab-fad4 ,h #d-e4 ,wax yellow2 transparent to translucent4 ,fahlun and sterby1 ,sweden2 ,pike's ,peak1 ,colorado4 ,uhligite4 ,titanate of ,zr1 ,ca1 ,al2 ,ca7,zr1,ti7,o ,al7,ti1,al7,o8 ,ti,o #dh2 ,zr,o #bb4 ,cubic2 near to ,perovskite 7q4v474 ,h #e-f4 ,black4 ,transparent in flakes4 ,lake ,magad1 ,e4 ,africa4 ,uraninite4 ,oxides of ,u 7#fj-ge71 with ,pb,o1 ,th,o1 ,zr,o1 ,e,o1 ,fe,o1 etc4 ,cer4 #j-bg2 ,yttr #j-ajb2 ,th,o #af-aaa2 ,zr,o #j-ha4 ,cubic1 usually massive2 alters to amorphous pitchblende4 ,g #fd 7massive72 #ig 7crystalline74 ,h #e4 ,black2 transparent in splinters4 ,norway2 ,bohemia2 ,saxony2 ,cornwall2 ,carolina1 etc4 ,vietinghofite4 ,a hydrated ferruginous samarskite 7q4v474 ,e,o #hb2 ,zr,o #aj4 ,amorphous4 ,g #eec4 ,h #e-f4 ,dull black2 opaque4 ,lake ,baikal1 ,siberia4 ,warwickite4 #f,mg,o1,fe,o1#b,ti,o1#c;,b,o8 ,ti,o #bce4 ,orthorhombic2 habit prismatic1 elongated4 ,g #cce-ccf4 ,h #c-d4 ,dark brown to black2 pleochroic4 ,double refraction strong1 ve4 ,edenville1 ,new ,york ,state4 ,weibyite4 ,carbonate of ,e1 with ,ca1 ,sr1 ,f1 and ,h,o2 allied to ,bastnsite 7q4v474 ,cer #ffif8 ,orthorhombic2 in pyramids resembling those of ,zircon4 ,crystals are small1 and covered with a thin yellow crust2 they are intergrown with ,parisite 7q4v47 ,langesund ,fiord1 ,norway4 ,wiikite4 ,titano-tantalo-silicate of ,zr1 ,th1 ,e1 ,fe1 ,u1 with ,cb,o1 ,h,o1 etc4 ,cer #be2 ,yttr #gf2 ,sc,o #ab2 ,th,o #ee2 ,zr,o ,ti,o #bcd4 ,perfectly amorphous4 ,g #dhe4 ,h #f4 ,black2 opaque2 infusible4 ,impilaks1 ,lake ,ladoga1 ,finland4 ,whlerite4 ,silicate and columbate of ,ca1 ,zr1 ,na2 ,si,zr,cb,o,f,ca,na8 ,zr,o #aeb-bbg4 ,cer1 traces4 ,monoclinic2 prismatic or tabular habit4 ,g #cda-cdd4 ,h #e-f4 ,light yellow2 pleochroic4 ,langesund ,fiord4 ,xenotime4 ,phosphate of ,e1 with ,th,o1 ,si,o1 ,zr1 etc4 ,cer #j-aa2 ,yttr #eda-fdg2 ,th,o #a-e4 ,tetragonal2 isomorphous with ,zircon8 ,g #dde-def4 ,h #d-e4 ,brown to yellow2 opaque4 ,diamond sands of ,brazil2 ,norway4 ,yttrialite 7,green ,gadolinite74 ,a weathered gadolinite 7q4v47--,e,o1#b,si,o4 ,cer #ff-hb2 ,yttr #dcd-dfe2 ,th,o #ajh-abh4 ,amorphous1 massive4 ,g #df4 ,h #e4 ,green to brown2 translucent4 ,bluffton1 ,llano ,co41 ,texas4 ,yttrocerite4 ,ca,e,f1 #a;,h,o4 ,cer #ic-ahb2 ,yttr #ha-bid4 ,massive1 granular4 ,g #cde4 ,h #d4 ,white to violet blue or brown4 ,various localities in ,scandinavia4 ,yttrocrasite4 7,ca1,pb7,o17,th1,u7,o1#c;,e,o1#af,ti,o1 #f;,h,o4 ,yttr #beg2 ,cer #bi2 ,th,o #hg2 ,ti,o #dig4 ,orthorhombic2 axial ratios unknown4 ,g #dhj4 ,h #e-f4 ,black2 lustrous4 ,burnet ,co4 ,texas4 ,yttrofluorite4 n,ca,f m,,yf in isomorphous mixture8 ,yttr #bj-be2 ,cer #a-b4 ,cubic4 ,g #ced-cef4 ,h #d4 ,closely resembles fluorspar1 except in badness of cleavage4 ,northern ,norway4 ,yttrogarnet4 ,a variety of garnet with ,e and ,zr4 ,yttr #a-fg2 ,zr,o #j-c4 ,cubic 7cf4 ,garnet74 ,dark reddish brown 7cf4 ,garnet74 ,stock1 ,norway2 ,schreiberhau1 ,germany4 ,yttrogummite4 ,,uo1 #c,th,o1 #c,si,o1 #f;,h,o8 ,e,o #fg2 ,th,o #dad4 ,tetragonal2 angles near ,zircon4 ,usually massive4 ,g #ddc-ded4 ,h #d-d4 ,yellowish brown4 ,llano ,co41 ,texas4 ,yttrotantalite4 ,r,r7,cb1,ta7,o #d;,h,o2 ,r ,fe1 ,ca2 ,r ,e2 ,cer #j-bd2 ,yttr #agb-chc4 ,orthorhombic2 isomorphous with ,samarskite 7q4v474 ,g #ee-eh4 ,h #e-f4 ,yellow to black4 ,ytterby1 ,sweden2 ,south ,norway4 ,zircon4 ,zr,si,o1 with ,fe1 ,th1 etc41 in traces4 ,zr,o #faj-gjj4 ,tetragonal2 habit prismatic4 ,g #dfh-dgj4 varying considerably4 ,h #g4 ,colour very variable4 ,widely distributed as a rock mineral1 in sands1 etc4 ,zirkelite4 7,ca1,fe77,zr1,ti1,th7,o1 with ,e1 ,u1 ,mg1 etc4 ,zr,o #dhi-ebi2 ,th,o #j-gc2 ,ti,o #ad-ae2 ,e,o #j-c4 ,cubic2 in twinned octahedra4 ,g #dg4 ,h #e4 ,black2 transparent in thin flakes4 ,jacupiranga1 ,so ,paulo1 ,brazil4 ,,chapter ,,ii ,,the ,,silicates 7a7 ,,silicates ,,of ,,the ,,yttrium ,,and ,,cerium ,,metals ,cerite4--,cerite is a silicate of the cerium metals1 with small amounts of lime1 ferrous oxide and water4 ,hintze gives the formula ,h7,ca1,fe7,ce,si,o1#ae which ,groth interprets as a basic metasilicate 7,ca1,fe7,ce,o,ce7,,oh77,si,o71 i4e4 a basic salt of the acid ,h,si,o1 a polymer of metasilicic acid1 ,h,si,o4 #ae ,the symbol 7,ca1,fe7 here indicates that the iron and calcium occur in variable proportions1 the variation however occurring in such a way that the equivalent of the two taken together is always the same1 i4e4 the iron can replace the calcium1 or vice versa1 atom by atom4 ,the recognition of this possibility of #8,vicarious ,replacement' between similar elements first brought order into the confused field of mineral chemistry1 and allowed a systematic classification of minerals according to chemical composition to be made4 ,iron and calcium1 or1 according to the more convenient nomenclature of the mineralogists1 lime and ferrous oxide1 are here vicarious constituents4 ,the symbol ,ce here stands for elements of the cerium group1 which are never found singly4 ,crystals are not very common1 the mineral usually occurring granular or massive4 ,crystals1 orthorhombic1 holosymmetric2 a 3 b 3 c #jiihh 3 #a 3 #jhabg4 ,usual forms--the ,pinakoids a1 b1 and c #ajj1 #jaj and #jja1 prisms m #aaj and q #acj1 domes u #aja1 t #cja and n #jaa1 and some pyramids hkl4 ,angles1 a m #dd #eh1 u c #ci #h1 n c #ci #f4 ,the crystals usually occur as short prisms4 ,no cleavage4 ,optical constants unknown4 ,in flakes the absorption spectrum of didymium can be observed4 ,the mineral is brittle2 hardness #e to #f on ,mohs' scale2 sp4 gr4 varies a little about #di4 ,fracture splintery2 lustre dull1 resinous4 ,colour brown to red and greyish-red1 streak greyish-white4 ,the mineral is almost opaque4 ,cerite is infusible before the blowpipe4 ,it is attacked readily by sulphuric acid1 less easily by hydrochloric acid1 with which it gives a gelatinous mass4 ,rammelsberg#af found that the silica left behind on treatment of the powdered granular variety with the latter acid contained a variable proportion of bases1 which he obtained and estimated after fusing the siliceous residue with sodium carbonate4 ,from the different proportions of the earths in the part attacked by the acid and that left in the silica1 he remarks1 #8,it would almost appear that ,cerite is a mixture of silicates which are not all attacked with the same ease by hydrochloric acid4' ,apparently without previous knowledge of this observation1 ,welsbach#ag noticed the same thing in #ahhd4 ,he concluded that ordinary granular #8cerite' is a mixture of several minerals1 among which there are at least two which contain rare earths4 ,of these1 one1 the chief constituent of the aggregate1 is probably identical with the crystallised mineral1 and is characterised by the readiness and completeness with which it is attacked by hydrochloric acid4 ,the other does not react1 with hydrochloric1 but is readily attacked by sulphuric acid2 it contains yttria earths1 in addition to the ceria earths4 ,in the extraction of ceria earths from the mineral aggregate1 ,welsbach used hydrochloric acid1 so leaving this second mineral unchanged2 but to avoid loss of the rare earths1 sulphuric acid is more commonly employed for the decomposition4 #af ,pogg4 ,ann41 #ahei1 #ajg1 #fca4 #ag ,monats41 #ahhd1 #e1 #eab4 ,though of great historical interest1 cerite is of very small importance for the extraction of rare earths at the present time1 on account of its very rare occurrence4 ,the mineral seems to be almost entirely confined to the ,bastns quarry near ,ryddarhyttan1 ,sweden1 where it is found with the rare earth silicate allanite 7q4v471 biotite1 hornblende1 bismuth glance1 chalcopyrite1 etc4 ,here it was observed in #agea by ,cronstedt1 who called it ,tungsten 7vide supra1 p4 #a74 ,in #agha ,scheele examined a specimen of ,wallerius's #8,tenn-spat' from ,bipsberg1 ,dalecarlia1 and found ,tungstic ,oxide 7,acid71 ,,wo1 in it4#ah ,after ,scheele's work1 the ,ryddarhyttan mineral was known as ,red ,tungsten1 until ,bergmann 7#aghj7 and d',elhuyar 7#aghd7 showed that the two minerals were chemically distinct4 ,they considered the red variety to be a silicate of iron and calcium1 the rare earths being mistaken for lime4 ,in #ahjd ,klaproth examined it1 and found a new earth2 he called the mineral #8,ochroite1' from its colour4 ,in the same year1 but independently of ,klaproth1 ,berzelius and ,hisinger made the same discovery2 they called the mineral ,cerite and the new metal ,cerium1 in honour of the discovery of the minor planet ,ceres by ,piazzi in #ahja4 #ah ,this mineral1 which ,scheele knew as ,tungstein1 is now called ,scheelite4 ,the analyses of cerite made in the earlier part of the nineteenth century resulted in some confusion4 ,klaproth in #ahjg found #cde per cent4 ,si,o in a specimen 7his ,ochroite72 ,vauquelin in #ahje1 and ,hisinger in #ahaj1 found #agj and #ahj per cent4 respectively4#ai ,hermann#bj called attention to this discrepancy in #ahdc 7and again in #ahfa71 and declared that the two could not be the same4 ,for ,klaproth's mineral he proposed to revive the name ,ochroite1 whilst from his own analyses he proposed for the cerite of ,berzelius the name ,lanthanocerite1 having found carbon dioxide and lanthanum1 with much less cerium1 in the latter4#ba ,in #ahfa ,kenngott partly explained these results by showing that the sample of cerite which ,hermann had analysed contained ,lanthanite#bb2 but the extraordinarily high percentage of silica obtained by ,klaproth remained unexplained4 ,it may have been due to impurities of high silica content in the specimen he examined4 #ai ,vide ,hintze1 ,handbuch der ,mineralogie1 ,leipzig1 #ahig1 ii41 #acbi4 #bj ,hermann1 ,j4 pr4 ,chem4 #ahdc1 #cj1 #aid1 and #ahfa1 #hb1 #djf4 #ba ,the announcement of the discovery of ,lanthanum by ,mosander was made in #ahci4 #bb ,lanthanite 7see list7 is an hydrated carbonate1 ,r,o1#c;,,co1#i;,h,o1 where ,r cerium metals1 chiefly ,lanthanum4 ,cerite contains from #eid to #gah per cent4 of rare earths 7oxides71 the amount and nature of which vary with the precise locality4 ,the oxides consist chiefly of ceria1 lanthana1 and didymia 7praseodymia and neodymia71 the complexity of the so-called ceria having been shown by ,mosander in the case of ceria separated from gadolinite as well as from cerite2 but yttria earths are also found to a small extent in the mineral4 ,it is remarkable that neither thorium nor uranium has been found in cerite1 which is thus practically unique among the rare earth minerals4 ,this anomaly becomes even more marked in view of the very high percentage of inert gases found by ,tschernik#bc in a related mineral from ,batoum4 ,this is a very complex mineral in which the basic part is represented by rare earths1 chiefly ceria earths 7#ejh per cent47 with water 7#cd per cent471 and oxides of iron1 calcium and copper 7#fh per cent472 the acidic oxides being silica 7#ff per cent471 zirconia 7#aaf per cent471 and titanium dioxide 7#adg per cent471 with phosphorus pentoxide 7#cb per cent471 and sulphuric anhydride 7#ag per cent474 ,traces of thoria are present1 but no uranium2 very considerable quantities 7up to #a per cent487 of helium were found4 #bc ,g4 ,tschernik1 ,j4 ,russ4 ,phys4 ,chem4 ,soc4 #ahif1 #bh1 #cde2 #ahig1 #bi1 #bia4 ,abstracts in ,zeitsch4 ,kryst4 ,min4 #ahii1 #ca1 #eac and #ead4 ,it is somewhat heavier than cerite 7sp4 gr4 #ejh71 but otherwise resembles it closely4 ,gadolinite 7,ytterbite74--,gadolinite is a silicate of iron1 beryllium1 and the yttria earths1 of the formula #b;,be,o1,fe,o1,y,o1#b,si,o1 which may be written ,fe,be,y,si,o4 ,according to ,groth1 it is a basic orthosilicate1 ,be,fe7,,yo77,si,o71 derived from the acid ,h,si,o4 ,the beryllium content varies considerably1 and some authors recognise two varieties of the mineral1 one rich1 and one poor in beryllium2 but ,scheerer pointed out in #ahdj that iron and beryllium are probably vicarious constituents4 ,analysis gives silica #bah to #bec per cent42 yttria earths #bb to #dg per cent42 ceria earths #e to #ca per cent4 ,in a variety from ,ytterby1 the rare earth ,scandia was first found1 forming up to #jjb per cent4 of the mineral4 ,small quantities of thoria1 ,th,o may be present1 and traces of helium were found by ,ramsay1 ,collie1 and ,travers4 ,according to ,strutt it contains also uranium and radium4 ,like cerite1 it does not often occur crystalline1 being usually found in amorphous masses4 ,the crystals are monoclinic2 a 3 b 3 c #jfbgc 3 #a 3 #acbae2 #hi #bf4 ,common forms are--,ortho-1 clino-1 and basal pinakoids1 a #ajj1 b #jaj1 and c #jja1 hemi-prisms m #aaj1 v #abj1 clino-prisms w #jab1 q #jaa1 and many others2 and various hemi-pyramids hkl and hkl4 ,angles a m #cb #f1 c q #eb #ec1 c 7#aja7 #fd #i4 ,crystals commonly prismatic1 terminated by c4 ,faces rough and coarse2 lustre vitreous to greasy1 seen only on freshly-broken surfaces4 ,brittle4 ,no cleavage4 ,fracture conchoidal to splintery4 ,hardness #f-g2 sp4 gr4 #dj-de4 ,colour black1 greenish- and brownish-black2 green and transparent in flakes4 ,the crystalline variety has strong positive birefringence1 with the plane of the optic axes parallel to 7b71 the plane of symmetry2 the amorphous variety is of course isotropic4 ,the brown variety shows very distinct pleochroism1 i4e4 the colour as seen by transmitted light varies with the direction in which the light traverses the crystal2 the green kinds have much weaker pleochroism4 ,gadolinite is of common occurrence in the pegmatite veins of the ,scandinavian granite4 ,it was first found in a felspar quarry on the island of ,ytterby1 near ,stockholm1 by a ,lieutenant ,arrhenius#bd2 it is also found1 together with a large number of other rare earth minerals1 at ,fahlun4 ,it occurs in ,norway on the islands of ,hitter and ,mal1 and in ,germany in the ,riesengebirge and the ,harz4 ,probably the largest deposit is that in ,texas1 at ,barringer ,hill1 near ,bluffton1 on the west bank of the ,colorado ,river1 ,llano ,county1 now owned and worked by the ,nernst ,light ,company of ,pittsburg2 in #aijd a mass of very pure gadolinite weighing #bjj lb4 was found here4#be #bd ,vide ,geijer1 ,crell's ,chemische ,annalen1 #aghh1 #a1 #bbi4 #be ,see ,u4,s4 ,geol4 ,survey 7,minerals71 #aijd1 #abac4 ,in the same place a decomposition product of gadolinite was discovered by ,hidden and ,mackintosh in #ahhi4 ,they named it ,yttrialite or ,green ,gadolinite4 ,it contains no beryllium1 and twice as much silica as the parent mineral1 and approximates to the formula ,r,o1#b,si,o1 where ,r,o is chiefly yttria oxides2 it is thus similar in composition to the newly found scandium silicate1 ,thortveitite 7q4v474 ,it is amorphous and massive2 and is often found in continuous growth with gadolinite4 ,pieces up to #aj lb4 in weight have been obtained4 ,as stated above1 ,gadolinite was discovered by ,arrhenius in #aghh4 ,geijer examined it in the same year1 and described it as a black zeolite4 ,in #agid it was analysed by ,gadolin1 who declared it to be a silicate of iron1 aluminium1 and a new element which he called ,ytterbium4 ,in #agig ,ekeberg examined it1 and confirmed the discovery4 ,he proposed the name ,gadolinite for the mineral1 and ,yttria for the new earth2 these names were accepted by ,klaproth1 who examined it with ,vauquelin in #ahjj1 and by the ,french crystallographer ,hay4 ,in #ahjb ,ekeberg showed that the oxide originally taken for alumina was in reality beryllia2 in #ahaf ,berzelius showed that ceria was present with the yttria4#bf ,about #ahch ,mosander began his classical work on the earths in gadolinite4 ,in that year he announced the separation of ,lanthana1#bg and in #ahdb that of ,didymia1 which he had actually discovered eighteen months earlier4 ,in the latter year he announced#bh the separation of erbia and terbia4 ,in #ahdb also ,scheerer#bi declared that the yttria from gadolinite was a mixture of earths1 from its different behaviour on heating in closed and open vessels2 but when ,mosander announced the discovery of didymia 7the announcement appears to have been hastened indeed by ,scheerer's observation7 it was agreed that the colouration observed was probably due to that earth4 ,the further history of these earths must be continued elsewhere 7vide p4 #aaa74 #bf ,schweigg4 ,j41 #ahaf1 #af1 #dje4 #bg ,berzelius 7a letter to ,pelouze71 ,pogg4 ,ann41 #ahci1 #df1 #fdh4 #bh ,berz4 ,jahres41 #bc1 #ade2 #bd1 #aje4 #bi ,pogg4 ,ann41 #ahdb1 #ef1 #dhc4 ,the behaviour of gadolinite on heating is of great interest4 ,when heated uniformly1 in closed or open vessels1 the mineral suddenly glows very strongly at a definite temperature 7according to ,hofmann and ,zerban#cj at #dcj;,c471 with considerable alteration in properties4 ,the amorphous variety exhibits the phenomenon much more markedly than the crystalline form4 ,the change in the two cases is entirely distinct1 the only effect in common being that both varieties are rendered insoluble in acids after the glowing4 ,the amorphous variety1 in the act of glowing1 changes to the crystalline form4 #cj ,ber41 #aijc1 #cf1 #cjie4 ,this phenomenon of phosphorescence1 or glowing1 on heating1 with a change in properties1 was first observed by ,berzelius in #ahaf4 ,he found that the oxides of many metals1 e4g4 chromium1 tantalum1 and rhodium1 became denser and insoluble in acids after being heated4 ,later in the same year he observed the glowing1 with a similar change in properties1 in the case of a gadolinite from ,fahlun4#ca ,apparently without knowledge of this observation1 ,wollaston published a similar account of the glowing of a gadolinite in #ahbe4 ,in #ahdj ,scheerer noted an almost identical change in the case of the mineral allanite 7q4v474 ,scheerer made a careful study of the phenomena in the cases of allanite and gadolinite4#cb ,in each case he found that the variety of lower specific gravity showed1 on heating1 a very strong phosphorescence1 accompanied by change of colour and optical properties1 and a marked increase of specific gravity4 ,gadolinite suffered no appreciable loss of weight1 but allanite had lost a little water after the change4 ,careful measurement of the specific gravity before and after the change showed1 in the case of two varieties of gadolinite and one of allanite1 that the volume had decreased in the ratio #a 3 #jid4 ,scheerer assumed that this ratio was constant for all such cases1 and advanced a general explanation4 ,we know now that numerous cases of similar phenomena occur1 in which the change of volume is quite different2 but ,scheerer's explanation is so ingenious1 and so foreshadows some modern theories1 that it is given here in full4 #ca ,schweigg4 ,j41 #ahaf1 #af1 #dje4 #cb ,pogg4 ,ann41 #ahdj1 #ea1 #dic4 ,he ascribes the alteration to #8interatomic change1 involving change of relative position of atoms and decrease of interatomic distances4' 7,scheerer and the chemists of that period understood by atoms the ultimate particles of a body1 making no distinction between elements and compounds2 in this case he meant by atoms what we mean by molecules1 and the word #8molecule' has therefore been substituted for #8atom' in what follows47 ,the change is simply one of closer packing of the molecules1 which take up a more stable position with liberation of energy as heat and light4 ,he imagines his molecules as uniform spheres arranged in horizontal layers1 as shown in ,fig4 #a4 ,in placing one layer vertically over another there are three possible arrangements1 of which only two concern us4 ,in the arrangement for closest packing1 ,b1 say1 a molecule of any one layer touches three molecules in each of the layers above and below1 which with the six it touches in its own layer make twelve altogether4 ,in the next closest arrangement1 ,a1 say1 a molecule of any one layer touches only two molecules in each of the layers above and below it1 so that one molecule is in contact with ten others altogether4 ,illustration3 ,,fig4 #a ,now it can be shown that the volumes of equal numbers of molecules in the arrangements ,a and ,b will be to one another as the height1 ,h1 of an equilateral triangle1 to the height1 h1 of a regular tetrahedron whose edges are equal to the sides of the triangle1 a length ,r 7which will be equal to the diameter of a molecule74 ,then ,h ,r#c1 h ,r4 ,then vol4 in arrangement ,a 3 vol4 in arr4 ,b ,h 3 h i4e4 #c_/b 3 #a 3 #jidc4 ,that is1 the volume changes in the ratio #a to #jidc1 the amorphous variety of gadolinite consisting of molecules in arrangement ,a1 which go over to the closer packed arrangement ,b in the change to the crystalline form4 ,more extended work has shown that this ingenious and interesting explanation is not of general application4 ,thus ,h4 ,rose#cc found that samarskite 7q4v47 exhibited the phenomenon of glowing1 but that the specific gravity was actually less after the change than it was before1 i4e4 there was an increase of volume4 ,damour observed glowing in the case of zircon from ,ceylon 7q4v47 with increase of density1 the volume change being from #a to #jibb1 i4e4 even greater than for gadolinite4 ,again1 ,hauser#cd observed in the case of his new rare earth mineral risrite a sudden change at a red heat1 the mineral losing water1 becoming very brittle1 and increasing very considerably in specific gravity 7the volume changing from #a to #jij approximately71 but without glowing4 ,ramsay and ,travers#ce found that fergusonite 7q4v47 glowed strongly when heated to #ejj-fjj1 with decrease of specific gravity 7#efb before to #ecg after71 evolution of all its helium1 and very considerable evolution of heat2 they suggested that helium was present in combination1 in an endothermic compound decomposed by heat1 but in view of the properties of helium1 this hypothesis seems hardly tenable4 #cc ,j4 pr4 ,chem4 #aheh1 #gc1 #cia4 #cd ,ber4 #aijg1 #dj1 #caah4 #ce ,zeitsch4 physikal4 ,chem4 #ahih1 #be1 #efh4 ,it appears unlikely that any one explanation can cover all these interesting facts2 there are in each case peculiar factors to be taken into account4 ,in #ahda1 ,regnault1#cf considering the case of the oxides observed by ,berzelius1 inferred that the development of light and heat denoted that the bodies possessed a lower specific heat after the change than before4 ,the experimental difficulties encountered in attempting to dry the oxides prevented him from confirming this view4 ,he measured the specific heats of the minerals calcite and aragonite 7,ca,c,o71 and of the two allotropic modifications of phosphorus1 but could observe no appreciable differences4 ,h4 ,rose 7vide supra7 showed by experiment that considerable heat was evolved on the glowing of gadolinite1 with a decrease of about one-fourteenth in the specific heat4 ,in the case of samarskite there was1 however1 no appreciable evolution of heat1 nor could he determine any difference in the specific heats before and after glowing4 #cf ,pogg4 ,ann4 #ahda1 #ec1 #bdi4 ,probably the only inference that can be safely drawn is that in most cases the change is due to some molecular re-arrangement4 ,the evolution of water1 helium1 etc41 in some cases1 may possibly be due to intramolecular change1 but on the one hand the current view at present is that the helium is mechanically held in radio-active minerals1 and on the other hand it is not known that the water evolved is water of constitution2 in an intermolecular change at fairly high temperature1 these might be evolved without disruption of the true mineral molecules4 ,the question of the energy involved1 and consequently of the specific heats1 appears to depend on factors peculiar to each case1 of which at present no accurate conception can be formed2 and the change in specific gravity is probably bound up with these4 ,the loss of solubility in acids is a factor not always connected with glowing1 as it is frequently observed in the laboratory after ignition of compounds1 but here again no adequate explanation is forthcoming4 ,the possibility of chemical change in one or two cases1 however1 must not be ignored4 ,thus ammonium magnesium phosphate1 ,,nh,mg,p,o1 on heating glows1 and is converted to magnesium pyrophosphate1 according to the equation3 #b,,nh,mg,p,o ,mg,p,o ,h,o #b,,nh ,a case possibly analogous to this is that of the mineral sipylite 7q4v471 ,r,cb,o1 with #8basic water' 7i4e4 ,r partially replaced by ,h74 ,before the blowpipe this decrepitates with loss of water1 and glows brilliantly4 ,the specific gravity after the change does not appear to have been determined4 ,mallet explains the glow as due to a change to the pyrocolumbate4 ,similar explanations may possibly hold in the cases of allanite and risrite1 but it must be remembered that we are really ignorant of the part played by the water in these minerals4 ,allanite4--,allanite1 or ,orthite1 as it is often called1 is a mineral of the epidote family1 containing rare earths4 ,the general formula for ,epidote is ,h,o1#d,r,o1#c,r,o1#f,si,o1 where ,r is a divalent and ,r a trivalent metal1 or vicarious series of metals4 ,in the case of ,allanite1 ,r 7,fe1,ca71 ,r 7,al1,fe1,e71 where ,e stands for metals of the cerium and yttrium groups 7,engstrm's formula74 ,groth formulates it as a basic salt1 ,r7,,oh7,r,si,o1 of the acid ,h,si,o 7 #c;,h,si,o74 ,crystals are fairly common1 but the mineral usually occurs massive or in rounded grains4 ,crystals--,monoclinic1 holosymmetric2 a 3 b 3 c #aeeji 3 #a 3 #agfia1 #fd #ei4 ,common forms--,ortho- and basal pinakoids a #ajj and c #jja2 m #aaj and other prisms1 e #aja and other hemi-ortho-prisms1 o #jaa1 d #aaa and other hemi-pyramids4 ,angles1 7#ajj7 7#aaj7 #ed #cd2 7#jja7 7#aja7 #fc #bd2 7#jja7 7#jaa7 #eh #c4 ,tabular1 parallel to a1 or long and slender by elongation parallel to axis b4 ,birefringence weak1 variable4 ,refraction strong4 ,colour brown to brownish-black2 almost opaque4 ,in flakes very strongly pleochroic1 the colours for light parallel to the three vibration directions c1 b and a being brownish-yellow1 reddish-brown1 and greenish-brown respectively4 ,brittle4 ,hardness #e-f2 sp4 gr4 #ce-db4 ,on heating1 allanite becomes amorphous and isotropic with increase of specific gravity 7cf4 ,gadolinite74 ,before the blowpipe it loses water1 and melts to a black magnetic glass1 many varieties phosphorescing strongly 7vide supra74 ,with hydrochloric acid it gelatinises1 unless previously heated strongly1 in which case it is not attacked4 ,analyses show that the rare earth content varies considerably 7vicariously as regards ferric iron and aluminium71 ceria earths varying from #cf to #eaa per cent4 and yttria earths from traces up to #dg per cent4#cg ,thoria is usually present1 #j to #ce per cent4 ,in #aiji ,fromme#ch found small quantities of beryllia in the mineral1 and in #aiaa ,meyer#ci found amounts of scandium oxide up to #a per cent4 ,it contains traces of uranium1 and is weakly radioactive4 ,ramsay1 ,collie and ,travers found no helium 7#ahie71 but in #aije ,strutt found radium in it1 so that the presence of helium seems a priori probable4 #cg ,vide ,schilling1 pp4 #gj-ge for analyses of this mineral4 #ch ,fromme1 ,tsch4 ,min4 ,mitt4 #aiji1 #bh4 #ci ,meyer1 ,sitzungsber4 knigl4 ,akad4 ,wiss4 ,berlin1 #aiaa1 #cgi4 ,many varieties of the mineral are known1 differing in habit1 colour1 water content1 specific gravity1 etc41 and the percentage composition varies very much by reason of vicarious replacement of the bases4 ,goldschmidt#dj has found #8,epidote-orthites' which are isomorphous mixtures of orthite with an iron epidote2 he concludes that most orthites are probably similar solid solutions1 and in this way accounts to a large extent for the varying composition4 #dj ,centr4 ,min4 #aiaa1 #d4 ,allanite is of very wide distribution1 though it is not often found in large quantities4 ,the usual occurrence in pegmatitic veins in granites1 syenites and other acid plutonic rocks has been often noted1 e4g4 in many parts of ,sweden and ,norway4 ,it is found also in the extinct crater now forming the ,laacher ,see1 near ,coblenz1 ,germany1 and at ,impilaks1 near ,lake ,ladoga1 on the border of ,finland2 a mass of the pure mineral weighing #cjj lb4 was recently discovered at ,barringer ,hill1 7cf4 under ,gadolinite71 and it occurs in large quantities in ,amherst ,co41 ,virginia4 ,it is an accessory constituent of many acid volcanic and hypabyssal rocks1 and has been found also in limestone1 and in magnetic iron ores4 ,on account of its exceedingly wide distribution1 and the variations in appearance and composition1 it has been repeatedly described under various names1 varieties being constantly mistaken for new mineral species4 ,its history is rather curious4#da ,in #ahjf the ,danish mineralogist ,giesecke made a protracted voyage to ,greenland1 collecting minerals and rocks2 he remained there until #ahac4 ,in #ahjh he sent off his first collection by ship to ,copenhagen2 on the voyage the ship was taken by an ,english privateer1 and the cargo landed and sold at ,leith4 ,the minerals were bought by ,allan1 a ,scotch mineralogist1 who recognised1 that they were from ,greenland by the presence of cryolite1 at that time only known to occur in ,greenland4 ,he mistook the mineral subsequently named after him for gadolinite1 and sent it to ,thomson for analysis4#db ,thomson recognised it as a new mineral1 and named it ,allanite 7#ahaj74 ,in #ahae ,hisinger described a mineral from ,ryddarhyttan1 ,sweden1 which he called ,cerin2 ,leonhard 7#ahba7 and ,hauy 7#ahbb7 showed that this was identical with ,allanite4 ,in #ahah ,berzelius described two varieties of a mineral from ,finbo1 near ,fahlun1 ,sweden1 which he called ,orthite1 and ,pyrorthite2 these were eventually shown by ,scheerer 7#ahdd7 to be varieties of ,allanite4 ,in #ahbd the ,french mineralogist ,lvy described a mineral from ,arendal1 ,norway1 which he named ,bucklandite1 in honour of the ,english naturalist2 in #ahbe this was identified with a #8black zeolite' from the ,laacher ,see by ,g4 ,rose1 and in #ahbh both were shown by ,hermann to have the same composition as orthite or allanite4 ,the list might be extended at will2 the ,tautolite of ,kokscharow 7#ahdg71 the ,bodenite of ,breithaupt 7#ahdd71 the ,muromontite of ,kemdt 7#ahdh71 and the ,vasite of ,bahr 7#ahfc7 have all been shown to be varieties of the same bewildering mineral4 #da ,vide ,schilling1 pp4 #ge-gf1 where full references are given4 #db ,see ,kobell's ,geschichte der ,mineralogie1 #ahfd1 p4 #fgi4 ,hellandite4--,hellandite#dc is a mixed silicate of rare earths with lime1 magnesia1 alumina1 ferric and manganic oxides1 with considerable quantities of water4 ,the formula approximates to #c;,h,o1#b,r,o1#c,r,o1#d,si,o1 where ,r 7,ca1,mg1,th_/#b7--,thorium being able to replace two atoms of calcium or magnesium--and ,r 7,al1,fe1,mn and rare earth metals74 ,this may be written as a basic orthosilicate1 ,r,r7,,oh77,si,o71 a basic salt of the acid ,h,si,o 7 #d;,h,si,o74 ,this composition puts it in the class containing topaz and some rarer silicates4 #dc ,brgger1 ,zeitsch4 ,kryst4 ,min4 #aijf1 #db1 #dag4 ,the mineral is crystalline1 the crystals being well developed1 but often dull and opaque by alteration 7hydration74 ,crystal system--,monoclinic1 holosymmetric1 a 3 b 3 c #bjfdf 3 #a 3 #bejg4 #aji #de4 ,habit usually prismatic1 with #ajj1 #jaj1 and several prisms hko1 terminated by various pyramid forms4 ,angles 7#ajj7 7#jja7 #gj #cb2 7#ajj7 7#aaj7 #fb #bb2 7#jaj7 7#aaj7 #bg #ad2 7#aaj7 7#aaj7 #abe #j4 ,twinned on 7#jja71 twin plane 7#jja71 forming knee-shaped twins4 ,hardness varies from #e in the least altered to #a in the most altered specimens2 sp4 gr4 #cgj in least altered specimens1 decreasing with hydration4 ,colour of fresh crystals1 reddish-brown2 on alteration they become brownish-black1 yellow1 or even white4 ,the mineral dissolves easily in hydrochloric acid1 with evolution of chlorine2 it is less soluble in nitric and sulphuric acids4 ,it readily fuses to a yellow mass4 ,it was first discovered by ,brgger at ,lindvikskollan1 in #aijc1 and later1 in larger quantities1 at ,krager in ,norway4 ,it occurs in pegmatite veins in granite4 ,thalnite4#dd--;,a silicate of yttria earths with water and small quantities of alumina1 ferric oxide1 carbon dioxide and alkalies4 ,the ratio of rare earths to silica gives the formula ,r,o1#b,si,o1 or ,r,si,o2 if the water be included1 the formula becomes ,h,r,si,o4 ,the presence of both water and carbon dioxide indicates1 however1 that the mineral has been somewhat altered1 and the simpler formula ,r,si,o1 7cf4 ,thortveitite1 below7 probably expresses the composition of the original mineral4 ,it contains considerable quantities of nitrogen and helium1 though uranium and thorium appear to be absent4 #dd ,benedicts1 ,abstract in ,zeitsch4 ,kryst4 ,min4 #aijj1 #cb1 #fad4 ,monoclinic2 a 3 b 3 c #aaed 3 #a 3 #jfjb4 #hj #ab4 ,common forms are the pinakoids #ajj and #jaj1 hemi-prism #aaj1 hemi-pyramids #aaa and #aaa1 and others1 and the hemi-dome #jba4 ,angles1 7#ajj7 7#jaj7 #ia #j2 7#ajj7 7#aaj7 #dh #i2 7#ajj7 3 7#aaa7 #ei #d4 ,double refraction weak4 ,no cleavage4 ,brittle4 ,hardness #f4 ,colour1 bright flesh-red2 translucent1 with greasy lustre2 sp4 gr4 #dbbg1 increasing to #dbi after ignition4 ,a yellow variety has sp4 gr4 #daa-daf1 and is transparent4 ,the #8average atomic weight' of the rare earth metals is #ii1 from which it appears that these consist chiefly of yttrium1 with a smaller quantity of the metals of higher atomic weight4 ,it was discovered in #ahih by ,benedicts1 accompanying fluocerite 7q4v47 in a quartz quarry at ,oesterby in ,dalekarlia4 ,thortveitite4#de--;,a silicate of yttria earths1 chiefly scandia1 of the formula ,r,o1#b,si,o4 ,scandia forms about #cg per cent4 of the whole 7,r4 ,j4 ,meyer72 yttria with small quantities of the other yttria earths forms the bulk of the remainder of the bases1 the ceria group being almost completely absent4 ,ferric oxide 7with traces of manganic oxide and alumina7 forms about #c per cent4 ,thorium is present only in traces1 and radioactivity is barely perceptible4 #de ,j4 ,schetelig1 ,centr4 ,min4 #aiaa1 #gba4 ,thortveitite is the first mineral to be discovered in which the content of scandia is greater than #b per cent42 in #aijh ,crookes#df examined a very large number of yttria minerals for scandia1 and finally chose for extraction of the earth ,wiikite 7q4v47 which has a scandia content of #ab per cent4#dg #df ,phil4 ,trans4 #aijh1 ,a1 #bji1 #ae4 #dg ,according to ,eberhard1 some varieties of ,wiikite have a much lower scandia content4 ,thortveitite is orthorhombic2 a 3 b 3 c #jgdef 3 #a 3 #adiab2 commonly combinations of pyramids o #aaa and s #baa with prism m #aaj1 in radial aggregates of crystals elongated parallel to the c axis4 ,cleavage parallel to m1 fair4 ,twin plane m 7#aaj71 twinning very common4 ,refraction strong2 birefringence strong1 negative4 ,acute bisectrix perpendicular to 7#jja71 plane of the optic axes 7#jaj74 ,hardness1 #f-g2 sp4 gr4 #cega4 ,extremely brittle2 lustre brilliant1 vitreous to adamantine4 ,colour1 greyish-green1 white to reddish-grey on alteration2 in transmitted light yellowish-green1 after ignition1 reddish2 the change being probably due to presence of oxides of iron4 ,it is fusible with difficulty1 and only partially attacked by hydrochloric acid4 ,it was found by ,thortveit1 in #aiaj1 in a pegmatite vein in granite1 at ,iveland1 ,stersdalen1 ,s4 ,norway1 accompanied by euxenite1 monazite1 beryl1 and the usual vein-materials 7quartz1 felspar1 etc474 ,it was analysed and recognised as a new mineral by ,schetelig 7loc4 cit474 99 99 99 99 99 ,the following minerals1 of which particulars will be found in the alphabetical list1 also belong to this class3 ,bagrationite1 ,bodenite1 and ,muromontite1 varieties of allanite with differences in composition and physical properties4 ,yttrialite1 a weathered variety of gadolinite4 ,elpidite1 ,erdmannite and ,cainosite1 more complex silicates4 ,rowlandite1 a comparatively simple silicate of the yttrium metals4 ,yttrogarnet1 a variety of garnet containing yttrium metals4 7b7 ,,silicates ,,of ,,thorium ,,and ,,zirconium ,thorite4--,thorite and its variety ,orangite are somewhat altered forms of a pure silicate of thorium1 ,th,si,o1 containing also small quantities of water1 usually uranium1 and often rare earths1 with iron1 lead1 calcium1 and aluminium4 ,orangite differs from thorite in its beautiful orange colour and greater specific gravity4 ,both varieties are radio-active4 ,when unaltered1 the crystals are tetragonal and uniaxial1 the pure mineral ,th,si,o being isomorphous with zircon1 ,zr,si,o 7q4v474 ,by alteration they become isotropic4 ,crystals are tetragonal1 holosymmetric2 c #jfdjb2 p p #ef #dj4 ,common forms are the prism m #aaj with the pyramids p #aaa and z #caa4 ,hardness #d-e2 sp4 gr4 #dd to #dh for thorite1 #eb to #ed for orangite4 ,thorite contains from #ad to #ca per cent4 of rare earths4 ,according to ,nilson and ,blomstrand1 the uranium is present as uranium dioxide1 ,,uo replacing thoria1 ,th,o1 but ,dunstan and ,blake state that the two oxides are isomorphous 7see under ,thorianite1 p4 #gd71 and so they might be expected to be vicarious4 ,thorite was discovered by ,esmark in #ahbh1 and first analysed by ,berzelius1#dh who announced the discovery of a new earth in it in #ahbi4 ,the name ,thorite is from ,thor1 the god of ,scandinavian mythology4 #dh ,pogg4 ,ann41 #ahbi1 #af1 #che4 ,thorite is a member of a peculiarly interesting series of isomorphous minerals1 which includes ,cassiterite 7,sn,o71 ,rutile 7,ti,o71 ,zircon 7,zr,si,o71 and most probably the allied silicate ,naegite1 and the rare earth phosphate ,xenotime 7q4v471 which are very similar in forms and angles4 ,the oxide ,ti,o is itself trimorphous1 being known in the three crystallographically different forms1 ,rutile1 ,anatase1 and ,brookite 7q4v474 ,on account of the isomorphism of cassiterite and rutile with the two silicates1 it has been suggested that the oxide formul be doubled and written ,sn7,sn,o7 and ,ti7,ti,o7 respectively1#di to show the analogy with ,th7,si,o7 and ,zr7,si,o74 ,consideration of the molecular volumes 7obtained by dividing molecular weight by specific gravity1 i4e4 multiplying by specific volume7 lends a certain amount of support to this view4 ,it has often been observed that isomorphous compounds1 and many compounds which occur in parallel growth to one another1 have nearly equal molecular volumes2 there are1 however1 many exceptions4 ,taking molecular volumes for the series under consideration1 we have1 using approximate numbers only-- ,mol4 ,wt4 ,sp4 ,gr4 ,mol4 ,vol4 ,cassiterite1 ,sn,o #aea #fi #bb ,rutile1 ,ti,o #hj #db #ai ,zircon1 ,zr,si,o #ahb #dg #ci ,thorite1 ,th,si,o #cbe #ed 7,orangite7 #fj ,xenotime1 ,,xpo #ahd #de #da #di ,this isomorphous series has recently been extended by ,zambonini1 and also by ,schaller1 by the inclusion of minerals containing ,columbium and ,tantalum2 see under ,ilmenorutile and ,strverite1 end of ,ch4 ,,iv41 p4 #ga4 ,it will be seen that if the numbers for cassiterite and rutile be doubled1 four out of the five show very fair approximation to the constant value #dj4 ,the number #fj for thorite is quite irreconcilable with the values obtained from the other members2 of course pure silicate of thorium1 ,th,si,o1 is not known as a mineral1 but it is most unlikely that the relatively small amount of impurity in the densest specimens of orangite should have depressed the specific gravity by over two units1 as would be required if the molecular volume of thorite were to show even the most approximate semblance of agreement with the others4 ,it cannot be too often remarked1 however1 that very little indeed is known of the molecular formulas of minerals1 and that very little reliance can be placed on such figures as the above4 ,on the contrary1 it is hardly conceivable that amphoteric oxides like those of tin and titanium1 occurring in the form of heavy crystalline minerals1 should have molecular formul only double the empirical formul4 ,where agreements of the kind do occur1 they must be taken as indicating approximately equal degrees of molecular complexity in the minerals concerned1 rather than as affording any real insight into the molecular condition4 ,zircon4--,zircon is a silicate of zirconium1 ,zr,si,o1 with small quantities of other elements4 ,most varieties contain ferric oxide and thoria2 more rarely small proportions of the yttria earths may be present4 ,all varieties contain traces of a large number of the common metals4 ,traces of radium are usually present1 with helium and neon1#ej and the mineral is strongly radioactive4 #ej ,strutt1 ,nature1 #aijf1 #ajb4 ,system tetragonal1 holosymmetric sub-class4 c #jfdjd2 7#jja7 7#aja7 #cb #ch4 ,usual forms--,prisms a #ajj and m #aaj2 pyramids e #aja1 p #aaa1 u #bba and x #caa1 etc4 ,the basal pinakoid c #jja is rare4 ,the usual combination is one or both of the prisms a1 m1 with one or two pyramids4 ,twinning is rare1 the twin plane being e 7#aja71 giving knee-shaped twins similar to those so characteristic of cassiterite and rutile4 ,cleavage m imperfect1 p bad4 ,brittle2 conchoidal fracture4 ,hardness #g2 sp4 gr4 usually #dfh-dgj1 but varying from #db to #dhf4 ,adamantine lustre4 ,clear and colourless to yellow-1 red- or greenish-brown4 ,transparent to opaque4 ,refraction and double refraction strong1 double refraction positive 7 #aibd1 #aifh1 for sodium light72 on heating it becomes biaxial1 and occasionally is found biaxial in nature4 ,by alteration it becomes isotropic4 ,it is infusible before the blowpipe1 but loses its colour2 some varieties glow and increase in density 7see p4 #ch74 ,in some varieties also the colour changes or disappears rapidly on exposure to sunlight1 and is often restored on keeping in the dark4 ,these phenomena of colour change have been attributed variously to alteration in the state of oxidation of the iron present1 and to the presence of organic matter4 ,it seems probable that either cause or even both may be at the root of the change in particular cases4 ,on account of the hardness1 unalterability1 and strong refraction and double refraction1 good crystals of zircon are used as gems4 ,the two gem varieties1 ,hyacinth and ,jargon1 are found chiefly in the gem gravels of ,ceylon4 ,it was in a zircon from ,ceylon that ,klaproth discovered the new earth1 ,zirconia1 in #aghi4ea ,in #agie he found the same earth in hyacinth1 and so showed the two to be identical4 #ea ,schriften der ,gesellschaft naturforschender ,freunde in ,berlin1 #aghi1 vol4 #i4 ,artificial crystals of zircon have been obtained by the action of silicon tetrachloride and silicon tetrafluoride on zirconia1 and by the action of zirconium tetrafluoride on silica at high temperatures4 ,zircon is one of the most widely distributed minerals known1 though usually it occurs in very small quantities4 ,good crystals have been found in ,new ,zealand1 in ,ceylon1 at ,miask in the ,urals1 and in ,north ,carolina4 ,this last deposit has been worked commercially for the extraction of zirconia for ,nernst lamps 7vide p4 #cbj74 ,it occurs in a decomposed felspar in a pegmatite dyke in the ,archan gneiss near ,zirconia1 ,henderson ,co41 and can be easily extracted by picking or washing1 after crushing if necessary4 ,should there ever be a considerable demand for zirconia1 it could doubtless be saved as a by-product in the extraction of thoria from monazite sands 7q4v471 zircon being very generally found in those sands 7see below74 ,zircon is common in crystalline rocks1 limestones1 schists1 syenites1 granites1 etc4 ,it is a constant accessory constituent in the acid igneous rocks1 especially in the more acid eruptive rocks4 ,it is readily detected under the microscope by the pleochroic haloes with which the tiny crystals are surrounded2 these have been shown by ,joly to be due to alteration of the surrounding rock by the radiations emitted by the radio-active constituents of the zircon4 ,it also occurs as a constituent of those sands which are formed by the erosion of the igneous rocks in which it is enclosed1 and hence it almost invariably accompanies monazite in the so-called monazite sands4 ,zircon is one of the least easily altered minerals2 by the prolonged action of chalybeate and other waters1 during many geological ages1 however1 it gradually changes1 losing silica and gaining lime1 oxides of iron1 and water4 ,some of these altered varieties have received special names1 as1 e4g4 ,auerbachite1 ,malacone1 ,cyrtolite1 and ,alvite2 but none of them is of special interest4 ,naegite4#eb--,this rare mineral is a silicate closely related to zircon1 but of rather more complex composition4 ,it may be represented as silicate of zirconium1 ,zr,si,o 7zirconia #eec1 silica #bjf per cent471 with rare earths 7chiefly yttria1 #ia per cent471 uranium 7,,uo #c per cent471 and thorium 7,th,o #ej per cent471 partly as silicates1 partly as columbates and tantalates 77,cb1,ta7,o #gg per cent474#ec #eb ,beitrge zur ,mineralogie von ,japan1 #aijf1 #b1 #bc4 #ec ,an earlier analysis 7,abstr4 ,chem4 ,soc4 #aije1 #hh1 ii41 #agg7 gave over #bj per cent4 of uranous oxide1 ,,uo2 the greater part of this appears to have been zirconia1 ,zi,o4 ,it is tetragonal1 usually occurring in globular aggregates of crystals4 ,the measurable angles are extremely close to those of zircon1 and it is probable that naegite is isomorphous with the series mentioned above under ,thorite4 ,the hardness is #g1 the sp4 gr4 #djia4 ,the colour is dark green or brown1 becoming dull by weathering4 ,the double refraction is extremely weak4 ,so far it has only been found in the #8placer' tin deposits or #8gravel tin' of ,japan4 99 99 99 99 99 ,the following minerals 7see list7 are also to be included in this sub-class3 ,alvite 7,anderbergite or ,cyrtolite71 ,auerbachite1 ,malacone1 ,oerstedite and ,tachyaphaltite1 altered varieties of zircon4 ,calciothorite1 ,eucrasite and ,freyalite1 altered varieties of ,thorite4 ,pilbarite1 ,thorogummite and ,yttrogummite1 hydrated silicates of thorium with uranium and other metals4 7c7 ,,complex ,,silicates ,eudialyte 7,eucolyte74--,this is a complex silicate of alkalies1 lime1 ferrous oxide1 rare earths1 etc41 containing chlorine and a high proportion 7up to #ag per cent47 of zirconia4 ,the empirical formula is given by ,dana as ,na7,ca1,fe7,cl7,si1,zr7,o4 ,brgger gives the simpler metasilicate formula ,r,r,zr7,si,o71 where ,r 7,na1,k1,h71 ,r 7,ca1,fe1,mn1,ce,o,h71 and ,zr7,o,cl7 may partly function as an acid in place of ,si,o4 ,the true formula1 however1 is quite uncertain1 as the zirconia may function either as an acidic or basic oxide4 ,the fact that a mineral of such exceedingly complex composition occurs in perfectly well-defined crystals indicates the intricate nature of the problems to be solved in mineral chemistry4 ,the crystals are rhombohedral1 a 3 c #a 3 #baaaf4 ,common forms are--the pinakoid c #aaa1 prisms a #aja1 and m #baa1 and pyramids r #ajj and e #aaj4 c r #ca #bb4 ,habit tabular parallel to c1 rhombohedral with e prominent1 or prismatic with a prominent4 ,cleavage c very good1 a difficult4 ,the colour is brown or red to brownish- or bluish-red4 ,brittle4 ,hardness #e to #e2 sp4 gr4 #bib for eudialyte1 #cj to #ca for eucolyte4 ,the double refraction is strong1 being positive for eudialyte1 negative for the ,norwegian variety1 eucolyte4 ,from careful microscopic examination1 ,ramsay has found that zones of positive and negative birefringence1 as well as isotropic 7singly-refracting7 zones can occur on the same crystal1 and he suggests that the mineral is really composed of two isomorphous compounds forming mixtures4 ,in view of the continuous variation of optical properties in an isomorphous series like the felspars1 such an explanation seems doubtful4 ,the optical behaviour of minerals is very often anomalous1 and the phenomena in this case are probably due to repeated twinning1 with some alteration in the double refraction1 or to the lamellar intergrowth of two varieties having slightly different optical properties4 ,on heating1 the mineral evolves moisture and readily fuses4 ,it is easily attacked even by dilute acids1 being named by ,strohmeyer 7#ahai7 on account of this property4 ,the dilute hydrochloric acid solution reddens turmeric paper--a test for the presence of zirconium4 ,it is found in ,greenland1 usually embedded in felspar1 in ,norway1 in ,lapland and in ,arkansas1 being generally associated with minerals rich in alkalies1 e4g4 girine1 lolite1 nepheline1 sodalite1 arfvedsonite1 etc4 ,beckelite4--,this is a mineral similar in composition to eudialyte1 though not so complex1 and of more recent discovery4#ed ,it is a silicate of ceria earths and lime1 in which zirconia replaces silica2 the oxygen ratio 7i4e4 ratio of oxygen in basic oxides to oxygen in acid oxides7 is #c 3 #a1 and the formula ,ca,r7,si1,zr7,o1 where ,r rare earth metals1 chiefly of the cerium group4 ,it is thus a salt of an acid ,h,si,o #c;,h,si,o #c7c;,h,o1,si,o7 with zirconium and silicon vicarious4 #ed ,abstr4 ,chem4 ,soc4 #aije1 #hh1 ii1 #agg4 ,the crystals appear to belong to the cubic system1 occurring in cuboid grains1 and in octahedra and dodecahedra4 ,it is brown1 and isotropic1 with cubic cleavage4 ,sp4 gr4 #dae4 ,it is soluble in hot hydrochloric acid1 even after ignition2 the solution gives the turmeric test for zirconium4 ,it was found in a dyke in an lolite syenite1 near the ,sea of ,azov4 99 99 99 99 99 ,the following minerals 7see list7 are also to be placed in the class of mixed silicates3 ,arfvedsonite and cataplejite1 complex zircono-silicates4 ,hiortdahlite 7,guarinite7 and ,lavenite1 zircono-silicates with fluorine4 ,caryocerite1 ,melanocerite and ,steenstrupine1 complex fluosilicates4 ,auerlite1 ,britholite1 ,erikite and ,florencite1 phospho-silicates4 ,cappelenite1 ,homilite and ,tritomite1 boro-silicates4 ,,chapter ,,iii ,,the ,,titano-,,silicates ,,and ,,titanates 7a7 ,,the ,,titano-,,silicates ,yttrotitanite or ,keilhauite4--,a titano-silicate of calcium1 aluminium1 iron and yttrium metals4 ,the mineral is isomorphous with titanite1 ,ca,o1,ti,o1,si,o 7q4v471 and is itself probably an isomorphous mixture of titanite with the silicate 7,y1,al1,fe7,si,o1 where ,y yttrium metals4 ,its composition will then be represented by the formula m 7,y1,al1,fe77,si,o7 n ,ca,ti7,si,o74 ,it is monoclinic1 with axial ratios and angles very close to those of titanite4 ,usual forms--pinakoids a #ajj and c #jja1 hemi-prism m #aaj1 hemi-pyramids n #aaa1 e #aaa and l #aab4 ,cleavage n distinct4 ,birefringence weak1 ve4 ,colour brown to brownish-black4 ,hardness #f2 sp4 gr4 #ceb to #cgg4 ,the mineral is fusible before the blowpipe1 and is decomposed by hydrochloric acid4 ,it was named by ,scheerer in #ahdd from its composition1 and by ,ekeberg in the same year in honour of the ,norwegian geologist ,keilhau4 ,titanite or ,sphene4--,this species1 important as an accessory mineral of many rocks1 is a titano-silicate of calcium1 generally containing small quantities of aluminium and iron4 ,the approximate formula usually given1 ,ca,ti,si,o1 is unsatisfactory2 some specimens contain as much as #g per cent4 of ferric oxide1 others up to #b per cent4 of manganese1 whilst the percentage of titanium oxide1 ,ti,o1 varies very considerably 7#cj to #de per cent474 ,zambonini and ,nickolan have independently analysed specimens for which no satisfactory formul could be deduced4 ,for specimens containing trivalent metals1 ,groth considers the mineral to be an isomorphous mixture of ,ca,ti,si,o and ,r,si,o 7see under ,yttrotitanite1 above72 ,blomstrand1 however1 advances the formula #b7,r,r,o1,ti,o7,o1,si,o1 where ,ti,o is basic1 and the trivalent metals occur in the divalent group ,r,o2 this formula is also supported by ,zambonini4 ,more recently the problem of the constitution has been attacked by ,bruckmoser1 using ,tschermak's method of determining the nature of the salts present in silicates4 ,in this method1 the mineral is digested with hydrochloric acid1 at a temperature not greater than #fj1 until decomposition is complete2 the silicic acid formed is washed by decantation1 and dried in air at a constant temperature2 it is weighed at regular intervals until the weight is constant4 ,it is stated that if a curve of times and weights be plotted1 a break is observed at the point where drying ceases 7for the acid is of course wet7 and decomposition begins2 the composition at this point1 which is taken as the composition of the acid required1 can be determined from the weight of the acid1 and the weight of anhydrous silica present1 which is determined by ignition after the weight has become constant4 ,employing this method in the case of titanite1 ,bruckmoser claims to have obtained the acids ,h,si,o and ,h,ti,o4 ,he therefore concludes that the constitution of the mineral is represented by the formula ,si,o1,ti,o,ca1 which presumably may be written ,ca7,ti1,si7,o4 ,crystal system--monoclinic2 a 3 b 3 c #jgedg 3 #a 3 #jhedc4 #fj #ag4 ,common forms 7,des ,cloizeaux's orientation7--the pinakoids a #ajj and c #jja1 with m #aaj1 s #jba1 x #ajb1 n #aaa1 and many others4 7#ajj7 7#aaj7 #ch #ad2 7#jja7 7#aja7 #fe #eg2 7#jja7 7#jaa7 #cf #cd4 ,the habit is very varied1 the commonest being the wedge form1 elongated c4 ,twinning is fairly common1 especially on the law--,twin plane a1 which gives both contact and interpenetrant twins4 ,cleavage m1 fairly distinct4 ,hardness #e to #e2 sp4 gr4 #cdj to #cef4 ,lustre adamantine to resinous4 ,the colour varies very much1 doubtless with the content of iron and manganese2 it is commonly yellow1 green1 or brown4 ,pleochroism is very distinct4 ,the refraction and dispersion are very high1 giving the facetted stone a #8fire' inferior only to that of diamond4 ,birefringence positive1 strong2 the axial angles vary very widely in different specimens4 ,it is fusible with difficulty before the blowpipe4 ,hot concentrated hydrochloric acid decomposes it partially1 with separation of silica2 boiling sulphuric acid1 or1 better1 fused potassium hydrogen sulphate1 decomposes it completely4 ,on account of the high dispersion and refractive index1 clear specimens of sphene make very beautiful gems1 but the stone is not sufficiently hard to stand much wear4 ,the mineral was discovered in ,chamouni by ,pictet in #aghg1 and was named ,pictite by ,delamtherie 7#agig74 ,in #agie ,klaproth analysed a specimen from ,passau1 and1 observing the presence of titanium 7which he had just discovered in rutile71 proposed the name ,titanite4 ,the mineral described by de ,saussure 7#agif7 as #8,schorl rayonnante1' and afterwards by ,hauy 7#ahja7 as ,sphene 7 a wedge71 was shown to be identical in composition with titanite by ,cordier1 and also by ,klaproth 7#ahaj72 the crystallographic identity was proved by ,g4 ,rose 7#ahbj74 ,on account of the difference in colour and composition1 a large number of varieties are distinguished4 ,the ordinary yellow and brown varieties are known indifferently as sphene or titanite4 ,ligurite has an apple-green colour2 ,semeline is a greenish form named from a fancied resemblance to flax seed4 ,lederite is a brown variety of tabular habit2 ,greenovite is rose-coloured1 and contains manganese4 ,alshedite and ,eucolite-,titanite are rich in the trivalent metals2 ,grothite is a brown variety containing a considerable percentage of ferric iron4 ,yttrotitanite1 which contains a high proportion of rare earths1 is usually treated as a separate species 7see above74 ,titanomorphite and ,leucoxene are white amorphous varieties chiefly produced by alteration of rutile and ilmenite4 ,titanite is a fairly widespread mineral2 as an accessory rock constituent it is common in the massive plutonic rocks in tiny crystals1 readily distinguished under the microscope by the high refraction and birefringence1 whilst in large embedded crystals it occurs in many granular limestones1 and in plutonic acid1 as well as in some metamorphic rocks4 ,in good crystals it is found in many parts of ,switzerland and the ,alps1 in ,dauphin1 the ,tyrol1 ,piedmont1 the ,urals1 ,south ,norway1 and other ,european localities2 it is also widely distributed in the ,united ,states and ,canada4 ,the mineral is important as a valuable source of titanium4 99 99 99 99 99 ,the class of ,titano-silicates is a very large one1 and might be extended almost at will by the inclusion of the numerous silicates which contain titanium4 ,owing to the frequency with which small quantities of silica are replaced by titanium dioxide1 almost all the commoner silicate minerals contain the latter oxide1 so that titanium is one of the most widely distributed of the elements4 ,relatively very few1 however1 of the titanium-bearing minerals contain the element in considerable quantities1 and only two or three have any importance as commercial sources of titanium compounds4 ,only those additional titano-silicates which contain titanium as an important constituent are mentioned below2 short accounts will be found in the alphabetical list4 ,johnstrupite1 ,mosandrite1 ,rinkite1 ,rosenbuschite and ,tscheffkinite are complex titano-silicates containing yttrium or cerium metals4 ,astrophyllite1 ,leucosphenite1 ,molengraafite1 ,neptunite and ,rhnite are complex titano-silicates free from rare earth elements4 ,benitoite is a simple titano-silicate of barium2 nigmatite and ,narsarsukite contain iron and sodium2 ,lorenzenite has sodium and zirconium4 ,schorlomite is a titaniferous garnet4 ,a variety of olivine rich in titanium 7,titanium ,olivine7 is also known4 7b7 ,,the ,,titanates ,yttrocrasite4#ee--,this is a complex titanate of rare earths 7chiefly yttria earths7 with lime1 thoria1 and oxides of lead1 iron1 uranium1 etc42 it has a considerable water content4 ,an approximate formula is ,r,o1,riv,o1#c,r,o1#af,ti,o1#f;,h,o1 where ,r 7,ca1,pb1,fe71 ,riv 7,th1,u71 and ,r,o rare earths4 ,no constitutional formula can be given2 it will be noticed that the amount of titanium dioxide is considerably more than is required to combine with the bases present 7cf4 also ,delorenzite below74 ,it is radioactive4 #ee ,hidden and ,warren1 ,amer4 ,j4 ,sci4 #aijf1 iv41 #bb1 #eae2 also ,zeitsch4 ,kryst4 ,min4 #aijg1 #dc1 #ah4 ,imperfect crystals only were found1 apparently belonging to the orthorhombic system4 ,no crystallographic data could be determined4 ,the mineral is black1 closely resembling polycrase and euxenite 7q4v47 in appearance4 ,hardness #e-f2 sp4 gr4 #dhj4 ,it is infusible1 and not easily soluble in acids4 ,hydrofluoric acid decomposes it1 and the powdered mineral is also slowly attacked by boiling concentrated sulphuric acid4 ,it was found in #aijd by ,barringer1 in ,burnet ,co41 ,texas4 ,delorenzite4#ef--;,a compound similar to the above1 but even richer in titanium dioxide1 which amounts to #ff per cent4 ,tin dioxide is also present1 with traces of columbic anhydride4 ,the bases are the yttria earths 7almost free from ceria earths71 uranium dioxide1 and some ferrous oxide1 the formula being #b;,fe,o1,,uo1#b,y,o1#bd,ti,o1 with a little ,sn,o replacing ,ti,o4 ,it is strongly radioactive4 ,its closest chemical neighbour is yttrocrasite1 but in appearance and angles it closely resembles polycrase 7q4v474 ,its discoverer1 ,zambonini1 therefore formulates it as a metatitanate with titanium acting also as a base--polycrase is a mixed metatitanate and metacolumbate--thus1 #b;,fe,ti,o ,u7,ti,o7 #b,y7,ti,o7 #g7,ti,o7,ti,o4 #ef ,zambonini1 ,zeitsch4 ,kryst4 ,min4 #aijh1 #de1 #gf4 ,the crystals occur in aggregates of numerous individuals in sub-parallel growth4 ,the system is orthorhombic2 a 3 b 3 c #jccge 3 #a 3 #jcdab4 ,usual forms--the pinakoids a #ajj and b #jaj with prism m #aaj1 dome d #bja1 etc4 ,habit prismatic1 elongated c axis4 ,hardness #e-f2 sp4 gr4 about #dg4 ,it was found with struvite in a pegmatite at ,craveggia1 ,piedmont1 ,italy4 ,ilmenite or ,menaccanite 7,specular ,iron ,ore1 ,titaniferous ,ironstone1 etc474--,this is a titanate of iron1 usually written ,fe,ti,o4 ,its constitution has given rise to very considerable discussion#eg2 not only do the relative proportions of iron and titanium vary greatly1 but the iron is undoubtedly present in both the ferrous and the ferric states1 and in the former state is partly replaced in some specimens by manganese and magnesium4 ,in #ahbi ,mosander put forward the view that the mineral consisted of ,fe,ti,o1 ferrous titanate1 with varying proportions of ferric oxide1 the forms and angles of ilmenite being very similar to those of hmatite1 ,fe,o4 ,this view was disputed by ,h4 ,rose1 who concluded that the mineral must have been originally an isomorphous mixture of ferric oxide1 ,fe,o1 and titanic oxide1 ,ti,o1 which on exposure to high temperature in the earth's crust would change according to the equation ,fe,o ,ti,o #b,ti,o #b;,fe,o so that the proportion of ferrous iron increases with the proportion of titanium dioxide1 as is actually found to be the case4 ,this condition1 however1 is also satisfied by ,mosander's view4 ,the latter view was also supported by ,rammelsberg1 who pointed out that the presence of magnesium indicated the existence of ferrous iron as a primary constituent4 ,additional support is lent to this view by the discovery of ,pyrophanite1 ,mn,ti,o 7see list71 which is found to be isomorphous with ilmenite1 so that there can be little doubt that ,mg,ti,o1 which can be only a titanate1 would1 if it existed in the crystalline form 7see ,geikielite in list71 also be isomorphous with ilmenite4 ,friedel and ,gurin 7#ahgf7 prepared artificial titanium sesquioxide1 ,ti,o1 and found it to be isomorphous with hmatite1 ,fe,o2 they concluded that ,fe,fe,o1 ,fe,ti,o and ,ti,ti,o formed an isomorphous series1 and that ilmenite was a mixture of the second with the other two4 ,in #ahij ,hamberg pointed out that there was no reason to suppose that hmatite1 ,fe,o1 contains ferrous iron1 i4e4 has the constitution ,fe,feiv,o1 analogous to ,fe,tiiv,o1 since in corundum1 the analogous compound of aluminium1 ,al,o1 divalent aluminium can hardly exist2 nevertheless1 strict analogy of constitution is not necessary for isomorphism1 as shown by the case of potassium nitrate1 ,,kno1 and aragonite1 ,ca,c,o1 so that hmatite1 ,fe,o1 and ferrous titanate1 ,fe,ti,o1 might form solid solutions in varying proportions without the strictly analogous formula ,fe,fe,o being true for the former4 ,the balance of opinion inclines to the constitution 7m,fe,ti,o n,fe,o in isomorphous mixture7 originally proposed by ,mosander4 ,the evidence in support of this view has been greatly strengthened by the recent work of ,manchot1#eh which has proved the absence of titanium sesquioxide1 ,ti,o2 the mineral is therefore to be regarded as a titanate4 #eg ,for a full account of the earlier work on the constitution of ilmenite vide ,hintze1 i4 #aheh et seq4 #eh ,zeitsch4 anorg4 ,chem4 #aiab1 #gd1 #gi4 ,crystal system--rhombohedral2 in forms and angles very close to hmatite1 but the two differ in symmetry 7hmatite has t1 #c1 c1 #c2 ilmenite has only t1 c74 c #achdeh2 7#aaa7 7#ajj7 #eg #eh2 habit1 tabular1 thick2 or in thin lamin4 ,usually in embedded grains or rolled crystals in sand4 ,hardness #e to #f2 sp4 gr4 #de to #ej1 increasing with percentage of ferric oxide4 ,iron black1 opaque2 streak black to brownish-red4 ,lustre sub-metallic4 ,slightly magnetic4 ,the mineral is infusible2 when powdered1 it dissolves slowly in boiling hydrochloric acid1 the filtered yellow solution giving the characteristic blue colouration of titanium salts on addition of tinfoil4 ,in fused potassium hydrogen sulphate it dissolves readily4 ,the variation in composition can be judged from the following limits3 ,ti,o ,fe,o ,fe,o #ce #icf #cc per cent4 #ebh #ab #dfe ,ilmenite is a widely distributed mineral4 ,in crystals it occurs chiefly at ,krager and ,arendal in ,norway1 at ,miask in the ,ilmen mountains1 in ,dauphin1 the ,st4 ,gothard1 etc42 in the massive form at ,bay ,st4 ,paul1 ,quebec1 and other localities in ,america2 and in sands at ,menaccan in ,cornwall1 ,iserwiese in ,bohemia1 ,puy de ,dme1 dp4 ,haute ,loire1 ,france1 and in ,brazil1 ,australia1 and ,new ,zealand4 ,the mineral was discovered at ,menaccan in ,cornwall by ,mc,gregor1 about #agij4 ,he described it as containing iron and a new oxide2 the unknown oxide was obtained in #agie from rutile by ,klaproth1 who gave the name ,titanium to the new metal it contained4 99 99 99 99 99 ,short descriptions of the following titanates are also given 7see list73 ,davidite and ,knopite2 these are complex titanates containing elements of the cerium and yttrium groups4 ,arizonite and ,pseudobrookite--ferric titanates4 ,perovskite1 calcium titanate1 and its variety ,hydrotitanite4 ,pyrophanite1 a manganese titanate isomorphous with ilmenite1 and ,senaite1 a species intermediate in composition between these two4 ,geikielite1 the magnesium analogue of ilmenite1 with the variety ,picroilmenite1 which is rich in iron4 ,uhligite1 a titanate of zirconium1 calcium and aluminium4 ,derbylite1 ,lewisite and ,mauzeliite1 an interesting series of titano-antimonates4 ,warwickite1 a boro-titanate4 ,,chapter ,,iv ,,the ,,tantalo-,,columbates 7a7 ,,tantalo-,,columbates ,,containing ,,no ,,titanium ,,dioxide ,samarskite1 ,yttro-ilmenite or ,eytlandite 7,urano-tantalite74--,samarskite is a tantalo-columbate#ei of the rare earth metals1 with iron1 calcium1 and uranium4 #ei ,in this and all similar minerals1 columbium 7niobium7 and tantalum are to be regarded as vicarious2 they replace each other in all proportions4 ,it seldom happens that a pure columbate is found free from tantalum1 or vice versa2 one or other may predominate1 but the two are almost always found together4 ,rammelsberg gives the formula ,r,r7,cb1,ta7,o1 where ,r 7,fe1,ca1,,uo71 and ,r rare earth metals4 ,groth regards it as essentially a pyrocolumbate 7tantalate7 of rare earth metals ,r7,cb1,ta7,o the iron1 calcium and uranium being more or less accessory constituents4 ,des ,cloizeaux considers the formula indefinite4 ,the mineral has also been found to contain tin1 thorium1 germanium1 and helium4 ,the yttria earths usually predominate 7#aai to #ahi per cent471 the percentage of ceria earths being low 7#bd to #eb per cent474 ,the yttria earths contain the very rare oxide samaria4 ,the mineral is radio-active4 ,crystal system--orthorhombic2 a 3 b 3 c #jedef 3 #a 3 #jeagh4 ,forms--macro- and brachy-pinakoids a #ajj and b #jaj2 prisms m #aaj and h #abj1 the macrodome e #aja1 and pyramids p #aaa and v #bca4 ,angles--7#ajj7 7#aaj7 #bh #cg2 7#jja7 7#aja7 #dc #cj2 7#jja7 7#jaa7 #bg #bb4 ,habit usually prismatic1 with e prominent2 sometimes tabular parallel to a or b4 ,cleavage b1 imperfect4 ,the faces are usually rough4 ,the mineral commonly occurs massive1 and in flattened grains embedded in granite4 ,conchoidal fracture4 ,brittle4 ,hardness #e to #f2 sp4 gr4 #ef to #eh4 ,colour velvet-black1 streak reddish-brown4 ,opaque even in thin films4 ,before the blowpipe it fuses at the edges2 with borax it gives an iron bead4 ,it is decomposed by boiling concentrated sulphuric acid1 better by fusion with potassium hydrogen sulphate1 and leaching the residue with dilute hydrochloric acid--this leaves the insoluble oxides ,cb,o and ,ta,o4 ,on heating it glows1 with decrease in specific gravity 7cf4 p4 #ch74 ,samarskite occurs with other columbo-tantalates in felspar1 or in veins in granite1 near ,miask in the ,urals1 near ,quebec in ,canada1 and in ,mitchell ,county1 ,north ,carolina4 ,from the last-named locality1 masses up to twenty pounds in weight have been obtained4 ,the mineral was first discovered in the ,urals by ,ewreinoff1 captain of a corps of ,russian mountain engineers4 ,he sent a specimen for identification to the mineralogist ,gustave ,rose1 who pronounced it to be a tantalate of uranium containing manganese1 and called it ,urano-tantalite4#fj ,in #ahdg the chemist ,heinrich ,rose1 brother of ,gustave1 in the course of his researches on tantalic #8acid' 7oxide71 analysed a specimen4 ,he found the composition given above1 and renamed it ,samarskite1#fa in honour of the ,russian engineer who furnished him with the specimen for analysis4 #fj ,pogg4 ,ann4 #ahci1 #dh1 #eee4 #fa ,ibid41 #ahdg1 #ga1 #aeg4 ,in #aijg1 ,brgger#fb announced that ,annerdite1 of which he had published an account as a new species in #ahha1 was a parallel growth of the mineral columbite1 7,fe1,mn7,cb,o1 on samarskite4 #fb ,abstr4 ,chem4 ,soc41 #aijg1 #ib1 ii4 #hhe4 ,both minerals are orthorhombic1 but they are not isomorphous4 ,the mistake was due to the fact that whilst the crystallographic data were determined from the upper crystals of columbite1 the crystals of samarskite were used for analysis4 ,plumboniobite4#fc--,this is a recently discovered mineral closely related to samarskite and yttrotantalite 7q4v474 ,it is essentially a columbate#fd of yttrium metals1 lead and uranium1 with water1 ferrous oxide1 titanium dioxide1 stannic oxide1 alumina1 lime1 and cuprous oxide4 ,the formula given is ,r,cb,o1,r7,cb,o71 where ,r 7,fe1,pb1,ca1,,uo71 and ,r ,al and yttria metals1 with isomorphous 787 metatitanate4 ,the mineral is radio-active1 and gives considerable quantities of gas on being heated with sulphuric acid 7carbon dioxide #jai1 helium and nitrogen #jbb per cent474 ,the yttria earths are rich in the oxides of gadolinium and samarium1 and the mineral should prove a valuable source of these elements4 ,it is remarkable that the ceria earths are almost entirely absent4 #fc ,hauser u4 ,finch1 ,ber4 #aiji1 #db1 #bbgj2 ,hauser1 ibid41 #aiaj1 #dc1 #dag4 #fd ,it is to be understood that small quantities of columbium are replaced by tantalum4 ,the mineral is massive1 with some indication of crystalline structure4 ,it is dark brown to black1 transparent in flakes1 and under the microscope is seen to be isotropic1 with doubly-refracting inclusions1 undoubtedly of a secondary nature4 ,hardness #e to #e2 sp4 gr4 #dhj to #dha4 ,unlike samarskite1 it does not glow on ignition4 ,it occurs with mica and pitchblende in pegmatite veins in granite1 at ,morogoro1 in the ,uluguru ,mountains1 ,german ,east ,africa4 ,yttrotantalite4--,this is a tantalo-columbate similar in composition to ,samarskite1 and isomorphous with it2 though1 as the name implies1 the acidic oxide is chiefly tantalum pentoxide1 the percentage of columbic anhydride being much lower than in the latter mineral4 ,it is a pyro-salt of the formula ,r,r7,cb1,ta7,o #d;,h,o1#fe where ,r 7,fe1,ca7 and ,r rare earth 7chiefly yttrium7 metals 7,rammelsberg74 ,strutt found thorium and radium in it4 ,the manner in which the water is combined in this1 as in many other minerals1 is at present undetermined4 #fe ,dana gives ,r,r7,cb1,ta7,o #d;,h,o2 this appears to be an error4 ,crystal system--orthorhombic2 a 3 b 3 c #jedaa 3 #a 3 #aaccj4 ,common forms--pinakoids b #jaj and c #jja1 prisms m #aaj1 o #baj1 p #abj1 domes s #bja and #jaa4 ,habit1 prismatic with m and b prominent1 or tabular parallel to b4 ,colour yellow to black1 white after strong ignition4 ,it is found at ,ytterby in ,sweden1 and in ,south ,norway4 ,fergusonite1 ,tyrite1 or ,bragite4--,a columbate and tantalate of the rare earth metals1 with uranium1 iron1 calcium1 etc4 ,the general formula is that of an ortho-compound1 ,r,o17,cb1,ta7,o or ,r7,cb1,ta7,o1 where ,r metals of the rare earths1 chiefly of the yttrium group4 ,brgger includes the other constituents in the more complex formula 7,th1,u77,si1,sn7,o #ab,r7,cb1,ta7,o2 but the simpler formula agrees quite well with specimens from the most widely separated localities1 and is usually adopted4 ,the mineral is radio-active and contains helium4 ,tetragonal1 polar 7with tetrad axis of symmetry only7 c #adfdc4 7#jja7 7#aja7 #ee #dj4 ,common forms--,basal pinakoid c #jja1 tetragonal prism g #cbj1 pyramids s #aaa1 z #cba4 ,brittle4 ,hardness #e to #f2 sp4 gr4 #ehd1 decreasing on hydration4 ,lustre dull1 brilliantly vitreous on broken surfaces4 ,colour brownish-black4 ,translucent to opaque4 ,fergusonite was discovered by ,hartwell4 ,it occurs with samarskite1 and often with gadolinite and allanite1 in ,norway and ,sweden1 the ,carolinas1 ,texas1 the ,urals1 ,w4 ,australia1 etc4 ,on heating it glows suddenly between #ejj and #fjj;,c41#ff losing all its helium1 and with decrease in density 7#efai to #ecge74 ,at the same time it gives out a considerable amount of heat--#hji ,c4#fg for #a gm4 7see p4 #ch74 #ff ,ramsay and ,travers1 ,zeitsch4 physikal4 ,chem4 #ahih1 #be1 #efh4 #fg ,the heat of combustion of a gram of hydrogen is #cdb ,k4 ,sipylite4--,essentially a columbate of rare earth metals1 with oxides of tantalum1 tungsten1 zirconium1 uranium1 iron and calcium1 and some water4 ,mallet1 the discoverer1 gives the formula as ,r,o1,cb,o1 the basic oxides including1 besides the rare earths1 ,cb,o with ,ta,o and ,,wo1 and some water4 ,an alternative formula1 making it a complex pyro-salt1 is also given1 but from its great similarity in form and angles to fergusonite1 the first formula is preferred4 ,strutt finds that it contains not only uranium1 radium and helium1 but also thorium in considerable quantity 7,th,o #di per cent471 a fact which had been overlooked by ,mallet4 ,the rare earths contain a high proportion of erbia4 ,it is tetragonal1 c #adgfg1 7#jja7 7#aja7 #ee #ed4 ,the crystals are octahedral1 with the form p #aaa2 p p #gi #ae1 p p #abh #ej4 ,cleavage distinct p4 ,it is usually granular and amorphous4 ,colour brownish-black to brownish-red1 lustre resinous4 ,brittle4 ,hardness #f2 sp4 gr4 #dhi4 ,translucent4 ,its behaviour on heating has been already mentioned 7see p4 #ci72 it is infusible4 ,boiling hydrochloric acid partially dissolves it2 the solution gives the turmeric test for zirconium1 and on diluting and adding metallic tin a sapphire-blue colour is developed1 due to the columbium present4 ,boiling concentrated sulphuric acid decomposes it slowly4 ,it is found in ,amhurst ,co41 ,virginia1 adherent to the allanite which occurs there in large quantities4 ,it was discovered there by ,mallet in #ahgg1 who named it1 on account of the columbium 7niobium7 present1 from ,sipylus1 one of the sons of ,niobe4#fh #fh ,see ,mallet1 ,amer4 ,j4 ,sci4 #ahgg1 iii41 #ad1 #cig4 99 99 99 99 99 ,in this class1 also1 are to be included the following minerals 7see list73 ,nohlite and ,vietinghofite1 varieties of ,samarskite4 ,hjelmite and ,kochelite1 minerals closely related to ,yttrotantalite and ,fergusonite respectively4 ,koppite1 ,loranskite1 ,microlite and ,rogersite1 complex tantalo-columbates containing elements of the cerium or yttrium groups4 7b7 ,,tantalo-,,columbates ,,containing ,,titanium ,,dioxide schynite4--,a columbate and titanate of the cerium metals1 with thorium1 calcium1 iron1 etc4 ,from the results of an analysis on a specimen from ,hitter1 ,norway1 ,tschernik proposed the rather formidable formula #b7b;,ce,o1#c,ti,o71#d7,th,o1,ti,o71,y7, cb,o71#c7;,ca,o1,ti,o71#c;,fe7,cb,o71 ,fe7,ta,o71#f,ti,o4 ,this can be simplified to ,y7,cb,o7 ,th,ti,o ,ti,o1 in which ,y represents rare earth metals partially replaced 7#b atoms7 by ferrous iron 7#c atoms71 whilst thorium can be partially replaced by 7#b atoms of7 ferrous iron or calcium4 ,strutt found it to contain the uranium-radium combination and helium4 ,the crystals are orthorhombic1 holosymmetric2 a 3 b 3 c #jdhff 3 #a 3 #jfgcg4 ,common forms--brachy- and basal pinakoids b #jaj and c #jja1 prisms m #aaj and r #abj1 domes d #aja and v #jba1 with pyramid o #aaa4 7#ajj7 7#aaj7 #be #eg2 7#jja7 7#aja7 #ed #i2 7#jja7 7#jaa7 #cc #eh4 ,habit prismatic1 vertically striated1 or tabular parallel to b with horizontal striations4 ,brittle4 ,hardness #e to #f2 sp4 gr4 #di to #eg4 ,colour nearly black4 ,nearly opaque4 ,it occurs at ,miask1 in the ,urals1 at ,hitter in ,norway1 and at ,fredriksvarn4 ,the variety from the last locality is called ,polymignite2 it was shown by ,rose to be probably identical with schynite4 schynite was discovered by ,berzelius at ,miask and named by him from the ,greek 1 shame1 from the fact that its composition could not at that time be determined4 ,if the ceria earths be largely replaced by yttria earths1 a variety very similar in appearance and angles1 but approximating to polycrase 7q4v47 in composition1 is obtained4 ,this mineral was found in #ahgi1 and referred to schynite2 analysis subsequently showed its true composition1 and it was named ,blomstrandine 7q4v47 by ,brgger in #aijg4 ,the ,isodimorphous ,series ,euxenite1 ,polycrase1 ,blomstrandine1 and ,priorite4 ,euxenite and ,polycrase are members of an isomorphous series and vary considerably in composition4 ,the composition of the series is that of mixed columbates and titanates of yttria earths 7with1 as usual1 some ceria earths71 with uranium and zirconium1 and water4 ,before the isomorphous relation was recognised1 ,rammelsberg gave for ,euxenite the formula ,r7,cb,o71,r7,ti,o71#a;,h,o4 ,the ratio of the acidic oxides1 ,cb,o 3 ,ti,o1 is here #a 3 #b4 ,this is the greatest value of the ratio1 which varies for the series between #a 3 #b and #a 3 #e4fi ,the end members1 the pure metacolumbate and pure metatitanate respectively1 are unknown2 all the members occurring in nature are to be regarded as mixtures of these within the limits set by the ratios and 4 ,brgger#gj suggests that the name ,euxenite be retained for all members for which the ratio is between and 1 whilst for those minerals in which it is less than the name ,polycrase be kept2 these views have been supported by ,lange1 who has analysed members of the series4 #fi ,lange 7,abstr4 ,chem4 ,soc4 #aiaa1 #ajj1 ii4 #dii7 gives the limits and 4 #gj ,abstr4 ,chem4 ,soc4 #aijg1 #ib1 ii4 #hhe4 ,the members of this isomorphous series1 however1 are themselves dimorphous1 that is1 can each crystallise in two different ways4 ,the second form corresponding to the ,euxenites is known as ,priorite1 whilst that corresponding to ,polycrase is known as ,blomstrandine2 and these second forms are themselves members of a parallel isomorphous series of the same chemical composition1 of course1 as the first series4 ,it is1 perhaps1 undesirable to cite this as a typical example of an isodimorphous series1 since no end members of unmixed composition are known4 ,a perfect example of such a series is furnished by the oxides of antimony and arsenic4 ,each of these compounds exists in two distinct crystalline varieties1 antimony trioxide1 ,sb,o1 as ,valentinite 7orthorhombic7 and ,senarmontite 7cubic71 arsenic trioxide1 ,as,o1 as ,claudetite 7orthorhombic7 and ,arsenolite 7cubic72 and these two modifications are isomorphous with one another1 senarmontite with arsenolite1 and valentinite with claudetite4 ,in the case we are considering1 the name ,euxenite is applied to one crystalline modification 7,a7 of a number of isomorphous compounds within certain limits of composition1 the name ,priorite to the second crystalline modification 7,b7 of the same compounds2 the name ,polycrase is applied to compounds having the crystal form ,a1 and a composition varying within a second set of limits in the same chemical series1 whilst this second set of compounds in the crystalline form ,b is known as ,blomstrandine4 ,stated as concisely as possible1 the relationship is as follows3 ,each member of this chemical series of continuously varying composition can crystallise in two forms1 which are the same for every member4 ,the two varieties at one end of the series are called euxenite and priorite1 at the other end polycrase and blomstrandine4 ,thus1 whilst euxenite and priorite1 at the one end1 and polycrase and blomstrandine at the other1 have the same compositions1 euxenite and polycrase have the same crystalline form1 whilst priorite and blomstrandine have the same second crystalline form4 ,all four minerals have the same bright black appearance1 and bright conchoidal fracture2 they are all four isotropic1 probably as a result of hydration4 ,all are orthorhombic1 but the measurements for euxenite and polycrase are different from those for blomstrandine and priorite4 ,the two latter are not so widely distributed as the two former4 ,blomstrandine occurs at ,hitter1 ,arendal1 and other localities in ,norway2 priorite is found in ,swaziland1 ,south ,africa4 ,the crystal system of the ,polycrase-,euxenite series is orthorhombic1 but ,dana gives slightly different axial ratios for the two minerals4 ,this1 though ,brgger gives the same values for both1 is by no means incompatible with isomorphism1 as a glance at the axial ratios for the minerals aragonite1 strontianite1 witherite1 etc41 of the series of the orthorhombic carbonates1 will show4 ,brgger's ratios for the two are a 3 b 3 c #jcghi 3 #a 3 #jcebg2 ,dana gives for polycrase #jcdfb 3 #a 3 #jcabd1 for euxenite #jcfd 3 #a 3 #jcjc4 ,euxenite4 ,this species occurs usually in the massive form as a bright brownish-black mineral1 of hardness #f1 and sp4 gr4 #df to #ej4 ,the crystals are prismatic in habit2 the common forms are the pinakoids a #ajj and b #jaj1 the prism m #aaj1 the unit pyramid p #aaa1 and the dome #bja4 ,ramsay1 ,collie and ,travers found no helium in it2 ,boltwood found uranium1 radium and helium1 and ,strutt found in addition to these thorium4 ,as early as #ahgi1 ,blomstrand had observed zirconium in euxenite4 ,the mineral is infusible and with difficulty soluble in acids4 ,it occurs in many localities in ,scandinavia 7,hitter1 ,arendal1 ,brevig1 etc471 in ,north ,carolina1 ,south ,australia1 etc4 ,it was discovered by ,scheerer at ,jlster1 in ,norway1 in #ahci4 ,the ,euxenite-,polycrase series was studied by ,hauser and ,wirth in #aiji1ga in an endeavour to establish their theory that the proportions in which the various earths and acids occur in this group of minerals is subject to definite laws beyond the ordinary laws of combination4 ,thus of the erbia earths they state that the proportion of holmia and dysprosia increases relatively to erbia as titanium dioxide increases1 i4e4 as we pass from the euxenites to the polycrases2 at the same time scandia and yttria increase relatively to the other yttria earths 7the terbia group71 whilst in the ceria group samaria and praseodymia decrease relatively to the others4 ,thus samaria is found in appreciable quantities only when the titanium content is low4 ,the original paper must be consulted for full details4 #ga ,ber4 #aiji1 #db1 #dddc4 ,it was stated above that zirconium was found in euxenite in #ahgi4 ,in #aija ,hofmann and ,prandtl#gb declared that zirconia was an unfailing constituent of the mineral1 and that it was always accompanied by a new oxide1 which they named ,euxenia 7#8,euxenerde'74 ,this was characterised by the solubility of its oxalate in acid solutions1 the insolubility of the precipitated hydroxide in excess of alkali1 and the gradual precipitation by hydrogen peroxide from a slightly acid solution of its salts4 ,in their paper quoted above1 ,hauser and ,wirth state that zirconia is never present in typical euxenites4 ,in a second paper#gc they state that after exhaustive treatment of every known zirconia mineral1 they can find no trace whatever of the #8new earth1' and conclude that ,hofmann and ,prandtl must have made some experimental error4 ,during this examination1 they observed radioactivity in some minerals which contained no traces of uranium or thorium4 #gb ,ibid4 #aija1 #cd1 #ajfd4 #gc ,ber4 #aiaj1 #dc1 #ahjg4 ,risrite4#gd--;,a columbate of yttria earths1 with titanium2 ferric oxide1 alumina1 lime and lead monoxide are present in small quantities4 ,it resembles fergusonite in composition1 but differs in the almost complete absence of uranium1 the high loss on ignition1 and the amount of titanium present1 which is here considerable 7,ti,o #fe per cent474 ,hauser regards it as an orthocolumbate1 ,r7,cb1,ta7,o1 with an isomorphous admixture of metatitanate1 ,r7,ti,o74 #gd ,hauser1 ,ber4 #aijg1 #dj1 #caah2 ,zeitsch4 anorg4 ,chem4 #aijh1 #fj1 #bcj4 ,the rare earths are chiefly yttria1 with some erbia earths and a little terbia2 ceria1 lanthana and didymia are also present4 ,the mineral contains a considerable amount of helium1 which is remarkable in view of the very small content of uranium and thorium 7cf4 ,thalenite74 ,it is radioactive1 the active constituent being precipitated with the lead 7and to a very small extent with the rare earths74 ,it is infusible1 but at a red heat it loses much water1 and becomes very brittle1 with increase of specific gravity2 no glowing is observed4 ,it is attacked by boiling concentrated sulphuric acid1 and by fused potassium bisulphate2 also by hydrofluoric acid 7#dj per cent471 with separation of the insoluble rare earth fluorides4 ,no good crystals have been found1 and no crystallographic data are known2 examined by polarised light it appears isotropic1 but this may be due to alteration4 ,colour1 yellowish- to greenish-brown4 ,streak1 yellowish-white4 ,hardness #e2 sp4 gr4 #dagi1 increasing to #dfgh after ignition 7cf4 p4 #ch74 ,the mineral was found in a granite-pegmatite at ,risr1 ,south ,norway4 ,wiikite4#ge--;,a mineral of very complex composition1 for which no definite formula can be assigned4 ,its chemical nature may be understood from the following analytical data3 ,columbic and tantalic anhydrides #afj2 ,dioxides of titanium and zirconium #bcd2 ,silica #agj2 ,ceria #be2 ,yttria #gf2 ,scandia #ab2 ,thoria #ee2 ,ferrous oxide #aee2 ,uranic oxide #cf2 water 7and gas7 #eh per cent4 #ge ,crookes1 ,phil4 ,trans4 #aijh1 ,a1 #bji1 #ae4 ,traces of lime1 magnesia1 stannic oxide and sulphur are also present4 ,the mineral is infusible2 on heating1 helium1 sulphuretted hydrogen and water vapour are given off1 and a white sublimate is formed4 ,the evolution of gas is almost explosive1 the mineral breaking with a curious fracture4 ,it is black and perfectly amorphous1 showing no trace of crystalline structure or action on polarised light4 ,hardness1 #f2 sp4 gr4 #dhe4 ,wiikite is partially attacked by acids1 readily by fused potassium bisulphate4 ,it is radioactive4 ,the mineral was found with monazite in a felspar quarry at ,impilaks1 ,lake ,ladoga1 ,finland4 ,it is important as the source of scandium used by ,sir ,william ,crookes in his investigations of that element2 some specimens of the mineral contain over #a per cent4 of the oxide 7see p4 #dd74 99 99 99 99 99 ,the following related minerals1 of which descriptions are given in the alphabetical list1 are to be included here3 ,arrhenite1 ,chalcolamprite1 ,endeiolite and ,whlerite1 are complex tantalo-columbates containing silica4 ,hainite contains both silicon and titanium4 ,dysanalyte is a titano-columbate believed by ,hauser#gf to be merely an impure form of perovskite 7see p4 #ad74 #gf ,vide ,zeitsch4 anorg4 ,chem4 #aijh1 #fj1 #bcg4 ,ilmenorutile and ,strverite are closely allied minerals believed by ,prior#gg and ,schaller#gh to be isomorphous mixtures of rutile with ,tapiolite or ,mossite 7ferrous tantalo-columbates74 #gg ,min4 ,mag4 #aijh1 #ae1 #gh4 #gh ,abstr4 ,chem4 ,soc4 #aiab1 #ajb1 ii4 #ggc4 ,pyrochlore is a complex titano-columbate containing elements of the cerium or yttrium groups4 ,blomstrandite is an hydrated titano-columbate of rare earth elements1 with calcium and uranium2 it must not be confused with blomstrandine4 ,,chapter ,v ,,the ,,oxides ,,and ,,carbonates 7a7 ,,the ,,oxides ,uraninite or ,pitchblende4--,uraninite consists essentially of oxides of uranium 7,,uo ,,uo #ge to #he per cent471 associated with thoria1 zirconia1 rare earths1 beryllia1 and oxides of lead4 ,traces of lime1 iron oxides1 silica1 bismuth1 and arsenic are also sometimes present1 with water in widely varying quantities4 ,nitrogen and helium are always found in it1 and1 of course1 radium4 ,groth regards pitchblende as uranous uranate ,uiv7,uvi,o71 the uranium in the acidic radicle being hexavalent and in the basic radicle tetravalent1 and in the latter condition partially replaced by lead1 thorium1 and rare earths4 ,szilard#gi regards it rather as a loose compound or even a solid solution of oxides of thorium and uranium1#hj with small quantities of other oxides1 he having obtained apparently homogeneous 7though non-crystalline7 bodies by dissolving thorium hydroxide in solutions of uranium salts and evaporating to dryness4 #gi ,compt4 rend4 #aijg1 #ade1 #dfc4 #hj ,see under ,thorianite1 infra4 ,the cubic form of the crystalline varieties has been taken as indicating that the mineral is really a spinel1#ha but it is difficult to see how the general formula of that group can be considered comparable to the uranyl uranate formula1 ,,uo1,,uo1 for pitchblende4 #ha ,the ,spinels are an isomorphous family of cubic minerals of the general formula ,r,o1,r,o1 where ,r ,be1 ,fe1 ,mg1 ,ca1 etc41 and ,r ,fe1 ,al1 ,cr1 etc4 ,crystals are rare1 and belong to the cubic system1 the common forms being the octahedron o #aaa and the dodecahedron d #aaj2 the cube a #ajj is sometimes present4 ,the mineral is massive1 usually botryoidal4 ,the crystalline or primary form is black1 with hardness #e1 sp4 gr4 #ij to #ig2 the altered varieties are grey to greenish- and brownish-black1 sp4 gr4 #ej to #fd4 ,it is infusible before the blowpipe1 but readily soluble in nitric acid4 ,the mineral occurs both as a primary and secondary constituent of rocks2 as a primary mineral it is found in ,norway1 ,north ,carolina1 etc42 as a secondary species it occurs in the massive and hydrated form1 with ores of lead1 silver1 tin1 etc41 in ,saxony and ,cornwall1 and at the celebrated mine of ,joachimsthal1 in ,bohemia4 ,the latter deposits1 consisting of the massive and altered varieties1 for which the name ,pitchblende is generally reserved1 have been much used as a source of radium1 especially those at ,joachimsthal1 and the ,cornwall ore4 ,several varieties of uraninite have been distinguished by special names4 ,crystalline varieties from ,annerd and ,arendal in ,norway are known as ,brggerite and ,cleveite respectively2 ,nivenite is a third form4 ,in these varieties uranium oxides have been replaced to a considerable extent by the rare earths and thoria4 ,an amorphous variety of doubtful composition1 produced by alteration1 is known as ,gummite2 ,uranosphrite is a similar altered form4 ,thorianite4#hb--,this interesting mineral consists chiefly of thoria1 ,th,o 7#ee-gi per cent471 with oxides of uranium 7#aa-cb per cent471 and ceria oxides 7#a-h per cent472 oxides of lead and iron are also present in small quantities1 and zirconia with silica1 probably due to associated zircon4 #hb ,dunstan and ,blake1 ,proc4 ,roy4 ,soc4 #aije1 ,a1 #gf1 #bec2 ,dunstan and ,jones1 ibid41 #aijf1 ,a1 #gg1 #edf4 ,helium is present1 and the mineral is strongly radioactive4 ,a careful analysis by ,hahn#hc shows traces of many metals2 the same chemist has also separated an extremely active component1 #bej1jjj times as active as thorium nitrate1 which he calls ,radiothorium4 #hc ,hahn1 ibid41 #aijg1 ,a1 #gh1 #che4 ,the composition has been accounted for 7,dunstan and ,jones1 loc4 cit47 on the hypothesis that thoria 7,th,o7 and uranous oxide 7,,uo7 are isomorphous1 the mineral being really a solid solution4 ,whilst1 however1 the crystal system of the natural body is really rhombohedral 7vide infra7 the two pure oxides appear to be cubic4 ,thus ,troost and ,ouvrard#hd obtained artificial thoria in minute octahedra2 and1 similarly1 ,hillebrand#he obtained uranous oxide in octahedra by reduction of uranyl chloride1 ,,uo,cl1 though his work seems to be open to objection4 ,on the other hand1 the same author#hf found that uranous oxide and thoria1 fused together in almost any proportions1 gave a homogeneous body crystallising in octahedra 7cf4 ,szilard1 ,compt4 rend4 #aijg1 #ade1 #dfc1 quoted under ,uraninite74 ,the probability of the isomorphism of the oxides is strengthened by the observation of isomorphism in the sulphates4 ,as early as #ahhf1 ,rammelsberg showed that uranous sulphate1 ,u7,,so71 crystallises with nine molecules of water and is isomorphous with the corresponding thorium sulphate1 ,th7,,so71#i;,h,o2 and six years later1 ,hillebrand and ,melville#hg obtained mixed crystals of the two sulphates which were exceedingly close in forms and angles to those of pure uranous sulphate4 ,it is then at least probable that the two oxides are isomorphous1 though the point cannot be regarded as satisfactorily proved1 by reason of the anomalous crystal forms of the naturally occurring mixtures1 thorianite and uraninite4 ,the recent results of ,kobayashi#hh point to the conclusion that different varieties of thorianite may exist1 in each of which the oxides of thorium and uranium bear definite simple ratios to one another4 #hd ,compt4 rend4 #ahhb1 #ajb1 #adbb4 #he ,zeitsch4 anorg4 ,chem4 #ahic1 #c1 #bdc4 #hf ,bull4 ,u4,s4 ,geol4 ,surv4 ,no4 #aac1 #ahic4 #hg ,ibid4 ,no4 #ij1 #ahib1 p4 #cj4 #hh ,abstr4 ,chem4 ,soc4 #aiab1 #ajb1 ii4 #aaha4 ,thorianite occurs in jet-black crystals with a bright resinous lustre4 ,they are pseudocubic1 and the twinning resembles that of the cubic mineral fluorspar--interpenetrant cubes1 twin axis a cube diagonal4 ,close examination shows1 however1 that twinning can only take place about one of the four diagonals1 and an optical examination makes it clear that the symmetry is really rhombohedral4 ,the case is exactly analogous to that of the mineral chabazite1 a zeolite which occurs in rhombohedra of which the angles differ but little from those of the cube1 and which also forms the interpenetrant twins4 ,in view of the fact that both uranous oxide and thoria have been obtained as octahedra1 whilst a fused mixture of the two on cooling forms cubic crystals1 it seems not unlikely that at high temperatures the pseudocubic thorianite would become truly cubic2 but no experiments in this direction seem to have been tried4 ,the crystals are brittle2 hardness #g2 sp4 gr4 #hj-ig4 ,thorianite is infusible1 incandescing before the blowpipe4 ,when powdered1 it dissolves readily in nitric and sulphuric acids1 with evolution of helium4 ,gray#hi has shown that the helium content can be reduced by #bh per cent4 by fine grinding1 thus showing that part at least of the gas must be mechanically held4 #hi ,proc4 ,roy4 ,soc4 #aijh1 ,a1 #hb1 #cjf4 ,thorianite was found in ,ceylon1 being originally mistaken for pitchblende4 ,a sample was supplied by the discoverer1 ,mr4 ,holland1 to the officers of the ,mineral ,survey1 by whom it was sent to ,london for examination4 ,its composition was determined by ,dunstan1 who named it4 ,it was found in the river gravels 7gem-gravels71 the matrix being a pegmatite granite4 ,it is a valuable source of thorium nitrate for incandescent mantles1 one ton of the mineral 7with thoria content of #gj per cent47 having been sold for #aejj2 but the supply is small and unreliable4 ,baddeleyite4#ij-- ,baddeleyite consists of almost pure zirconia 7,zr,o #ife per cent47 with small quantities of ferric oxide1 alumina1 lime1 magnesia1 alkalies and silica4 ,thoria and rare earths are present in traces1 uranium is absent2 the mineral is not radioactive1 and contains only traces of helium4 #ij ,vide ,fletcher1 ,min4 ,mag4 #ahic1 #df1 #aj1 #adh2 ,hussak1 ,zeitsch4 ,kryst4 ,min4 #ahie1 #bd1 #afd1 and #be1 #bih4 ,monoclinic--a 3 b 3 c #jihga 3 #a 3 #jeaad4 #ih #de4 ,common forms--all three pinakoids1 a #ajj1 b #jaj1 and c #jja1 with the hemi-prisms m #aaj1 k #abj1 and l #bcj1 and various pyramids and domes4 ,angles--7#ajj7 7#aaj7 #dd #ag2 7#ajj7 7#jja7 #ha #ad2 7#ajj7 7#aja7 #ee #cc4 ,cleavage c and b1 parting m due to repeated twinning4 ,twinning is exceedingly common2 of many hundred crystals examined by ,hussak1 only three were found untwinned4 ,twin planes m 7#aaj71 a 7#ajj71 and x 7#bja74 ,colour brown1 varying in zones by twinning1 with distinct pleochroism4 ,hardness2 sp4 gr4 varies from #dd to #fj1 being about #ee to #ef for fairly pure material4 ,double refraction negative1 #b ,e #gj-ge4 ,acute bisectrix nearly coincident with c axis1 plane of the optic axes b1 7#jaj74 ,the mineral is insoluble in acids1 readily soluble in fused potassium hydrogen sulphate4 ,before the blowpipe it is almost infusible2 it dissolves in the fused borax bead1 rapid cooling causing separation of crystals4 ,if a bead containing zirconia be heated until the borax is partially volatilised1 zirconia crystallises on cooling in tetragonal crystals1 isomorphous with those of rutile4#ia #ia ,nordenskild1 ,pogg4 ,ann4 #ahfa1 #aad1 #fbe2 for tetragonal zirconia see also ,troost and ,ouvrard1 ,compt4 rend4 #ahhh1 #ajb1 #adbb4 ,the mineral was discovered in #ahib by ,hussak and ,l4 ,fletcher independently4 ,the former1 who obtained it from the pyroxenite sand of ,so ,paulo1 ,south ,brazil1 believed it to be a tantalo-columbate1 and called it ,brasilite4 ,fletcher found it in a gem-gravel from ,rakwana1 ,ceylon1 and named it ,baddeleyite4 ,an analysis by ,blomstrand of ,hussak's mineral showed it to be identical with the ,ceylon mineral1 and ,hussak withdrew his name and accepted ,fletcher's4 ,it has recently been found#ib in a corundum-syenite1 near ,bozeman1 ,montana1 ,u4,s4,a4 #ib ,rogers1 ,amer4 ,j4 ,sci4 #aiab1 iv41 #cc1 #ed4 ,the mineral now comes on the market in commercial quantities2 pure zirconia almost entirely free from iron can be obtained by leaching with acids4 ,the pure oxide is extraordinarily refractory1 and promises to be of great use for crucibles1 furnace linings1 etc4 7vide p4 #cbd74 ,rutile4--,titanium dioxide1 ,ti,o1 occurs crystallised in nature in the three minerals ,rutile1 ,brookite1 and ,anatase 7,octahedrite71 which therefore form a trimorphous series4 ,they are all stable minerals1 though rutile appears the most stable1 being occasionally found in pseudomorphs after the other two4 ,the family is remarkable in that it is not unusual to find two of them occurring together--an uncommon phenomenon with polymorphous minerals4 ,rutile often contains small quantities of iron and chromium4 ,the ferriferous varieties are distinguished as ,nigrine1 which is black1 with #b-c per cent4 ferric oxide1 and ,ilmenorutile1 with up to #aj per cent4 of ferric oxide1 and specific gravity up to #eac4 ,crystal system--tetragonal1 holosymmetric2 c #jfddb2 7#jja7 7#aja7 #cb #dg4 ,common forms--prisms a #ajj1 m #aaj1 and l #caj2 pyramids e #aja1 s #aaa1 and many others4 ,the basal pinakoid c #jja is very rare4 ,habit1 prismatic1 with vertical striations2 or in slender needles4 ,twinning very common and varied2 usually on the cassiterite law--twin plane e 7#aja7--;forming the knee-shaped twins1 and irregular rosettes by repetition1 and many contact twins4 ,contact twins on the law--twin plane v 7#cja7 are less common4 ,cleavage a 7#ajj7 and m 7#aaj71 distinct4 ,hardness #f-f2 sp4 gr4 #dah-dbe1 and up to #eb if much iron is present4 ,colour reddish-brown to black1 with good metallic lustre2 transparent to opaque4 ,the refraction and double refraction are very high-- #bfaeh1 #bijbi for sodium light--and allow the crystals to be readily distinguished in rock-sections4 ,the mineral is insoluble in acids1 but can be dissolved after fusion with alkalies or alkali carbonates4 ,rutile is a member of the isomorphous series1 cassiterite1 zircon1 etc4 7see under ,thorite71 and in particular it has the colour1 appearance1 and twinning of cassiterite1 from which1 however1 it is readily distinguished by its lower specific gravity4 ,in this connection it is interesting to note that an apparently pure specimen1 quite free from inclusions1 was found 7#aijd7 to contain #ag per cent4 of tin dioxide4#ic #ic ,friedel et ,grandjean1 ,bull4 ,soc4 franc4 ,min4 #aiji1 #cb1 #eb4 ,as an accessory rock mineral1 and also as an important constituent of many sands1 rutile is of very wide distribution4 ,it occurs1 usually imbedded in quartz or felspar1 in many granites1 syenites1 gneisses1 slates1 and allied rocks2 in acicular crystals penetrating quartz it forms the #8,veneris ,crinis' of ,pliny4 ,at ,risr and other localities in ,norway1 it is found in the massive form1 and it is largely worked at ,risr as a source of titanium4 ,it occurs in all the countries of ,europe1 and largely in ,america4 ,arendal1 ,krager1 and ,risr1 in ,norway1 the ,binnenthal1 the ,urals1 the ,st4 ,gothard1 ,castile1 ,magnet ,cove in ,arkansas1 ,alexander ,co4 in ,n4 ,carolina1 ,barre and ,shelburne in ,massachusetts1 and ,chester ,co4 in ,pennsylvania are the chief localities4 ,it was in this mineral that the element titanium was first recognised by ,klaproth 7#agie74 ,anatase 7,octahedrite7 is the second crystalline modification of titanium dioxide4 ,tetragonal c #aggga4 7#jja7 7#aja7 #fj #ch1 7#aaa7 7#aaa7 #hb #i4 ,common forms--,prisms a #ajj and m #aaj1 pyramids p #aaa1 e #aja1 and many other complex forms2 the basal plane c #jja is occasionally found4 ,habit usually octahedral1 with p or v prominent2 sometimes tabular with c1 more rarely prismatic with a well developed4 ,cleavage c and p perfect4 ,hardness #e-f2 sp4 gr4 #chb-cie1 usually increasing after heating4 ,lustre adamantine1 so splendent that in ,brazil detached crystals have been mistaken for diamonds4 ,colour1 some shade of bluish-black to brown2 by transmitted light1 greenish-yellow4 ,transparent to opaque4 ,double refraction negative1 strong2 for sodium light #beed1 #bdic4 ,it is found at ,bourg d',oisans in ,dauphin1 and in ,norway1 the ,urals1 ,brazil1 etc4 ,in ,switzerland it occurs as the variety ,wiserine1 which was at one time believed to be xenotime4 ,it was named ,octahedrite by de ,saussure1 in #agif1 from the prevailing habit1 and ,oisanite1 from its occurrence in ,dauphin1 by ,delamtherie1 in #agig4 ,the name anatase 7 erection7 was proposed by ,hay1 being intended to denote that the vertical axis 7c 3 a7 is greater than that of rutile1 the other tetragonal modification of the dioxide4 ,brookite1 the third form of this compound1 is orthorhombic4 a 3 b 3 c #jhdaf 3 #a 3 #jiddd4 ,common forms--the three pinakoids a #ajj1 b #jaj1 and c #jja1 prisms m #aaj1 l #baj1 pyramids e #abb1 z #abb1 and numerous others4 ,angles--7#ajj7 7#aaj7 #dj #e2 7#jja7 7#ajj7 #dh #ah2 7#jja7 7#jaa7 #dc #bb4 ,the habit is varied2 it occurs usually in bipyramids with e and m or prismatic with m1 a1 and terminating pyramids4 ,cleavage m indistinct1 c very poor4 ,hardness #e-f2 sp4 gr4 #chg-dja4 ,lustre metallic4 ,colour brown to reddish- and yellowish-brown and black4 ,the optical behaviour is interesting4 ,the acute bisectrix is perpendicular to a 7#ajj71 but while for red light the plane of the optic axes is 7#jja71 for blue it is 7#jaj72 for an intermediate light1 therefore 7 #eeej 71 the mineral appears uniaxial4 ,the chief localities are ,bourg d',oisans1 ,miask1 the ,st4 ,gothard1 the ,tyrol1 ,magnet ,cove in ,arkansas1 and ,tremadoc in ,wales4 ,titanium dioxide can be obtained crystalline by the action of steam on titanium tetrafluoride1 ,ti,f1 at high temperatures2 it is stated that by varying the temperature of the reaction1 any one of the three crystalline modifications can be obtained4 99 99 99 99 99 ,the only other minerals which need be mentioned in this class 7see list7 are3 ,zirkelite1 a complicated mixture of oxides1 in which thoria1 zirconia1 and titanium dioxide act as acidic oxides1 and ,mackintoshite1 a mixture of several oxides1 of which those of thorium and uranium are the most important4 7b7 ,,the ,,carbonates ,lanthanite1 ,hydrocerite4--,this mineral is a carbonate of ceria earths1 chiefly lanthana1 of the formula ,la7,,co71#i;,h,o4 ,orthorhombic2 a 3 b 3 c #jiebh 3 #a 3 #jijbc4 ,common forms--the pinakoids a #ajj and c #jja1 with m #aaj and o #aaa4 ,angles--7#ajj7 7#aaj7 #dc #cg2 7#jja7 7#aja7 #dc #bf2 7#jja7 7#jaa7 #db #c4 ,habit tabular1 parallel to c2 cleavage perfect1 c4 ,double refraction negative2 optic axis plane a 7#ajj74 ,usually amorphous1 being probably an alteration product of a mineral rich in lanthanum4 ,hardness #b2 sp4 gr4 #bf-bg4 ,colour white to yellowish-white1 usually opaque2 infusible before the blowpipe 7being converted to the oxide71 readily soluble in acids4 ,lanthanite occurs with cerite at ,bastns1 and at ,bethlehem1 ,pennsylvania4 ,morton#id states that he prepared a crystalline didymium carbonate in the laboratory1 of the formula ,di7,,co71#h;,h,o1 which was isomorphous with lanthanite2 he concluded that the latter had only eight instead of nine molecules of water4 #id ,see abstract in ,zeitsch4 ,kryst4 ,min4 #ahhf-hg1 #ab1 #eah4 ,parisite 7,synchisite71 and ,cordylite4--,parisite is a fluocarbonate of calcium and cerium metals2 ,cordylite is an analogous compound in which barium replaces calcium1 and is isomorphous with ,parisite4 ,the formula of ,parisite is ,ca,r,f7,,co71 where ,r cerium metals4 ,groth formulates this as 7,ca,f77,,rf7,r7,,co71 ,penfield and ,warren as 7,,rf7,ca7,,co71 whilst ,schilling gives ,ce7,,co71,ca,f4 ,analogous formul may be proposed for ,cordylite1 ,ba,r,f7,,co74 ,since the two minerals are very similar in crystallographic properties1 one description will be sufficient for both4 ,the following are ,dana's data for ,parisite3 ,hexagonal1 c #cbhia4 7#jjja7 7#ajaa7 #ge #ae4 ,forms are extremely numerous1 and have remarkably high indices4 ,among the simplest are the base c #jjja1 the prism m #ajaj1 pyramids q #ajab1 and h #aabb2 the other forms are chiefly rhombohedra and pyramids4 ,the usual habit is that of an acute double hexagonal pyramid1 with form o #bjba1 terminated by c4 ,cleavage c1 perfect4 ,it is brownish-yellow to red4 ,hardness #d2 sp4 gr4 #dcf4 ,the double refraction is strong1 positive4 ,soluble in hydrochloric acid with effervescence4 ,both minerals are characteristic pneumatolytic species of the riebeckite-girine rocks4 ,parisite was discovered by ,paris in the emerald mines of the ,muso valley1 ,colombia1 in #ahce1 and first correctly analysed by ,bunsen in #ahde4 ,before the blowpipe it glows1 remaining infusible 7the glow does not appear to have been investigated in this case74 ,cordylite was discovered by ,flink in #aijj1 in ,greenland4 ,it is yellow to brownish-yellow and colourless4 ,hardness #d2 sp4 gr4 #dca4 ,before the blowpipe it decrepitates1 and is infusible2 moistened with hydrochloric acid1 it gives the characteristic barium flame4 ,the so-called ,synchisite was discovered by ,nordenskild who correctly described it as ,parisite4 ,flink found it in ,greenland1 and announced it as a new species1 with the formula ,r,f,ca7,,co71 i4e4 the formula for parisite plus one molecule of calcium carbonate1 ,ca,c,o4 ,from its extraordinary resemblance to parisite in physical and crystallographic properties1 ,palache and ,warren#ie believe that the specimens selected by ,flink for analysis must have consisted1 in reality1 of parisite with admixed calcium carbonate4 ,this conclusion has now been confirmed by ,quercigh1 by a careful comparison of the optical properties4#if ,the minerals are usually found together1 the chief localities being ,s4 ,norway1 the gold districts of the ,urals1 ,narsarsuk in ,s4 ,greenland1 and ,montana1 ,u4,s4,a4 #ie ,amer4 ,j4 ,sci4 #aiaa1 iv41 #ca1 #ecc4 #if ,abstr4 ,chem4 ,soc4 #aiab1 #ajb1 ii4 #ggc4 99 99 99 99 99 ,the following rare earth carbonates are described in the alphabetical list3 ,ancylite1 a basic hydrated carbonate4 ,tengerite1 a hydrated carbonate formed by the weathering of gadolinite4 ,kischtimite1 a fluo-carbonate related to parisite4 ,bastnsite 7,harmatite7 and ,weibyite1 hydrated fluocarbonates of the cerium elements4 ,,chapter ,,vi ,,the ,,phosphates ,,and ,,halides 7a7 ,,the ,,phosphates ,monazite1 ,phosphocerite4--,monazite1 by far the most important1 commercially1 of all the rare earth minerals1 is essentially an orthophosphate of the ceria earths1 of the formula ,r,,po4#ig ,the yttria earths are usually present in small quantities4 ,silica and thoria1 in quantities varying from traces up to #f per cent4 of the former and from #a to #bj per cent4 of the latter1 are invariable constituents2 it is almost entirely to the percentage of thoria that the mineral owes its commercial value4 ,the following also are common constituents1 though usually in very small quantities only--stannic1 ferric and manganous oxides1 alumina1 lime1 magnesia1 zirconia and water4 ,helium was observed in it by ,tilden1 and by ,ramsay1 ,collie and ,travers4#ih ,boltwood#ii and ,zerban#ajj found uranium in it2 the latter attributed this to impurities1 the former regarded it as an essential constituent4 ,strutt#aja found uranium in a pure monazite4 ,haitinger and ,peters#ajb detected radium1 their result being confirmed by ,boltwood and ,strutt4 #ig ,for the composition of the earths in monazite1 see ,james1 ,j4 ,amer4 ,chem4 ,soc4 #aiac1 #ce1 #bce4 #ih ,trans4 ,chem4 ,soc4 #ahie1 #fg1 #fhd4 #ii ,phil4 ,mag4 #aije1 vi41 #i1 #eii4 #ajj ,ber4 #aije1 #ch1 #eeg4 #aja ,proc4 ,roy4 ,soc4 #aije1 ,a1 #gf1 #hh and #cab4 #ajb ,sitzungsb4 kaiserl4 ,akad4 ,wiss4 ,wien1 ,may1 #aijd4 ,monazite occurs in small crystals belonging to the monoclinic system4 a 3 b 3 c #jific 3 #a 3 #jibef1 #gf #bj4 ,these values vary slightly with different specimens4 ,common forms--,ortho- and clino-pinakoids a #ajj1 b #jaj1 hemi-prisms m #aaj1 and n #abj1 hemi-ortho-prisms w #aja and x #aja1 hemi-clino-prism e #jaa1 hemi-pyramid v #aaa1 etc42 the basal pinakoid c #jja is rare4 ,angles--a m #dc #ag1 c w #cg #h1 c e #da #eh4 ,habit tabular1 parallel to a1 needle-shaped by elongation parallel to b axis1 or prismatic by good development of v4 ,cleavage c1 perfect1 a1 distinct1 b1 difficult4 ,twin plane a 7#ajj74 ,birefringence moderate1 positive2 plane of optic axes perpendicular to b1 nearly parallel to a4 ,acute bisectrix inclined to c at angle of #a-d4 ,dispersion feeble1 4 ,brittle4 ,hardness #e-e2 sp4 gr4 #di-ec2 conchoidal fracture4 ,lustre resinous4 ,colour1 red to brown1 yellow1 yellowish- and greenish-brown4 ,transparent when pure2 more often translucent to opaque4 ,monazite is with difficulty soluble in acids2 before the blowpipe it is infusible2 when moistened with sulphuric acid it colours the flame greenish-blue4 ,the mineral often occurs massive1 yielding angular fragments1 but is most common in rolled grains4 ,it occurs in the gneiss of the ,carolinas and ,georgia1 and in sands derived from the gneiss1 in ,idaho and many of the ,pacific ,states2 in ,brazil1 at various localities in the provinces of ,minas ,geraes1 ,bahia1 ,espirito ,santo2 in ,queensland1 ,australia2 in ,madagascar2 in ,ceylon2 near ,travancore in ,india2 in the ,urals2 in ,scandinavia1 etc4 ,the deposits of commercial value will be treated more fully in the next chapter4 ,it is of wide distribution as an accessory constituent of granites1 diorites1 and gneisses4 ,monazite was first described1 under the name ,turnerite1 by ,lvy1#ajc in #ahbc2 the specimen was from the collection of the ,english chemist ,turner1 who thought it a variety of sphene 7titanite71 and was named after him at the suggestion of the mineralogist ,heuland4 ,the specimen was stated to have been found in ,dauphin1 but in spite of considerable examination of the question1 the precise locality is still unknown4 ,the resemblance between ,turnerite and the mineral later described as monazite 7 to be solitary7 was pointed out by ,dana in #ahff1 and confirmed by ,pisani1 #ahgg4 ,the name ,monazite was first used by ,breithaupt#ajd in describing a mineral found by ,menge 7#ahbf7 accompanying zircon in a granite from ,miask in the ,urals4 ,breithaupt concluded1 from the high specific gravity1 that the mineral contained a heavy metallic oxide4 ,it was again described as ,mengite by ,brooke#aje in #ahca4 ,it was re-discovered by ,shephard#ajf in ,south ,carolina in #ahcg1 and described by him under the name ,edwardsite1 a variety from ,connecticut being called ,eremite4 ,to ,shephard belongs the honour of having discovered its true nature2 after analysis he described it as a #8,basic ,sesquiphosphate of the ,protoxide of ,cerium1' giving the formula 7modern notation7 #c;,ce,o1#b,p,o1 and finding also zirconia1 alumina1 and silica in it 7his specimen was probably very impure74 ,gustav ,rose#ajg showed this to be identical with monazite in #ahdj4 ,in #ahdf ,whler described1 under the name ,cryptolite1 a variety of tetragonal habit closely resembling zircon4 ,this occurs at ,arendal in ,norway1 enclosed by apatite1 in the granite2 it may be obtained by treatment with dilute nitric acid1 which dissolves the apatite4 #ajc ,annals of ,philosophy1 #ahbc1 #ba1 #bda4 #ajd ,schweigg4 ,j4 #ahbi1 #ee1 #cj4 #aje ,phil ,mag4 #ahca1 ii41 #aj1 #aci4 #ajf ,amer4 ,j4 ,sci4 #ahcg1 #cb1 #afb4 #ajg ,pogg4 ,ann4 #ahdj1 #di1 #bbc4 ,the question of the manner in which the thorium is combined in monazite is of considerable importance1 in view of the fact that it is to this element that the mineral owes its commercial value4 ,the amount present varies from traces up to over #bj per cent41 but the usual value is between #e and #g per cent4 ,the first explanation of its presence was advanced by ,dunnington#ajh who suggested1 on the result of only one analysis1 that orangite 7,th,si,o7 was present mechanically mixed with the monazite4 ,penfield#aji supported this suggestion1 and stated that in three analyses of pure material he found the ratio of rare earths to phosphorus pentoxide and that of thoria to silica exactly equal to unity1 though the actual amounts of thoria varied considerably4 ,he also quotes an analysis made by ,rammelsberg in #ahgg1 in which no thoria was found1 to show that it is not an essential constituent4 ,in a microscopic examination he found dark resinous particles scattered throughout the section2 after moistening with hydrochloric acid1 warming1 and washing1 these dark spots became white1 and could be stained with fuchsine1 the monazite remaining unaffected throughout4 ,he concluded that these particles were thorite or orangite4 #ajh ,amer4 ,chem4 ,j4 #ahhb1 #d1 #ach4 #aji ,amer4 ,j4 ,sci4 #ahhb1 iii41 #bd1 #bej2 #ahhh1 #cf1 #cbb4 ,blomstrand#aaj disputed ,penfield's conclusions4 ,in twelve analyses of monazite from various parts of ,scandinavia he never once found either thoria or silica absent4 ,of these twelve analyses1 two give the ratio of thoria to silica1 ,th,o 3 ,si,o1 exactly unity1 in seven cases the ratio is not greater than #abe1 in five cases it varies considerably4 ,he summed up his results in three statements3 7a7 ,silica is never absent2 its amount depends not on the amount of thoria1 but on the amount of phosphorus pentoxide present4 7b7 ,the thoria which is always present is combined partly with silica1 partly with phosphorus pentoxide4 7c7 ,in most cases1 the rare earths alone are insufficient to satisfy the ratio ,r,o 3 ,p,o #a4 #aaj ,j4 pr4 ,chem4 #ahij1 #da1 #bff4 ,an exhaustive examination of the question has been made more recently by ,kress and ,metzger4#aaa ,they made in all over fifty analyses1 using thirty different specimens of monazite2 they estimated silica both as quartz and as silicate silica1 and determined thorium by the fumarate method--the other investigators had used the thiosulphate method of ,hermann 7vide p4 #bhf74 ,their results may be summarised as follows3 7i47 ,silica is always present4 7ii47 ,the amount of silica usually increases with the thoria1 but not regularly4 7iii47 ,by far the majority of cases showed insufficient total silica to combine with the thoria present4 7iv47 ,in about #i per cent4 of the cases1 the thoria present was insufficient to combine with the silicate silica1 from which it follows that some foreign silicate must be at least occasionally present4 7v47 ,a careful microscopic examination showed conclusively that no thorite 7,th,si,o7 was present1 the silicate being biaxial2 quartz is present as such4 #aaa ,j4 ,amer4 ,chem4 ,soc4 #aiji1 #ca1 #fdj4 ,they conclude that thorium is present as phosphate1 and is an essential constituent1 but that there is always some admixed silicate1 most probably a felspar4 ,xenotime4--,chemically this mineral is closely allied to monazite1 being an orthophosphate of rare earths1 containing silica and thoria2 whereas1 however1 in monazite the content of yttria earths does not rise above #d per cent41 in xenotime these constitute by far the greater part of the bases1 the content of ceria earths ranging from #hb to #aa per cent4 ,the yttria earths1 chiefly oxides of yttrium and the erbium group1 vary from #eda to #fdg per cent4 ,there are traces of zirconia2 ,ramsay1 ,collie and ,travers detected helium1 whilst ,boltwood1 and also ,strutt1 found uranium and radium4 ,it also appears to contain traces of sulphuric anhydride4 ,the crystals are tetragonal1 holosymmetric4 c #jfahg2 7#jja7 7#aja7 #ca #de4 ,common forms are the prisms a #ajj and m #aaj1 the basal pinakoid c #jja1 the pyramids e #aja1 f #bja1 z #aaa1 etc4 ,cleavage m1 perfect4 ,uniaxial1 double refraction strong1 positive4 ,transparent to opaque4 ,colour1 brown to reddish-brown and yellow4 ,hardness #d-e2 sp4 gr4 #dde-def4 ,it is insoluble in acids1 and infusible before the blowpipe2 when moistened with sulphuric acid1 however1 it turns the flame bluish-green1 like most mineral phosphates 7vide monazite74 ,it is not so widely distributed as monazite1 but is not uncommon4 ,it often occurs with zircon--to which it is very closely allied in crystal form1 if the two are not actually isomorphous--in parallel growth1 in granitic rocks4 ,the diamond sands of ,diamantina1 ,brazil1 form the richest source of the mineral1 but it is also found in ,scandinavia1 at ,hitter1 ro1 etc4 ,the mineral is of considerable importance1 chemically1 on account of the high percentage of erbia earths4 ,in the works of ,bauer1 ,rosenbusch1 ,weinschenk1 ,schilling and ,iddings will be found accounts of a mineral named #8,hussakite4' ,these accounts rested on the work of ,kraus and ,reitinger1#aab who in #aija announced the discovery of a new species4 ,the crystals were obtained as a specimen of xenotime by ,prof4 ,muthmann from ,dr4 ,e4 ,hussak1 in ,so ,paulo1 and had the crystallographic properties of that mineral4 ,on analysis1 the amount of sulphur trioxide present was found to be remarkably high 7#fc per cent471 and ,kraus and ,reitinger concluded that the substance was distinct from xenotime4 ,they announced it as a new mineral1 with the name ,hussakite1 and the formula #c,r,o1#c,p,o1,,so or #f,,rpo1,,so1 and stated that by the action of dilute alkalies the sulphur trioxide could be easily and completely removed4 ,they therefore regarded xenotime as a pseudomorph#aac after hussakite1 the sulphur trioxide having been removed from the latter by the action of the alkaline waters of the earth's crust4 ,in support of this view1 they gave analyses of opaque crystals from a ,bahia sand represented as containing #bf to #bg per cent4 of sulphur trioxide1 and so as being intermediate forms produced during the change4 #aab ,zeitsch4 ,kryst4 ,min4 #aija1 #cd1 #bfh4 #aac ,one mineral is said to be pseudomorphous after another when the first is produced from the second by a chemical change which proceeds so slowly that the original structure and crystalline form are unaltered 7i4e4 a change proceeding molecule by molecule74 ,the pseudomorph is usually opaque and shows clear signs of the alteration4 ,the latter conclusion was quickly challenged by ,brgger1 who found no sulphur trioxide in a perfectly fresh and transparent xenotime from ro in ,scandinavia4 ,brgger concluded that the ,hussakite of ,kraus and ,reitinger was an independent species of the formula #e,,ypo17,,yso7,,po1 and that xenotime was not derived from it4 ,basing his work on the barium chloride test given by ,kraus and ,reitinger 7see below7 ,rsler#aad declared that #8,hussakite' was a common accessory constituent of igneous rocks1 having been previously mistaken for zircon1 which it resembles in appearance and optical properties4 #aad ,zeitsch4 ,kryst4 ,min4 #aijb1 #cf1 #beh4 ,in #aijg ,hussak#aae published a paper in which he showed that the mineral named after him was not a new species at all1 but a xenotime of prismatic habit4 ,analyses made at his request by ,florence in ,brazil1 ,g4 ,t4 ,prior in ,london1 and ,tschernik in ,st4 ,petersburg1 confirmed the original values given by ,gorceix 7sulphur trioxide up to #jbe per cent474 ,he mentions ,brgger's analysis of the ,norwegian specimen in which ,kraus and ,reitinger had found #b-c per cent4 of sulphur trioxide1 but in which ,brgger found none4 ,he explains the results of ,kraus and ,reitinger as due to the addition of barium chloride to the acidified solution of the carbonate fusion of the mineral1 by which barium phosphate was precipitated2 this was dried and weighed as barium sulphate4 ,rsler's tests are declared doubtful2 xenotime is not a widely spread rock constituent1 the mineral in question being really zircon4 #aae ,centr4 ,min4 #aijg1 #ecc4 ,in face of these results1 there can be little doubt that the name #8hussakite' is unnecessary and undesirable1 since the mineral to which it was applied is proved to be xenotime4 99 99 99 99 99 ,in the alphabetical list1 particulars of the following rare earth phosphates will be found3 ,castelnaudite1 a variety of xenotime containing zirconia4 ,churchite and ,rhabdophane 7,scovillite71 hydrated phosphates4 ,gorceixite1 an alumino-phosphate of alkaline and ceria earths4 ,retzian1 an hydrated arsenate of manganese1 calcium and rare earth metals4 7b7 ,,the ,,halides ,yttrocerite4--,this mineral is a fluoride of calcium and rare earth metals1 with water4 ,a recent analysis by ,tschernik#aaf gives the formula ,ce,f1#b,y,f1#i;,ca,f1#b;,h,o4 ,putting the rare earth metals together1 this gives #f,,rf1#i;,ca,f1#b;,h,o1 or ,r,ca,f1,h,o4 ,yttrocerite is of interest since it was probably in the analysis of this mineral by the discoverers1 ,berzelius and ,gahn1 that the double sulphate method of separating the yttria from the ceria earths was first employed#aag 7vide p4 #aef74 #aaf ,abstr4 ,chem4 ,soc4 #aijg1 #ib1 ii4 #cfb4 #aag ,schweigg4 ,j4 #ahaf1 #af1 #bdd4 ,it is found only massive or granular4 ,colour usually white to violet-blue1 sometimes reddish-brown4 ,hardness #d2 sp4 gr4 #cde4 ,infusible1 but loses colour before the blowpipe4 ,when powdered1 it dissolves completely in boiling hydrochloric acid1 and readily in sulphuric acid with evolution of heat4 ,it has been found at various localities in ,scandinavia4 ,yttrofluorite4#aah--,this is a fluoride of varying composition1 very similar to yttrocerite1 but characterised by the absence of water1 and the very small ceria content 7#ag per cent474 ,it is thus a fluoride of calcium and the yttrium metals4 #aah ,t4 ,vogt1 ,centr4 ,min4 #aiaa1 #cgc4 ,cubic1 with poor octahedral cleavage4 ,colour1 yellow to brown and yellowish-green2 transparent to translucent1 bleached by weathering4 ,very brittle4 ,hardness #d2 sp4 gr4 #ced-cef4 ,it is very similar to fluorspar 7except that the octahedral cleavage of the latter is very good71 and is regarded by ,vogt as an isomorphous mixture of the latter with yttrium fluoride 7or with a double yttrium calcium fluoride1 which is less probable74 ,this view would account for the variations in composition1 and also for the remarkable frequency with which traces of rare earths are found in fluorspar 7vide p4 #b74 ,yttrocerite is regarded as a similar isomorphous mixture1 but containing cerium metals in addition to the yttrium group4 ,yttrofluorite occurs in pegmatite veins in granite in ,northern ,norway1 with gadolinite1 fergusonite1 allanite1 fluorspar1 and the usual vein minerals4 99 99 99 99 99 ,the other members of this family 7see list7 are3 ,fluocerite1 a basic fluoride of yttrium and cerium metals4 ,tysonite1 a hydrated fluoride containing carbonates4 ,it is to be noticed that fluorine is the only member of the halogen family which occurs in nature in combination with rare earth elements4 ,this fact is possibly connected with the great age of the rare earth minerals1 and their formation during pneumatolytic metamorphism of plutonic rocks 7vide ,chapter ,i74 ,,chapter ,,vii ,,the ,,monazite ,,sands ,it has been stated that monazite is a not uncommon accessory constituent of many rocks1 particularly of granites1 gneisses1 diorites1 etc4 ,the crystalline material1 of which an account has been given1 is found sometimes in veins in these rocks1 more often in tiny crystals disseminated throughout the mass4 ,most of these monazite-bearing rocks are extremely old1 belonging to the ,archan or pre-,cambrian age1 and probably none are of secondary 7,mesozoic7 or later age4 ,it follows1 then1 that they have been subjected to erosion during practically the whole immense period of which geology can give us any detailed knowledge4 ,heat1 frost1 wind1 the action of vegetation and of percolating water1 the innumerable weathering agents known to the geologist1 have been at work on them during countless ages1 breaking1 crushing1 dissolving2 rains1 brooks1 rivers1 even ocean-waves have dissolved or washed away the fragments1 sorted them out unerringly according to density1 and re-deposited them1 now in a river-bed1 now at the base of some sea cliff1 now in a wide alluvial plain from which the water has long since retired4 ,it is in deposits of this nature that the monazite has been concentrated4 ,its relatively high specific gravity 7about #ej7 has secured its separation from the lighter mica1 quartz1 and felspar of the parent-rock2 but the heavier vein or accessory minerals have1 of course1 been concentrated with it4 ,zircon is an invariable constituent of these #8monazite sands1' as such deposits are called2 and others almost as frequently found are rutile1 ilmenite1 sphene 7titanite71 and apatite4 ,common1 too1 are the characteristic minerals of the metamorphic rocks1 garnet1 epidote1 sillimanite1 tourmaline1 etc4 ,rare earth minerals found in the monazite sands include xenotime1 fergusonite1 samarskite1 gadolinite1 and allanite4 ,the remaining minerals are oxides of iron and tin1 with1 of course1 a considerable amount of quartz4 ,it is apparent1 from what has been said above1 that monazite will be concentrated with the heaviest constituents of the rocks from which it is derived4 ,very often1 indeed usually1 these rocks are precisely those in which gold occurs1 disseminated sometimes in tiny particles1 sometimes collected into nuggets in veins of quartz and pegmatitic minerals4 ,the erosion of these rocks concentrates the gold with the heaviest minerals2 and hence it happens that monazite is an almost universal constituent of the gold- and gem-bearing sands and gravels4 ,in the ,carolinas and in ,brazil1 monazite is found in the gold washings2 and though in the past the two have always been extracted separately1 the gold first and the monazite from the washings or tailings1 there appears to be no reason why a system calculated to extract both--where1 of course1 the content is high enough--should not be put into operation in the future4 ,a chemical test affords the only reliable method of detecting monazite in a sand4 ,a little of the sand is washed with water to remove the lighter minerals and warmed with concentrated sulphuric acid4 ,a few drops of the liquid are poured off1 evaporated to small bulk1 and one drop placed on a glass plate4 ,this is placed under a microscope and one drop of a concentrated solution of sodium acetate is added4 ,if monazite is present in the sand1 tiny pointed oval crystals of sodium cerium sulphate will separate4 ,on the commercial scale1 monazite is extracted from the sands only1 in the manner described below4 ,an effort was made in ,north ,carolina in #aijf by the ,british ,monazite ,company1 representing the ,south ,metropolitan ,gas ,light ,company of ,london1 to extract monazite from the rock in which it occurs disseminated4 ,the rock was crushed and powdered1 and the monazite separated by washing off the lighter particles on concentration tables 7see below74 ,in the same year1 however1 the price of thorium nitrate was suddenly lowered #ej per cent4 by the ,german ,thorium ,syndicate1 which largely controls the ,brazilian output of monazite1 and the ,british company stopped operations in #aijg4 ,at present it may be said that only the sands are available for profitable extraction4 ,up to #ahie1 the ,carolina deposits1 which were worked chiefly by the ,welsbach ,light ,company of ,new ,york1 either directly or indirectly1 supplied all the demand1 but in that year the ,brazilian sands were first worked1 and a keen struggle commenced for the market4 ,the ,american companies1 after keeping up a considerable output for some years1 were forced to suspend operations in ,may #aiaj4 ,the ,brazil deposits1 worked by the ,german ,thorium ,syndicate and the ,austrian ,welsbach ,company1 which have an agreement1 now meet practically the whole demand4 ,the ,brazilian sand occurs chiefly along the shores of the southern provinces1 having been concentrated by the action of the tides from the products of erosion of the cliffs2 it is very uniform and considerably richer than the ,carolina sand1 and owing to its occurrence on the sea-shore1 the cost of transporting it is very low4 ,it is exported chiefly to ,germany1 recently also to the ,united ,states1 and to a small extent lately to ,england4 ,the method of working it is similar to that employed in ,carolina--namely1 concentration by washing and magnetic separation4 ,,the ,,north ,,american ,,deposits#aai #aai ,see ,nitze1 ,bull4 ,no4 #i1 ,n4 ,carolina ,geol4 ,survey1 #ahie2 also ,test1 ,colorado ,school of ,mines ,bull4 ,vol4 ,,iv4 ,no4 #b1 p4 #abe1 ,jan4 #aijh4 ,there are two important regions in ,north ,america within which monazite sands occur2 one extends over the ,carolinas1 and the north-western part of ,georgia1 the other over the ,idaho basin and neighbouring counties of the ,pacific ,slope4 ,it will be best to treat these separately1 as the deposits are somewhat different in character4 7a7 ,the ,carolina ,deposits1 including the unimportant ,georgia deposits1 which belong to the same field1 occur over an area approaching #djjj square miles4 ,the area is occupied chiefly by the ,piedmont plateau1 which is drained by a number of streams rising in the ,south ,mountains1 an eastern outlier of the ,blue ,ridge2 it is in the basins and valleys of these streams1 particularly at the head-waters1 that the monazite is chiefly found4 ,the geology of the district is very complicated1#abj the rocks being very highly altered granites4 ,the chief bed is known as the ,carolina gneiss1 and includes several types of gneiss1 usually very much weathered4 ,the sands1 which average about #a per cent4 of monazite1 are worked in and near the stream beds2 they occur in the beds1 and in layers #a to #b feet in thickness a few feet below the surface of the surrounding soil4 #abj ,see ,sterret1 ,u4,s4 ,geol4 ,survey 7,minerals71 #aijf1 p4 #aaie4 ,concentration was formerly effected chiefly by a crude process of washing4 ,in this process the sand is thrown on to a sort of sieve1 fixed over the upper end of a long wooden trough1 by one workman2 a jet of water is directed on to the sieve1 washing the sand through it4 ,the heavier particles fall to the bottom of the trough1 whilst the lighter are washed right through4 ,a second workman continually turns over the sand left in the box and on the sieve2 at the end of a day's work the #8concentrate' is collected4 ,this averages from #ae to #gj per cent4 of monazite1 according to the nature and amount of the heavy minerals accompanying it in the sand4 ,the concentrate is dried either on rubber or oiled cloths in the sun1 or on an iron plate covering a trough in which a fire is lighted4 ,the iron minerals are then picked out by means of a magnet1 and the sand filled into sacks for transport4 ,before treatment for thorium nitrate1 the sand is at the present day further concentrated by powerful magnetic separators4 ,in a few cases the older method of concentration by hand-washing has been abandoned for machine concentration1 the ,wilfley table being sometimes employed4 ,the principle here is exactly the same1 the sand being fed into a hopper by means of a moving belt and thence on to a machine-shaken table from which running water constantly removes the particles1 sorting them according to their specific gravity4 ,further separation of the dried concentrate has been effected by three kinds of separators4#aba ,the first was of the ,edison1 or fall-and-deflection type2 in this the sand is allowed to flow in a thin vertical stream past a horizontal magnet1 which deflects the minerals containing iron2 these fall on one side of a partition1 the part richer in monazite on the other4 ,the second was an electrostatic machine2 the heated sand is borne on a moving belt underneath a rotating vulcanite cylinder1 excited by felt-covered rubbers2 the lighter particles are attracted to the cylinder1 and dropped on one side1 the heavier passing on4 ,neither of these machines is of much value in effecting concentration1 and neither is in general use4 #aba ,see ,pratt and ,sterrett1 ,trans4 ,amer4 ,inst4 ,min4 ,eng4 #aiji1 #dj1 #cac4 ,the third1 and by far the most efficient and most widely-used machine1 is known as the ,wetherill electro-magnetic separator4 ,it depends on the principle1 first applied by the ,american engineer ,wetherill1 that not only the iron minerals1 but a large number of other minerals may be attracted if the magnetic field be sufficiently strong4 ,in all types of this machine used in cleaning monazite concentrates1 four magnetic fields of increasing intensity are traversed by the sand2 the first removes magnetite1 ilmenite1 and the larger fragments of garnet2 the second removes all the remaining garnet and ilmenite2 the third removes the coarser1 and the fourth the finer monazite1 tailings of zircon1 rutile1 and silica passing on4 ,careful adjustment of the magnetic fields will readily give a #ig-ii per cent4 monazite4 ,two types of this machine are in common use4 ,in the first the magnetic fields are obtained by four successive electro-magnets1 arranged so that a broad horizontally-moving belt passes between the poles of each in succession4 ,the upper poles are ground down to a fine edge perpendicular to the direction of the belt1 to secure a more powerful field4 ,just beneath these edges1 and just above the broad belt are four rapidly driven horizontal belts moving at right angles to the first or main belt2 these carry off and deposit in separate bins the minerals attracted by their respective magnets4 ,this type is known as the ,rowand separator4 ,in the second type four horizontal belts are arranged in the form of descending steps1 as shown in the diagram 7,fig4 #b74 ,the magnets are placed at the end of each belt1 and within it4 ,the attracted mineral is held to its own belt1 whilst the remainder drops on to the next2 the attracted mineral falls into a bin as soon as its belt carries it out of the magnetic field4 ,the sand to be cleaned is fed on to the first belt by means of a hopper4 ,the almost pure monazite so obtained is now treated chemically for its thorium4 ,the processes proposed and in use are described in ,chapter ,,xviii4 ,illustration3 ,,fig4 #b4 ,as already stated1 the extraction of monazite in the ,united ,states has practically ceased2 but the processes outlined above1 which were first brought into use in the ,carolinas1 have been adopted for the treatment of the ,brazilian sands4 7b7 ,the ,idaho ,deposits4--,monazite was first observed in placer-gold deposits in the vicinity of ,boise city near the ,snake river4 ,this deposit was a gold-bearing sand derived from granite4 ,later the gold-bearing sands of ,oregon were also found to contain monazite2 these sands are rich in zircon1 and contain platinum and allied metals as well as gold4 ,the sands of the ,pacific slope are the so-called black sands1 derived from hornblende1 and augite-granites1 usually porphyritic1 which are much weathered at the surface4 ,the soil is loose and is largely composed of granite fragments2 the rain and streams constantly bring it down to the valleys1 and continually renew the deposits4 ,the concentrates obtained by washing are rich in well-crystallised zircon1 with titanite and garnet4 ,in #aijf a company was formed to extract monazite from the black sand residues left after the extraction of gold4 ,by #aiji they had erected plant and commenced operations at ,centerville1 and proposed to work the poorer auriferous sands for gold during the monazite washing4 ,this1 it was expected1 could be done by washing the sands in boxes lined with amalgamated copper plates1 which would retain the gold4 ,considerable amounts of monazite had already been extracted from the tailings when a disastrous fire put a stop to the operations in #aiaj4 ,since then the production of monazite in the ,united ,states has practically ceased4 ,,the ,,brazilian ,,deposits ,brazil first became a serious competitor in the world's market with the ,united ,states1 for the supply of monazite1 in #ahie4 ,the greater percentage of thorium1 the more even quality of the sands1 and above all the occurrence on the sea-coast1 rendered the ,brazilian monazite cheaper from the beginning1 so that it soon ousted the ,carolina sand1 and since #aiaj has supplied the whole demand4 ,the deposits at present worked lie along the coasts of ,bahia1 ,minas ,geraes and ,espirito ,santo1 and whilst they are very rich in monazite1 there is the disadvantage that their position and extent1 and so also the possibility of working them1 depend very largely on the variations in the tides1 etc4 ,the largest of these deposits is on the shores of a bay near the island of ,alcobaca1 on the southern coast of ,bahia4 ,monazite also occurs to a considerable extent in the diamond sands and gold-bearing sands of many of the interior provinces4 ,in ,minas ,geraes it has long been known to occur at the celebrated mining centres of ,diamantina and ,ouro ,preto1 where xenotime and other rare earth minerals are also found2 it is also known at various localities in the surrounding mining provinces of ,so ,paulo1 ,goyaz1 and ,matto ,grosso4 ,more recently1 extensive inland deposits have been found by ,freise1 in the province of ,espirito ,santo4#abb ,in the plateau-basin of the ,muriah and ,pomba rivers he found a sand known locally as #8catalco' which carries an average of #ba per cent4 of monazite and a gold-content of #age grams per ton4 ,in the ,aymor's mountains he found monazite1 both massive and granular1 in pegmatite veins in granite2 analysis showed a thoria content of #ibc per cent41 which is very high4 ,these deposits would form a very valuable and extensive source of thoria1 if the difficulties of transport could be overcome4 #abb ,zeitsch4 pr4 ,geol4 #aiji1 #ag1 #ead2 ibid41 #aiaj1 #ah1 #adc4 ,at present1 as stated above1 only the beach deposits are worked4 ,the ,brazilian ,government has laid a very heavy tax on all monazite exported2 it is stated#abc that the ,german ,thorium ,syndicate pays #ej per cent4 of its profits in royalties to the ,government4 ,in spite of this1 the high quality of the sand and the low cost of transport have enabled this combine to lower the price of thorium nitrate to a point at which the ,carolina sands cannot be worked1 and it appears probable that the world's markets will be supplied for some time1 at least1 entirely from ,brazil4 ,the methods employed in working the sand are similar to those already described4 #abc ,u4,s4 ,geol4 ,survey 7,minerals71 #aijf1 p4 #aaie4 ,in the last few years monazite deposits have been found in various places1 notably in ,australia1 ,india1 and ,ceylon4 ,in the latter locality it occurs sparingly in the gem-gravels1 in association with the much more valuable thorianite and thorite1 but the supply is uncertain1 and the minerals cannot be worked regularly4 ,in ,australia it occurs in ,victoria and in ,queensland4 ,in ,victoria the deposits are poor in monazite--about #jjbe per cent4--so that working is not profitable4 ,in ,queensland it occurs in beach sands on the southern coast1 with gold1 platinum1 and cassiterite2 there seems to be no reason why these deposits should not be profitably worked when sufficient labour is forthcoming4 ,it also occurs in ,north ,queensland1 on the ,walsh and ,tinaroo mineral fields2 here it is found massive and granular in veins in granite1 associated with wolframite1 molybdenite1 and cassiterite4 ,quite recently1 deposits of considerable extent have been found near ,travancore1 ,india4#abd ,these sands contain about #df per cent4 of the mineral1 which is itself very rich in thoria1 containing about #aj per cent4 of the oxide2 the unconcentrated sand is therefore as valuable as a source of thorium nitrate as the ordinary ,brazilian concentrates1 which average #d per cent4 or less of the oxide4 #abd ,bull4 ,imp4 ,inst4 #aiaa1 vol4 ix41 ,no4 #b1 p4 #ajc4 ,monazite has also been observed in the tin-bearing sands of ,embabaan1 ,swaziland1 ,south ,africa1 and in the province of ,ottawa1 ,canada4 ,,chapter ,,viii ,,radioactivity ,,of ,,the ,,minerals ,in the present chapter no attempt will be made to give a complete account of all the phenomena of radioactivity which have been observed in the mineral world4 ,there are1 however1 a few problems of the highest scientific interest which centre about the rare earth minerals1 and mention of these can hardly be avoided in a work which professes to give a general account of the rare earth group4 ,it is obvious that a detailed treatment cannot be given without entering into phenomena which would be quite beyond the range of the present work1 and an excuse is hardly needed1 therefore1 for the fragmentary and abbreviated account which follows4 ,the reader's acquaintance with the general phenomena of radioactivity is of necessity assumed4 ,radioactivity 7the spontaneous emission of special radiations7 was first observed by ,becquerel1 in #ahif1 in the case of potassium uranyl sulphate1 and was soon found to be common to all uranium compounds1 and to the metal itself4 ,mme4 ,curie showed that whilst in uranium salts the degree of activity varies directly with the percentage of uranium1 in minerals containing the element the same rule does not hold4 ,the observation that pitchblende is considerably more active than the uranium it contains led to the discovery of polonium#abe and radium in #ahih4 ,exactly analogous phenomena were shown to hold for thorium salts and thorium-containing minerals by ,mme4 ,curie and ,schmidt in #ahih1 and in #aije ,hahn separated ,radio-thorium from thorianite4 ,in #ahii ,debierne discovered that the rare earths precipitated from the solution obtained on treatment of pitchblende are associated with another extremely active body1 which he named ,actinium2 ,giesel found that in the separation of the rare earths this remains with lanthanum4 ,in #aijc ,ramsay and ,soddy experimentally confirmed the prediction of ,rutherford and ,soddy1 that radium would be found to produce helium continuously4 ,the discovery of these remarkable phenomena has modified many fundamental physical conceptions1 and has opened up a new field of scientific enquiry1 which is being developed with unexampled rapidity4 #abe ,polonium1 which was named by ,mme4 ,curie in honour of her native country1 has been shown to be identical with ,marckwald's #8,radio-tellurium1' which was named by ,rutherford #8,radium ,f'2 it is one of the degradation products of radium4 ,it has been mentioned1 in the accounts of the rare earth minerals given above1 that almost all these minerals are radioactive1 i4e4 have the property of emitting specific radiations4 ,moreover1 radioactivity1 to any considerable extent at least1 is1 with a few important exceptions1 confined to the minerals which have been already described4 ,it has been shown by many investigators1 chief amongst whom are ,strutt and ,boltwood1 that the activity is usually due to the presence of uranium or thorium1 or both4#abf #abf ,hauser and ,wirth 7,ber4 #aiaj1 #dc1 #ahjg7 observed activity in some zirconium minerals containing neither thorium nor uranium4 ,after the discovery of helium in ,cleveite 7a variety of pitchblende1 vide p4 #ac7 in #ahie by ,ramsay1 a large number of minerals were examined for this gas1 and it was found that almost all the rare earth minerals contain helium4 ,the fact that these minerals are also for the most part radioactive1 naturally suggested some relation between the activity and the presence of helium1 and led directly to the discovery that radium is continuously producing helium2 and it became apparent that helium has been accumulating in these minerals since their formation1 by the decay of radioactive elements4 ,the question of the origin of helium in minerals will be touched on again4 ,in #aijd ,boltwood advanced the theory that radium is produced by the degradation of uranium1 the parent-element having1 however1 a much greater half-life period4 ,if uranium continuously produces radium1 whilst the latter decays much more rapidly than the former1 it must follow that in minerals containing uranium a state of equilibrium is reached between uranium and radium1 and the ratio of these two in all minerals should therefore be constant1 and independent of the geological age4 ,boltwood examined a number of the minerals of which descriptions have been given in the preceding chapters1 and found the ratio to be surprisingly constant4#abg ,strutt also examined a large number of minerals1#abh and whilst on the whole his results seemed to support the theory1 his values for the ratio were by no means so constant as those of ,boltwood4 ,strutt included in his examination the interesting radium-containing mineral observed by ,danne at ,issy l',evque4#abi ,this was a pyromorphite 7lead chlorophosphate7 containing neither uranium nor thorium4 ,danne suggested that the radium was not an original constituent1 but had been introduced by the action of percolating waters4 ,this view was confirmed by ,mc,coy and ,ross1#acj who found that the activity was entirely confined to the surface layer4 #abg ,amer4 ,j4 ,sci4 #aijd1 iv41 #ah1 #ig2 ,phil4 ,mag4 #aije1 iv41 #i1 #eii4 #abh ,proc4 ,roy4 ,soc4 #aije1 ,a1 #gf1 #hh and #cab4 ,ibid4 #aijg1 ,a1 #hj1 #ef4 #abi ,compt4 rend4 #aije1 #adj1 #bda4 #acj ,j4 ,amer4 ,chem4 ,soc4 #aijg1 #bi1 #afih4 ,mlle4 ,gleditsch has also examined the question of the uranium-radium ratio in minerals4 ,her earlier work#aca gave ratios which1 whilst constant for each mineral species1 varied in much the same manner as ,strutt's for different species1 and afforded very little support to ,boltwood's theory4 ,her more recent results1#acb however1 are much more closely in accord with the theory1 which has been still further strengthened by the work of ,pirret and ,soddy#acc and of ,marckwald and ,russell4#acd ,it may now be regarded as firmly established that radium is in the line of direct descent from uranium4 #aca ,compt4 rend4 #aiji1 #adi1 #bfg2 ,le ,radium1 #aiji1 #f1 #afe4 #acb ,le ,radium1 #aiaa1 #h1 #bef4 #acc ,phil4 ,mag4 #aiaa1 vi41 #ba1 #feb4 #acd ,ber4 #aiaa1 #dd1 #ggg4 ,boltwood had assumed that the helium in radioactive minerals is produced from the uranium1 during its disintegration4 ,strutt1 however1 disputed this2 his experiments showed that very little helium is found even in the richest radium-uranium minerals unless thorium is also present4 ,thus pitchblende contains a very high percentage of uranium1 but relatively little helium 7there is usually a considerable thorium percentage here too1 so that nothing conclusive can be deduced from this74 ,adams#ace found that carnotite1 a mineral very rich in uranium1 but containing no thorium1 contains no helium at all2 he explained its absence by the very loose texture and permeability of the mineral1 which would allow the gas to escape4 ,strutt concluded that whilst helium is undoubtedly produced by disintegration in the uranium series1 in minerals it is produced more by thorium or1 as more recent work indicates1 by radio-thorium1 than by uranium4 #ace ,amer4 ,j4 ,sci4 #aije1 iv41 #bj1 #bef4 ,the question of the origin of helium in minerals is1 however1 not definitely settled1 for several anomalous cases are known4 ,thus the yttria silicate1 ,thalnite 7q4v471 contains quantities of helium1 but no uranium or thorium is given in the analyses4 ,similarly1 ,risrite contains a relatively large quantity of helium1 but only traces of uranium and thorium4 ,in the last mineral1 the active constituent is precipitated with the lead1 so that no radio-thorium appears to be present4 ,further1 ,thomsen analysed a fluorspar from ,ivitgut in ,greenland which he found to contain #bg c4c4 of helium per kilogram4 ,this specimen contains no uranium1 but gives off the thorium emanation in quantities which suggest the presence of radio-thorium2 moderate quantities of thorium are also present4 ,since the particle has been definitely identified as a positively charged helium atom1 it appears certain that disintegration in all three series 7uranium1 actinium1 and thorium series7 produces helium1 and a mineral containing a member of any of these series 7which gives rays or ray-giving products7 would also contain helium4 ,even so1 there is a case in which the helium content is anomalous1 if not altogether beyond explanation at the present stage4 ,in examining a large number of minerals for helium1 ,strutt#acf found that some samples of beryl1 a beryllium aluminium silicate1 contain a relatively very large amount of helium1 but only traces of thorium1 and was altogether inactive4 ,the absence of any active constituent renders untenable the ordinary explanations of the presence of such a surprising quantity of helium4 ,boltwood has put forward a suggestion which in the present state of our knowledge must be regarded as a provisional explanation4 ,he conceives that in the concentration of beryllium from the parent magma1 it may have become associated with some short-lived intermediate radioactive element1 which had been altogether separated from its long-lived parent element in the process of concentration2 this intermediate element1 having collected in the crystallised beryl1 decayed completely in the course of the great period which must have elapsed1 leaving the helium to which it had given rise during its disintegration enclosed in the mineral4 ,it is difficult to see how two substances which must be so intimately connected as a parent-element and its product could be completely separated in the process of cooling of a magma2 but since so little is known of the process of crystallisation of minerals1 the suggestion can hardly be rejected on geological grounds4 ,in any case1 we have here only one strongly marked exception to the very definite rule that in all cases in which helium occurs in minerals1 it is accompanied by and undoubtedly produced from1 a radioactive element or elements2 and in the majority of cases1 the helium in minerals is produced by disintegration of uranium or thorium and their products4 #acf ,proc4 ,roy4 ,soc4 #aijh1 ,a1 #hj1 #egb4 ,strutt found that traces of helium are universal in the mineral world4 ,his method of determining helium was approximate only4 ,he obtained the gas content by heating the powdered mineral--a method which1 as ,wood has shown1#acg will only give all the gas when very high temperatures 7up to #ajjj;,c47 are employed4 ,the gases were freed from oxygen and hydrogen by passing over a heated1 partially oxidised1 copper spiral1 and from carbon dioxide by means of potash4 ,nitrogen was removed by sparking with excess of oxygen and shaking over potash2 the excess of oxygen was removed by melted phosphorus4 ,the inert gases so obtained were freed from all impurities by the use of the liquid alloy of sodium and potassium for the electrodes of the spectrum tube in which the gases were examined spectroscopically4#ach ,argon1 if present--it seems to be a universal constituent of igneous rocks1 into which it may have been absorbed from the air--was removed by charcoal at a temperature of -#hj;,c4 ,the helium so left was examined spectroscopically1 and measured in a ,mac,leod gauge4 #acg ,proc4 ,roy4 ,soc4 #aiaj1 ,a1 #hd1 #gj4 #ach ,as soon as the discharge is started in such a tube1 all the gases present other than those of the helium family are absorbed by these electrodes4 ,as stated1 helium was found in traces in nearly all minerals1 and its presence is to be attributed to traces of radium1 which also appears universal4 ,in minerals containing uranium or thorium1 or rare earths 7the latter are almost always accompanied by uranium and thorium71 helium is found to a much greater extent1 and ,ramsay considers it possible that some fraction of the helium content may arise from the rare earth metals4 ,there is1 however1 no positive evidence to support the conjecture4 ,he found that the helium ratio1 i4e4 the volume of helium per gram of uranous oxide1 ,,uo1 varies with the amount of thoria present2 but where the latter is absent the variations are much less marked4 ,if helium were produced in a mineral from uranium alone1 and none escaped1 it is obvious that the helium ratio would depend only on the age of the mineral4 ,for minerals of about the same age1 and containing no thorium1 the helium ratio would be roughly constant1 if no disturbing factor required consideration4 ,in #aije ,strutt pointed out that in all the minerals he had examined1 thorium was never present unless accompanied by uranium and radium1 whilst uranium and radium often occurred without thorium4 ,he suggested that the present atomic weight of thorium1 #bcbe1 was too low1 and that it was really the parent of uranium 7at4 weight #bche72 he further supposed that the next permanent member in the line of descent was one of the cerium metals4 ,these suggestions have been negatived by later work of ,boltwood and ,holmes4 ,the former pointed out#aci that it was far more likely that thorium is a disintegration product of uranium of considerably longer life4 ,on the whole1 however1 there is very little positive evidence to connect thorium with uranium4 #aci ,boltwood1 ,amer4 ,j4 ,sci4 #aije1 iv41 #bj1 #bef4 ,in the same year ,boltwood 7loc4 cit47 drew attention to the persistent appearance of traces of lead1 bismuth1 barium1 etc41 in the radioactive minerals1 and also pointed out that the variations of the ratio of helium to uranium in pitchblende might be used to determine the age of the mineral4 ,in #aijg he suggested#adj that lead was the final product of the degradation of uranium1 from which it follows that the ratio of uranium to lead should be constant for minerals of the same age 7since1 lead decays1 if at all1 at an infinitely slower rate than uranium74 ,he collected all the available analyses1 and classified the minerals dealt with into six groups according to the value of the ratio4 ,the order given by the ratio was declared to be in accordance with the order of age as given by geological evidence4 #adj ,amer4 ,j4 ,sci4 #aijg1 iv41 #bc1 #gg4 ,holmes#ada has further extended this work4 ,he examined a number of rare earth and allied minerals from the ,christiania district1 which ,brgger considers to be of approximately ,lower ,devonian age1 and found the ratio of lead to uranium to approximate quite closely1 for almost all the minerals examined1 to #jjde4 ,representing the change in the usual way as ,u #h;,he ,pb #bche #caib #bjga and using the data calculated by ,rutherford and others for the rates of decay1 he gives the age of ,lower ,devonian strata as about #cgj million years4 ,this figure is about twice as great as that deduced by palontologists from the flora and fauna1 and greater still than the times based on physical data1 e4g4 rates of cooling1 precession and nutation1 etc4 ,his figures for pre-,cambrian rocks1 based on the same ratio1 range between #ajjj and #afdj million years1 the later being deduced from a thorianite from the ,archan rocks of ,ceylon4 ,strutt's figure for ,archan rocks is about #gjj million years2 this was derived from work on the helium ratio1 which must now be considered4#adb #ada ,proc4 ,roy4 ,soc4 #aiaa1 ,a1 #he1 #bdh4 #adb ,see ,strutt1 ,proc4 ,roy4 ,soc4 #aijh1 ,a1 #hb1 #aff2 #aiji1 #hc1 #if2 #aiji1 #hc1 #bih2 #aiaj1 #hd1 #aid4 ,in #ahih ,travers#adc had examined the effect of heat on cleveite and fergusonite1 and found that about half the total helium1 together with hydrogen1 is given off at a bright red heat4 ,he considered it likely that the helium was combined with a metal 7though he recognised no distinction between occlusion and combination7 and remarked3 #8,the results of such experiments cannot therefore serve as a basis for speculation as to the origin or history of the substances in question4' ,the chemical inactivity of helium1 however1 as well as the experiments of ,moss and ,gray1 who showed that helium was evolved on grinding the materials1#add indicate that the gas is mechanically bound only4 ,this1 however1 introduces the difficulty1 if an attempt be made to use the helium-uranium ratio to calculate the age of minerals1 that the gas would be expected to escape from a porous material1 so that its amount is never so great as it should be4 ,strutt himself found that helium escapes rapidly from powdered monazite1 whilst even the solid mineral was found to evolve helium at a rate much in excess of the probable rate of production by radioactive changes4 ,similar results were found with thorianite1 and the only conclusion1 since helium is found in the minerals1 is that under the conditions under which these minerals exist in the earth's crust1 this escape is checked or altogether prevented4 ,it follows1 however1 that any age determined from the helium ratio must be a minimum age1 since there is always the chance of loss2 this of course is not the case--except where the minerals have suffered chemical changes--with the lead ratio1 and may account for the discrepancies observed4 #adc ,proc4 ,roy4 ,soc4 #ahih-ii1 #fd1 #adj4 #add ,vide ,gray1 ,proc4 ,roy4 ,soc4 #aijh1 ,a1 #hb1 #cjf4 ,strutt's earlier work on the helium ratio was made with phosphate minerals 7coprolites and fossil bones7 of known ages4 ,the ratios found were not in order of age1 the minerals being very permeable1 so that helium had probably been lost4 ,he next turned his attention to igneous rocks1 and selected zircon for the work4 ,here he obtained some sort of regularity in the order of age and the order given by the ratio1 and assumed that if helium were lost at all1 it must be lost in roughly proportional amounts by reason of the similarity in conditions4 ,geological criticism tends to lessen the trustworthiness of the conclusions2 it is pointed out that the age of a specimen of zircon is not necessarily that of the rock in which it occurs1 for zircon is an extremely stable mineral1 and might survive unchanged several fusions and re-crystallisations of the magma4 ,strutt replies to this that at the temperature of fusion of a rock1 zircon would certainly give up its accumulated helium1 so that the age determined from the helium content would be that of the last fusion1 i4e4 the age as given by geological data4 ,on the other hand1 our ignorance of the real mechanism of the crystallisation of a magma1 and especially of the amount and effect of the pressures obtaining1 robs this reply of its force1 and the objection must be counted valid4 ,in still later work ,strutt used sphene and thorianite1 and his results agree as well as can be expected4 ,the sphenes used were all from ,archan rocks1 except one1 which was from a ,tertiary volcanic deposit of the ,laacher ,see1 near ,coblenz 7the lake is in the crater of an extinct volcano74 ,in this case the helium ratio was very much smaller 7about of the values for ,archan rocks7 indicating the 7comparatively7 extremely recent formation of the deposit4 ,the most recent results in the study of radioactivity point to the conclusion that elements which differ in atomic weight and radioactive properties may be chemically identical1 or at least chemically inseparable2 such elements have been termed isotopes4 ,the end product of the thorium series of radio-elements should have an atomic weight of about #bjhd1 and it has been suggested that the element actually produced in this series of changes may be bismuth4 ,the latest results1 however1 rather point to the conclusion that disintegration in the thorium series gives rise to an isotope of lead4 ,if this hypothesis be true1 the lead derived from a mineral rich in thorium and poor in uranium should have an atomic weight appreciably higher than that of ordinary lead4 ,experiments to test this conclusion have recently been carried out by ,soddy and ,hyman4#ade #ade ,proc4 ,chem4 ,soc4 #aiad1 #cj1 #acd4 ,these authors have made analyses of ,ceylon thorite1 which they find to contain #jce per cent4 of lead2 from the ratio of thorium to uranium in the mineral1 they calculate that the lead should have an atomic weight of #bjhb1 that of ordinary lead being #bjga4 ,preliminary comparative experiments on #a gram of pure lead chloride extracted from the mineral point to an atomic weight for the thorite lead of #bjhd1 a result surprisingly in accord with theory4 ,more extended experiments on this most interesting question are in progress4 ,the present chapter would be incomplete without a reference to the interesting work of ,goldsmidt on radioactivity as an aid in identifying mineral species4#adf ,he describes a simple method by which the activity of a mineral may be rapidly and easily measured to a sufficient degree of approximation1 and shows how the determination enables a line to be drawn on a diagram already mapped out2 this line will intersect an area on the diagram which corresponds to the particular mineral4 ,owing to lack of analytical data1 and to the great difficulty of determining with accuracy small quantities of uranium and thorium1 the method is at present of scientific interest only2 but it is capable of development1 and its development would be of undoubted value in the further study of this branch of radioactivity4 #adf ,zeitsch4 ,kryst4 ,min4 #aijg-h1 #dd1 #ede2 ibid4 #aijh1 #de1 #dij4 ,in order to make this part of the subject as clear as possible1 the chief points in this chapter are summarised as follows3 #a4 ,radioactivity is only observed to an appreciable extent in some rather rare minerals4 ,these minerals as a rule contain radium1 uranium1 thorium1 rare earths1 and helium4 #b4 ,the helium has been produced during geological time by the degradation of one or more members of the three series of active elements 7the ,uranium1 ,actinium1 and ,thorium series74 #c4 ,radium is a degradation product of uranium1 and itself is degraded continuously2 the final product of degradation is probably lead4 #d4 ,the age of minerals has been calculated from the ratio of lead to uranium2 the figures obtained are much greater than those put forward by geologists and physicists4 #e4 ,the helium ratio has also been used1 but appears less trustworthy1 owing to escape of helium1 and uncertainty as to geological age of the minerals employed4 #f4 ,some connection between radioactivity and the presence of the yttrium or cerium metals appears highly probable1 but no satisfactory theories have been advanced on this point2 it has been shown that actinium is very closely allied to lanthanum4 ,,part ,,ii ,,the ,,chemistry ,,of ,,the ,,elements ,,chapter ,,ix ,,general ,,properties ,,of ,,the ,,cerium ,,and ,,yttrium ,,groups ,the chemistry of the rare earth elements begins in the year #agid1 with ,gadolin's discovery of the new oxide #8,ytterbia1' for which the name ,yttria was subsequently proposed by ,ekeberg1 and generally adopted 7see ,chapter ,i1 and under ,gadolinite1 p4 #ce74 ,the discovery of ,ceria followed in #ahjd 7see under ,cerite1 p4 #cb74 ,the classical work of ,mosander1 carried out between #ahch and #ahdb1 showed the complex nature of the new oxides4 ,from ceria he separated three new earths1 ,ceria proper1 ,lanthana1 and ,didymia4 ,yttria was shown to be a mixture of at least three oxides1 for which the names ,yttria1 ,erbia1 and ,terbia were proposed4 ,these oxides were believed to have the general formula ,,ro1 by analogy with the alkaline earths1 which they were found to resemble in many respects1 notably in their strongly basic character4 ,the properties of the new oxides were examined during the next twenty years by many chemists1 the chief workers being ,marignac1 ,rammelsberg1 and ,hermann1 but the next important advance was the investigation of the absorption spectra of solutions of the rare earth salts1 first suggested by ,gladstone in #ahef1 and developed more fully by ,bunsen and ,kirchhoff in #ahfj and the following few years4 ,the introduction of the methods of spectrum analysis furnished a very delicate and valuable method of examining and identifying the various oxides1 and so greatly assisted the laborious processes of separation4 ,sixteen elements 7excluding thorium and zirconium7 are at the present time recognised as belonging to the rare earth group4 ,with one or two exceptions1 these show the closest resemblance to one another1 both in chemical behaviour and in the properties of their compounds1 so that the difficulties of separating and purifying them are very great4 ,they may be said to form a series1 in which the properties vary continuously but gradually from member to member1 so that no sharp differences are anywhere perceptible4 ,the method of division into groups is1 therefore1 almost entirely one of convenience1 and has arisen from the course which the separations have followed4 ,the elements are divided into two chief families or groups1 that of the cerium metals and that of the yttrium metals respectively4 ,the cerium elements are separated by a process depending on the relative insolubility of their alkali double sulphates2 in this group are included cerium1 lanthanum1 praseodymium1 neodymium1 and samarium4 ,the yttrium family is further divided into four sub-groups3 the first consists of scandium and yttrium2 the second or terbium group of europium1 gadolinium1 and terbium2 the third or erbium group of dysprosium1 holmium1 erbium1 and thulium2 and the fourth or ytterbium group of ytterbium and lutecium--the element celtium1 recently discovered by ,urbain1 will also fall into this sub-group1 but the discovery awaits confirmation4 ,whilst scandium and yttrium fall into somewhat abnormal positions1 corresponding to their low atomic weights1 the terbium elements occupy an intermediate position between the cerium elements and the remaining yttrium elements1 or yttrium group proper1 and so are frequently classified as a third or intermediate group4 ,this list does not include all the names which have been put forward to designate what have been claimed from time to time as new elements2 whilst the individuality of some of those included is not yet fully established1 and the homogeneity of others has been called in question4 ,the uncertainty is more pronounced among the yttrium elements than among the cerium elements2 owing to the opportunities for investigation furnished by the commercial treatment of monazite1 the chemistry of the cerium group may be regarded as complete4 ,in the following table the elements are arranged in order of increasing atomic weight1 and it can be seen at once how closely the division into groups follows this order3 ,,element ,,atomic ,,wt4 ,,colour ,,of ,,salts ,scandium1 ,sc #dda ,colourless ,yttrium1 ,yt #hij ,colourless ,lanthanum1 ,la #acij ,colourless ,cerium1 ,ce #adjbe ,cerous1 colourless2 ceric1 ,cerium orange to red ,group4 ,praseodymium1 ,pr #adjf ,green ,neodymium1 ,nd #addc ,red to reddish-violet ,samarium1 ,sa #aejd ,topaz yellow ,terbium ,europium1 ,eu #aebj ,faint rose ,group4 ,gadolinium1 ,gd #aegc ,colourless ,terbium1 ,tb #aeib ,colourless ,dysprosium1 ,dy #afbe ,bright green ,erbium ,holmium1 ,ho #afce ,yellow to orange ,group4 ,erbium1 ,er #afgg ,deep rose ,thulium1 ,tm #afhe ,bluish-green ,ytterbium ,ytterbium1 ,yb #agbj ,colourless ,group4 ,lutecium1 ,lu #agdj ,colourless ,in their chemical relations1 the rare earth elements may be placed between the metals of the alkaline earths1 and the trivalent metals iron1 aluminium1 and chromium4 ,with the exceptions of cerium in the ceric salts1 and of samarium and europium in the recently discovered dichlorides1 they are uniformly trivalent1 but the oxides are very strong bases1 and the salts very slightly hydrolysed in dilute solutions2 generally1 therefore1 they resemble the calcium family rather than the aluminium group4 ,among the common salts1 the oxalates1 phosphates1 chromates1 iodates1 fluorides1 carbonates1 tartrates1 and borates are almost insoluble2 the sulphates are only sparingly soluble at ordinary temperatures4 ,among the double salts1 the alkali double sulphates are of great importance from their employment for separations2 the tendency to the formation of complex salts is greater among the yttrium than among the cerium elements1 increasing with the atomic weight1 and with the decrease in basic strength of the oxides4 ,the great similarity in chemical behaviour of the rare earth elements is apparent not only in the similarity in composition1 solubility and chemical properties of the salts--which is so great that the general account of the compounds which follows applies almost in its entirety to each member of the group--but also in the crystallographic relations between corresponding compounds4 ,many of the salt hydrates form isomorphous series2 the sulphate octohydrates1 for example1 appear to be isomorphous throughout the whole group1 and probably the relation would be found to apply even more completely than is generally accepted1 if the necessary data were forthcoming4 ,of great interest and practical importance is the isomorphism between the nitrates and double nitrates of the cerium elements and bismuth1 which has been utilised with such valuable results in the processes of fractional crystallisation4 ,the ,metals4--,the earlier attempts to reduce compounds of the rare earth elements to the metallic condition1 by means of metallic sodium or potassium1 did not yield pure products2 nor did the use of aluminium or magnesium lead to results of practical importance4 ,the metals were first obtained in a coherent physical condition by ,hillebrand and ,norton1#adg by electrolysis of the fused chlorides4 ,these investigators obtained cerium1 lanthanum1 and the so-called didymium1 and measured their specific heats2 their results confirmed the atomic weights assigned to the elements by ,mendelejeff1 except in the case of lanthanum4 ,their method has since been elaborated by ,muthmann1 ,hofer and ,weiss1#adh who have prepared large quantities of the cerium elements in the pure state4 ,more recently1 ,hirsch has prepared metallic cerium in large quantities1#adi and has studied its properties4 #adg ,pogg4 ,ann4 #ahge1 #aee1 #fca2 #aef1 #dff4 #adh ,annalen1 #aijb1 #cbj1 #bca2 see also ,muthmann and ,weiss1 ibid4 #aijd1 #cca1 #a4 #adi ,met4 ,chem4 ,eng4 #aiaa1 #i1 #edc4 ,by electrolytic reduction of the mixed chlorides of the cerium elements1 a mixture known as #8,misch metal' is obtained2 this has powerful reducing properties1 and1 like aluminium1 reduces the oxides of iron1 chromium1 etc41 with great development of heat4#aej ,the yttrium metals have not yet been obtained in the pure state1 the electrolytic method giving unsatisfactory results on account of the high melting-points of the metals1 and the volatile nature of their chlorides4 #aej ,a full account of the properties and preparation of the cerium metals and their alloys will be found in the monograph of ,kellermann1 #8,die ,ceritmetalle und ihre pyrophoren ,legierungen1 ,wilhelm ,knapp1 ,halle1 #aiab4 ,the cerium metals are white or slightly yellowish in colour1 and are moderately stable in dry air4 ,in moist air they tarnish slowly1 lanthanum1 as the most positive1 being most readily oxidised4 ,the melting-points and specific gravities are as follows3 ,element ,melting-point ,specific ,gravity ,cerium #fbc #gjbdb ,lanthanum #haj #faede ,praseodymium #idj #fdged ,neodymium #hdj #fiefc ,samarium #acjj-adjj #gg-gh ,the metals decompose water slowly in the cold1 but rapidly at the boiling-point1 with evolution of hydrogen4 ,they have a great affinity for oxygen1 the heats of formation of the oxides being of the order of those of alumina and magnesia3 ,heat of ,formation per ,equivalent ,weight of ,oxide#aea ,la,o #gda ,k ,nd,o #gbe ,pr,o #fhg ,ce,o #efa ,al,o #fdc ,mg,o #gai #aea ,muthmann and ,weiss1 loc4 cit42 ,k #a kilogram-calorie1 or #ajjj cal4 ,in consequence of the high values of the heats of combustion1 the metals have powerful reducing properties4 ,the cerium metals form alloys with magnesium1 zinc1 aluminium1 and iron1 and combine with boron and silicon4 ,the alloys of cerium1 and the metal itself1 are remarkable for their property of emitting brilliant sparks when scratched 7see ,chapter ,,xxi74 ,cerium also forms an amalgam with mercury4 ,the metals burn brilliantly when heated in oxygen1 and dissolve readily in dilute mineral acids4 ,when heated to a temperature of #bjj-cjj in a current of hydrogen1 they absorb the gas very readily1 forming the hydrides4 ,these compounds are also obtained by heating the oxides with magnesium in a current of hydrogen4 ,they were first prepared by ,winkler1#aeb who deduced from his analyses the general formula ,,rh2 the more recent work of ,muthmann and ,beck1#aec however1 points to the formula ,,rh4 #aeb ,ber4 #ahij1 #bc1 #bfdb2 #ahia1 #bd1 #hgc4 #aec ,annalen1 #aijd1 #cca1 #eh4 ,if nitrogen be substituted for hydrogen in either of the above methods of preparation1 nitrides of the general formula ,,rn are obtained2 cerium nitride1 however1 cannot be obtained by heating the element in the gas4#aed ,these compounds are also obtained when the carbides are heated in ammonia4 ,they are amorphous solids1 which yield ammonia when acted upon by water4 #aed ,dafert and ,miklanz1 ,monats4 #aiab1 #cc1 #iaa4 ,hydroxides4--,the hydroxides are thrown down as gelatinous precipitates on the addition of alkalies to hot dilute solutions of the salts2 precipitation in the cold1 or in strong solution1 usually gives a basic salt1 or an hydroxide mixed with a large quantity of basic salt4 ,the hydroxides are insoluble in excess of precipitant1 but the precipitation is inhibited by the presence of some organic hydroxy-acids4#aee #aee ,for effect of tartaric acid1 see p4 #acc4 ,the hydroxides are insoluble in water1 but dissolve very readily in acids4 ,the most basic of them absorb carbon dioxide from the air2 lanthanum hydroxide is exceptional in that it colours litmus blue4 ,whilst hydrogen peroxide in neutral solution does not react with rare earth salts1#aef alkalies in presence of this reagent precipitate gelatinous hydrated peroxides1 which are very unstable1 decomposing on standing1 or on treatment with acids1 with evolution of oxygen4 ,the general formula ,r,o x,h,o was proposed for these compounds by ,cleve1 but more recently the formula ,r7,,ooh77,,oh7 has been advanced4#aeg #aef ,compare behaviour of thorium and zirconium1 ,ch4 ,,xvi4 #aeg ,melikoff and ,pissarjewski1 ,zeitsch4 anorg4 ,chem4 #ahii1 #ba1 #gj2 ,melikoff and ,klimento1 ,chem4 ,zentr4 #aijb1 #a1 #agb4 ,oxides4--,in their most stable state of oxidation1 the rare earth elements are generally trivalent4 ,in the case of cerium1 the dioxide1 ,ce,o1 is more stable than the sesquioxide ,ce,o1 but the ceric salts are unstable1 and are very readily reduced to cerous compounds1 corresponding to the oxide ,ce,o4 ,higher oxides are known with certainty among the other elements only in the cases of praseodymium and terbium1 but these do not give rise to salts4 ,the oxides ,r,o are fairly strong bases1 being comparable in strength to the alkaline earths1 and far more strongly basic than alumina and oxides of other trivalent elements2 thus they liberate ammonia from ammonium compounds1 whilst the salts they form with strong acids are not easily hydrolysed4 ,their relative strengths as bases are expressed in the following series1 in which the elements are placed in order of diminishing electropositive character3#aeh ,la1 ,ce1 ,pr1 ,nd1 ,yt1 ,eu1 ,gd1 ,sa1 ,tb1 ,dy1 ,ho1 ,er1 ,tm1 ,yb1 ,lu1 ,sc1 ,ceiv4 #aeh ,the position of yttrium in this series is not known with certainty2 it is probably as positive as neodymium4 ,it is usually stated 7see ,meyer and ,hauser1 pp4 #cb-cc7 that the terbia oxides are intermediate in basic strength between the ceria and yttria earths1 though the arrangement into two series1 consisting of the cerium and yttrium groups respectively1 is generally adopted2 the electropositive character of the elements in each series then weakens as the atomic weight rises1 scandium being of course exceptional4 ,it will be seen that1 with the exception of scandium and yttrium1 the metals of the cerium and yttrium groups become less electropositive as the atomic weight increases4 ,this arrangement is obtained by ascertaining the order in which the various hydroxides are precipitated from a solution by gradual addition of a dilute solution of a strong base4 ,the weakest base is precipitated first1 and the strongest last2 those intermediate in strength are thrown down in ascending order of strength4 ,similar results may be obtained by the fractional decomposition of the nitrates by heat2 in this case the nitrate of the weakest base is decomposed at the lowest temperature4 ,this order is also confirmed1 as far as the data are available1 by measurements of the equivalent conductivities of solutions of the salts 7see1 for example1 p4 #abb74 ,quite recently1 a very different order has been obtained from a consideration of the dissociation tensions1 and of the heats of dissociation of the anhydrous sulphates4#aei ,in the following table the elements are arranged in the order of the increase of the dissociation tension 7,t7 measured at #ijj1 which is the same as the order of decrease of the heats of dissociation 7,q73 ,element ,at4 ,wt4 ,t4 7,mm4 ,hg47 ,q4 ,la #acij #b #eih ,yt #hij #c #ehi ,lu #agdj #ce #ehe ,yb #agbj #d #ehb ,er #afgg #e #egf ,pr #adjf #ee #egd ,nd #addc #f #egb ,gd #aegc #g #efi ,sa #aejd #h #efe ,sc #dda #aa #ede ,ce #adjbe #ebd #aei ,whler and ,grnzweig1 ,ber4 #aiac1 #df1 #agbf4 ,it will be observed that the order is very different from the order of increase of atomic weight1 the positions of lutecium and ytterbium being especially surprising2 these elements are generally considered to be among the least electropositive of the whole series4 ,the anomalous position of cerium is probably due to the fact that the sulphate on decomposition leaves the dioxide1 and not the sesquioxide1 as with the other elements2 this would undoubtedly affect the values4 ,the heats of dissociation are the greatest yet observed for the sulphates of trivalent metals1 a further evidence of the strongly basic nature of the oxides4 ,ignited lanthana resembles quicklime in that it readily absorbs carbon dioxide from the air1 and hisses when slaked with water2 as the basicity becomes weaker1 the affinity for water and carbon dioxide becomes less marked4 ,all the oxides are soluble in dilute acids1 even after prolonged ignition2 but the ease with which solution occurs is naturally much influenced by the treatment to which the oxide has been subjected1 as well as by its strength as a base4 ,the rare earth oxides are capable of existing in more than one modification1 the compounds obtained by ignition of the hydroxides differing in appearance and reactivity from those prepared by ignition of the oxalates or nitrates1 and so on2 they are probably highly polymerised4 ,cerium dioxide1 ,ce,o1 is remarkable for its power of combining with the other oxides1 ,r,o1 of the rare earth metals4 ,the pure dioxide is insoluble in nitric acid1 but mixtures of earths containing up to #ej per cent4 of the dioxide dissolve readily4 ,the various colours of mixtures of the ceria earths may sometimes be attributed to a similar combination1#afj and there can be little doubt that the dioxide sometimes functions as an acid in the rare earth minerals4 #afj ,the brown colour of a mixture of ceria oxides containing praseodymium is generally attributed to the presence of the strongly coloured peroxide of that element4 ,sulphides4--,these compounds cannot be prepared in the wet way1 that is1 by the action of hydrogen sulphide or ammonium sulphide on the salts in solution2 the former reagent gives no precipitate1 the latter throws down the hydroxides4 ,in this behaviour1 the rare earth elements resemble aluminium and chromium4 ,the normal sulphides1 ,r,s1 are obtained by reduction of the anhydrous sulphates1 or from the oxides at high temperatures1 by treatment with hydrogen sulphide4 ,they are strongly coloured compounds1 fairly stable towards cold water1 but readily hydrolysed on boiling4 ,disulphides1 ,,rs1 are known in the cases of cerium1 lanthanum1 and praseodymium2 these are to be regarded as polysulphides1 since on treatment with dilute acids they yield hydrogen persulphide1 ,h,s4 ,carbides4--,by reduction of the oxides with carbon in the electric furnace1 ,moissan obtained the carbides in the form of microscopic yellow crystals4 ,they have the general formula ,,rc1 and are attacked by water and dilute acids1 with evolution of very complex mixtures of gases4#afa ,the principal product is acetylene1 with various higher homologues1 and in smaller quantities ethylene and ethane and their homologues4 ,no methane is formed1#afb but hydrogen is always present1 the olefines and paraffins probably arising from its action on the acetylenic hydrocarbons4 ,the relation of the rare earth elements to the calcium group is here very close2 calcium carbide when attacked by water yields pure acetylene1 whereas aluminium carbide gives pure methane4 #afa ,damiens1 ,compt4 rend4 #aiac1 #aeg1 #bad4 #afb ,moissan stated that #bd-cj per cent4 of methane was formed in this action2 compare ,compt4 rend4 #aijj1 #aca1 #eie4 ,halogen ,salts4--,the halides of the rare earth elements show a close analogy with the corresponding compounds of the alkaline earth elements4 ,the fluorides are insoluble in water and dilute mineral acids1 and are obtained as gelatinous precipitates by the addition of hydrofluoric acid1 or a soluble fluoride1 to solutions of the salts4 ,they may be prepared in the crystalline condition by heating the carbides in a stream of fluorine1 or by the action of hydrofluoric acid upon the hydroxides in aqueous suspension4 ,the rare earth elements1 as well as thorium1 may be separated from zirconium by taking advantage of the insolubility of their fluorides in excess of hydrofluoric acid or alkali fluorides1 since zirconium fluoride is readily soluble in excess of the precipitant4 ,the solubility of the fluorides in a large excess of concentrated acid increases with the electropositive character of the metal1 the fluorides of the more negative elements being the least soluble4 ,thorium and scandium may1 therefore1 be concentrated to a large extent by repeated precipitation with hydrofluoric acid in acid solution4 ,the silicofluorides of the rare earth elements have been used by ,r4 ,j4 ,meyer in the extraction of scandium from wolframite 7see ,chapter ,i and under ,scandium1 p4 #bae74 ,they are thrown down as gelatinous precipitates on addition of potassium or sodium silicofluoride to boiling1 neutral solutions of rare earth salts4 ,in presence of mineral acids1 however1 they are not thrown down in the cold2 on boiling1 the cerium metals are precipitated as fluorides1 by hydrolysis of the silicofluorides--the yttrium elements1 with the exception of scandium1 being held in solution by the mineral acid4 ,with the exception of the fluorides1 the halogen salts of the rare earth metals are readily soluble in water1 and crystallise from the concentrated solutions in the hydrated form4 ,the bromides and iodides have not been so fully studied as the chlorides2 they are hygroscopic salts1 and decompose rather easily4 ,the iodides have been obtained by ,moissan in the anhydrous state1 by the action of iodine vapour on the carbides at high temperature4 ,the anhydrous chlorides may be obtained by the application of any of the ordinary methods1 e4g4 by heating the oxides with carbon in a stream of chlorine1 by heating the carbides in the same gas1 by heating the sulphides or hydrated chlorides in hydrogen chloride1 or by evaporating the solutions of the hydrated salts to dryness in presence of ammonium chloride1 and then igniting till the latter has all been removed4 ,as obtained by any of these methods1 they are fusible at a red heat1 but only slightly volatile2 they are easily soluble in water or alcohol1 with disengagement of heat4 ,they are insoluble in most organic solvents1 but dissolve to some extent in some bases2 the chlorides of the yttrium elements1 for example1 are readily soluble in pyridine4 ,with such solvents1 the chlorides form compounds which may be considered as derived from the hydrated forms1 by replacement of the so-called water of crystallisation by the organic base4 ,conductivity measurements show that the salts are not perceptibly hydrolysed in moderately dilute aqueous solutions1 though the values for the equivalent conductivities vary somewhat with the variations in the electropositive character of the elements4 ,in the following table1 the equivalent conductivities of the chlorides in solutions of dilution #cb and #ajbd at #be;,c4 are given4 ,it will be seen that the value 7 - 7 #aj is in all cases 7except for the highly hydrolysed scandium salt7 very close to #c1 an experimental proof of the trivalent nature of the elements4 ,the values for the chlorides of iron1 aluminium and chromium are included2 it will be seen that these elements are considerably less positive than the rare earth metals 7with the exception1 of course1 of scandium74 ,salt - ,la,cl #ajeh #acae #beg ,ce,cl #ajgh #aceb #bgf ,pr,cl #ajee #acei #cjd ,nd,cl #ajch #acdc #cje ,yt,cl #ihh #abcd #bdf ,yb,cl #ajgd #adjd #ccj ,sc,cl #aafi #begi #adaj ,al,cl #iii #achj #cha ,cr,cl #ihd #aebf #edb ,fe,cl #aagb #bjjg #hce ,from aqueous solutions the chlorides crystallise with six molecules of water1 except praseodymium chloride1 which has seven4 ,the hydrated salts1 when heated to #abj in the air1 form insoluble oxychlorides of the general formula ,r,o,cl4 ,the chlorides do not show a great tendency to form double salts with other metallic chlorides2 on the other hand1 they readily form complex compounds with the chlorides of the less electropositive metals1 e4g4 tin1 bismuth1 gold1 and platinum4 ,subchlorides of samarium and europium have recently been obtained2 in these compounds1 for the first time1 rare earth metals have been shown to be capable of functioning as divalent elements4 ,cyanides of the rare earth elements are not known2 addition of potassium cyanide to solutions of the salts throws down the hydroxides4 ,the platinocyanides may be obtained by double decomposition of the sulphates with barium platinocyanide4 ,they are very stable and characteristic bodies1 of the general formula ,r,pt7,,cn71 with #ah or #ba molecules of water4 ,the compounds of the cerium elements are yellow1 with a strong blue fluorescence2 they crystallise in the monoclinic system4 ,the platinocyanides of the yttrium metals are red or crimson1 with a splendid green fluorescence1 and crystallise in the rhombic system4 ,scandium platinocyanide is of great interest from the fact that it exists in two modifications1 which show the characteristic appearance of the two groups of compounds respectively4 ,potassium ferrocyanide precipitates potassium earth ferrocyanides of the general formula ,,kr7,fe,c,n71#c;,h,o1 from neutral solutions2#afc the precipitate is somewhat soluble in excess4 ,the ferrocyanides have been proposed for the purification of yttrium2 the method is useful where rapid concentration of the element is required1 yttrium ferrocyanide being far more soluble than the analogous compounds of the erbium and ytterbium metals1 but the precipitates are gelatinous1 and very difficult to handle4 #afc ,compare ,astrid ,cleve1 ,zeitsch4 anorg4 ,chem4 #aijb1 #cb1 #abi4 ,halogen ,oxy-salts4--,perchlorates and periodates of the rare earth elements1 of the general formula ,r7,,xo71x,h,o1 have been obtained4 ,the existence of chlorates has been observed only in the yttrium group2 yttrium chlorate1 ,yt7,cl,o71#h;,h,o1 has been prepared by double decomposition of the sulphate with barium chlorate4 ,the bromates are also prepared in this way4 ,they are readily soluble compounds1 of which several hydrated forms are known4 ,they are of considerable importance for purposes of separation in the yttrium group4 ,the iodates are sparingly soluble bodies1 precipitated by addition of the alkali compound to solutions of the rare earth salts4 ,the rare earth iodates are soluble in nitric acid1 the solubility increasing as the electropositive character of the element becomes stronger4 ,a method for the purification of yttrium has recently been based upon this property of the iodates1 whilst the fact that thorium iodate is completely insoluble in nitric acid allows of the easy separation and estimation of thorium in minerals or mixtures containing rare earth elements4 ,sulphates4--,the sulphates of the rare earth elements are obtained by dissolving the oxides or hydroxides in sulphuric acid4 ,from the solutions so obtained1 various hydrated salts separate according to the temperature of crystallisation4 ,by heating the hydrated salts to a temperature of #cjj-djj1 the anhydrous salts are prepared4 ,these are extremely soluble in water at #j1 having a great tendency1 which is indeed to be observed in the hydrated forms also1 to form supersaturated solutions4 ,when the temperature of such a solution is allowed to rise1 larger or smaller quantities of an hydrated form separate out1 the differences of solubility among the sulphate hydrates of the various elements being sometimes considerable4 ,the hydrated sulphates of the cerium elements have been very closely studied in connection with the purification of thorium4 ,cerium sulphate itself forms hydrates with #ab1 #i1 #h1 #e1 and #d molecules of water1 but sulphates of the other elements generally form fewer hydrates2 the commonest have #ab1 #h1 or #d molecules of water1 and numerous cases of isomorphism are known among them4 ,the solubility curve of the cerium sulphate hydrates is shown in the diagram4 ,fig4 #c4 ,the sulphates of the yttrium elements have not yet been systematically investigated1 and in most cases only the octohydrates are known4 ,scandium sulphate is notably different from the other sulphates1 in that it is considerably more soluble1 and crystallises with six molecules of water4 ,illustration3 ,,fig4 #c4 ,it is an important characteristic of the rare earth elements that the solubility of the sulphates diminishes rapidly as the temperature rises4 ,the study of the various equilibrium conditions is greatly complicated by the tendency to form supersaturated solutions1 and the fact that many hydrates can exist throughout considerable ranges of temperature in the metastable condition2 in consequence of this1 also1 the solubilities of many hydrates are known for temperatures far beyond the transition points4 ,foreign elements may be separated by taking advantage of the very great solubility of the anhydrous sulphates at #j1 and the rapid decrease in solubility with rise of temperature4 ,for this purpose1 a solution of the anhydrous sulphates saturated at #j is prepared1 and after filtration is slowly allowed to come to room temperature2 the hydrated rare earth sulphates then separate1 leaving in solution the foreign sulphates4 ,this method may indeed be used instead of the oxalate separation 7see p4 #adg74 ,in presence of excess of sulphuric acid1 acid sulphates of the general formula ,r7,,hso7 are formed4 ,these are fairly stable1 and must be heated to a temperature of #djj-ejj to decompose them completely to the normal salts2 even at that temperature1 traces of acid are tenaciously retained1 a fact which renders the determination of the equivalents by the sulphate method unreliable1 unless special precautions are taken4 ,on further heating1 the normal sulphates pass into basic salts1 ,r,o1,,so1 and finally1 at the temperature of the blowpipe flame1 into the oxides4 ,the temperatures at which these decompositions occur vary with the positive character of the elements2 the most basic oxide clings most tenaciously to sulphuric anhydride1 and forms the most stable acid salt4 ,lanthanum sulphate1 for example1 requires to be heated for a considerable time at a white heat if the pure oxide is required1 whilst the sulphates of the less positive elements are easily decomposed at a red heat4 ,the order of basic strength of the oxides1 as determined by the ease with which the sulphates are decomposed1 seems1 however1 to be very different from the order determined by decomposition of the nitrates 7see p4 #aah74 ,with the alkali sulphates1 the sulphates of the rare earth elements readily form double salts1 which are of great importance in separation1 on account of the great differences in solubility4 ,the double sulphates of the cerium group are almost insoluble in excess of alkali sulphate1 whereas the yttrium double sulphates1 with the exception of those of the terbium metals1 which occupy an intermediate position1 are very easily soluble4 ,this method of separating the elements into the two main groups was first employed by ,berzelius1 and though a century has elapsed1 it remains to-day the most efficient method of effecting the separation4 ,the ethylsulphates have been employed by ,urbain and others in effecting separations1 especially in the erbium and terbium groups4 ,the solubilities of these salts are in the same general order as those of the alkali double sulphates1 and they are especially convenient for separating the metals into the three groups of the cerium1 terbium1 and yttrium elements respectively4 ,they may be prepared by double decomposition of the rare earth sulphates with barium ethylsulphate1 but on account of the ease with which the alkylsulphates are hydrolysed by acids1 it is essential that the solutions should be quite neutral4 ,a more convenient method1 according to ,james1 is the treatment of the anhydrous chlorides in alcohol solution with sodium ethylsulphate dissolved in the same medium2 sodium chloride is precipitated1 whilst the ethylsulphates of the rare earth elements remain in solution4 ,the sulphites of the rare earth elements are sparingly soluble crystalline salts1 of the general formula ,r7,,so71x,h,o4 ,they are obtained by passing sulphur dioxide into a suspension of the hydroxides in water1 or by double decomposition of soluble salts with alkali sulphite4 ,they dissolve in excess of sulphurous acid1 and on evaporation of the solution are deposited unchanged4 ,they are distinguished from thorium sulphite by the fact that they form no alkali double salts4 ,the strongly electropositive character of the rare earth metals is shown by the fact that they form normal and not basic sulphites4 ,the thiosulphates are readily soluble1 crystalline bodies4 ,with the exception of the ceric and scandium salts1 they are not hydrolysed in boiling solution1 a fact which allows of a complete separation from the readily hydrolysed thiosulphates of zirconium and thorium4 ,dithionates of the commoner rare earth elements1 of the general formula ,r7,s,o71x,h,o1 have been prepared by double decomposition of the sulphates with barium dithionate4 ,they are readily soluble1 crystalline salts4 ,the selenates are soluble1 crystalline salts1 which separate from aqueous solutions in various hydrated forms4 ,they resemble the sulphates in being less soluble in hot than in cold water1 and numerous cases of isomorphism have been observed among the corresponding sulphate and selenate hydrates4 ,several alkali double selenates have been described2 they show a close resemblance to the analogous double sulphates4 ,the selenites are amorphous1 insoluble compounds1 obtained by the action of selenious acid on the carbonates1 or on solutions of neutral salts4 ,basic and acid selenites are also known4 ,nitrates4--,the nitrates are crystalline1 deliquescent compounds1 readily soluble in water and alcohol1 but less easily in nitric acid1 a fact which has been of considerable importance for purposes of separation4 ,the solubility is greatest in the case of lanthanum nitrate1 diminishing through the cerium group to a minimum in gadolinium nitrate1 and then increasing again4 ,they separate from aqueous solution in the form of crystalline hydrates2 in the cerium group1 these have commonly the formula ,r7,,no71#f;,h,o1 whilst the nitrates of the yttrium elements usually crystallise with #c or #e molecules of water4 ,by carefully heating the hydrated salts1 basic nitrates may be obtained1 which in the yttrium group are soluble in water1 and may be obtained crystalline2 in the cerium group1 the basic nitrates are insoluble4 ,by further heating1 insoluble #8superbasic salts1' and finally the oxides1 are obtained in all cases4 ,the temperatures at which these basic and superbasic compounds are formed vary with the electropositive character of the element2 this fact affords a method of separation which has been very frequently employed4 ,an interesting series of addition compounds of the rare earth nitrates with antipyrine 7dimethylphenylpyrazolone1 ,c,h,,on7 has been described recently by ,kolbe4#afd ,those of the cerium metals have the general formula ,r7,,no71#c;,c,h,,on2 the yttrium nitrates appear to combine with four molecules of the base4 #afd ,zeitsch4 anorg4 ,chem4 #aiac1 #hc1 #adc ,the tendency to form double nitrates with nitrates of the metals of ,group ,,ia and ,group ,,iia also varies with the basic strength of the hydroxides4 ,in the most positive elements of the cerium group1 the tendency is very pronounced1 and there are a large number of stable1 crystalline double salts2 but the stability decreases rapidly as the atomic weight of the element rises1 and in the terbium and yttrium groups crystallised double nitrates cannot be obtained4 ,the solubility of these double salts increases rapidly in the same direction1 the lanthanum double nitrates being the least soluble4 ,for this reason1 these compounds are of great importance for the purpose of separation1 especially in the cerium group4 ,bismuth nitrate and the various bismuth double nitrates are isomorphous with the corresponding compounds of the cerium group1 and the double bismuth ammonium and bismuth magnesium salts have been largely used by ,urbain in the separation of samarium and the elements of the terbium group4 ,phosphates4--,addition of phosphoric acid1 or an alkali phosphate to solutions of rare earth salts throws down the phosphates as gelatinous precipitates1 which slowly become crystalline on standing4 ,the precipitate is soluble in excess of phosphoric acid1 and in other mineral acids1 a fact of great importance in the commercial treatment of monazite4 ,the composition of the precipitate is not known with certainty2 both neutral and acid phosphates can probably be obtained according to the conditions4 ,double salts with the alkali phosphates can be prepared by fusion methods4 ,the naturally occurring phosphates1 monazite and xenotime1 are mixtures of the orthophosphates of the cerium and yttrium elements respectively4 ,phosphites are known in a few cases only2 arsenates and arsenites of lanthanum have been prepared4 ,vanadates of some of the rare earth elements have been described4 ,chromates4--,the rare earth chromates are1 as a rule1 sparingly soluble in water1 and show considerable differences of solubility amongst themselves2 for this reason1 they have been of some use in the separation of the cerium elements4#afe ,they are obtained by addition of potassium chromate to neutral solutions of rare earth salts as crystalline precipitates1 of the general formula ,r7,cr,o71#h;,h,o2 with a large excess of alkali chromate1 double chromates are obtained1 which are more readily formed1 and more soluble1 in the yttrium series than in the cerium group4 ,addition of chromic acid or alkali bichromate to solutions of the soluble salts gives no precipitate1 a fact which allows of the separation of zirconium and thorium1 and of cerium in the tetravalent state1 since the tetravalent elements are precipitated by both these reagents4 #afe ,muthmann and ,bhm1 ,ber4 #aijj1 #cc1 #db2 ,bhm1 ,zeitsch4 angew4 ,chem4 #aijd1 #ae1 #cgb and #abhb4 ,ammonium molybdate throws down from neutral solution of rare earth salts gelatinous precipitates of the molybdates2 the formula ,la#b7;,h,mo,o7 is assigned to the lanthanum compound obtained in this way4 ,no precipitation occurs if the solution be strongly acid2 on this fact a process has recently been based for the volumetric estimation of thorium1 in presence of rare earth salts1 by means of ammonium molybdate 7see p4 #bhi74 ,various silicotungstates and double tungstates have been described4 ,carbonates4--,the more pronounced electropositive character of the rare earth elements1 as contrasted with other trivalent metals1 is well illustrated by the fact that they form stable neutral carbonates of the formula ,r7,,co71x,h,o4 ,these may be obtained by passing a current of carbon dioxide through an aqueous suspension of the hydroxides1 or by addition of an alkali carbonate to neutral solutions of the salts4 ,basic carbonates are known in the case of the less positive yttrium elements only2 both these and the neutral carbonates are insoluble in water4 ,in presence of a large excess of alkali carbonate1 double carbonates are formed4 ,the stability as well as the solubility of these compounds increases in passing from the cerium to the yttrium group1 i4e4 as the electropositive character becomes weaker4 ,the double carbonates of the cerium elements are sparingly soluble1 and are decomposed by water1 especially on warming2 they may1 however1 be recrystallised from alkali carbonate solution4 ,the sodium and ammonium double salts are less soluble than the potassium compounds4 ,the latter have the general formula ,r7,,co71,k,,co1#ab;,h,o1 and are of considerable importance in many processes of separation4 ,the yttrium elements can be separated from the cerium metals1 and the latter from one another1 by taking advantage of the differences of solubility shown by the potassium double carbonates4 ,if a concentrated solution of the salts in potassium carbonate solution be fractionally diluted with water1 the cerium elements separate in the order3 lanthanum1 praseodymium1 cerium1 neodymium1 and samarium2 the more soluble yttrium compounds remain in the solution4 ,thorium forms double alkali carbonates which are very readily soluble in excess of alkali carbonate2 this property is of great importance for the technical separation of the element4 ,oxalates4--,the oxalates of the rare earth elements are of the greatest importance1 on account of the fact that they are not only insoluble in water1 but are also very sparingly soluble in dilute mineral acids1 and in excess of oxalic acid4 ,they can be completely precipitated even from strongly acid solutions by addition of sufficient excess of oxalic acid1 or alkali oxalate1 and thus afford a means of easily and completely separating the rare earth group from the commoner elements4 ,they are thrown down by addition of oxalic acid1 or alkali oxalate1 as amorphous precipitates1 which rapidly become crystalline1 especially if the solution is warmed4 ,from water at normal temperatures they usually separate as the decahydrates1 ,r7,c,o71#aj;,h,o1 but hydrates with #g1 #i1 and #aa molecules of water of crystallisation are also known4 ,from strongly acid solutions1 mixed oxalo-salts of the general formula ,r7,c,o7,x1 where ,x ,cl1 ,,no1 ,,hso1 etc41 may be obtained4 ,these mixed salts may also be prepared by dissolving the oxalates in concentrated solutions of the chlorides1 nitrates1 etc41 whilst nitro-sulphates1 ,r7,,so7,,no1 have been obtained by recrystallising the sulphates from strong nitric acid4 ,the tendency to form salts with mixed acid radicles appears to be general4#aff #aff ,see ,meyer and ,marckwald1 ,ber4 #aijj1 #cc1 #ajjc2 also ,matignon1 ,ann4 ,chim4 ,phys4 #aijf1 viii41 #h1 #bdc4 ,the solubilities of the oxalates in mineral acids of various concentrations have been examined by ,hauser and ,wirth4#afg ,whilst the solubilities in water are exceedingly slight1 and increase with increasing atomic weight of the elements1 i4e4 from the cerium to the yttrium group1 in mineral acids of concentration #c-d,n the solubility becomes noticeable1 and is greatest for the oxalates of the most positive elements4 ,the solubility is greatly lessened1 however1 if considerable excess of oxalic acid be present4 #afg ,zeitsch4 anal4 ,chem4 #aijh1 #dg1 #chi4 ,double oxalates with the alkali oxalates can be obtained with the salts of the yttrium elements only1 the oxalates of the cerium elements being almost insoluble in excess of alkali oxalate in the cold4 ,of the alkali double oxalates1 the potassium compounds are the most soluble1 but the ammonium compounds show the greatest differences in solubility2 von ,welsbach has employed the method of fractional crystallisation of these salts from a saturated solution of ammonium oxalate for separations in the yttrium group4 ,the sodium double oxalates are the least soluble of these double salts4 ,since the rare earth elements are almost always separated in the form of the oxalates1 the methods for transforming these into soluble compounds become important4 ,they may be ignited to oxides1 and these dissolved in nitric acid2 if the content of ceria is very high1 the oxide mixture may become insoluble1 but this difficulty may be overcome by addition of a reducing agent--hydrogen peroxide is very convenient for this purpose4 ,the oxalates may also be dissolved directly in fuming nitric acid1 care being taken to avoid loss2 if the mixture contains cerium1 the oxidation is hastened1 ceric salts having the property of acting as oxygen carriers4 ,by boiling for a short time with potash1 the oxalates may be easily transformed into the hydroxides1 which can be dissolved in dilute acids4 ,formates4--,on account of the considerable differences in solubility by which they are characterised1 these salts have been employed for separations4 ,the formates of the cerium group are considerably less soluble than those of the yttrium group4 ,they may be partly precipitated from solutions of rare earth salts by addition of alkali formate--formic acid itself causes precipitation only with salts of weak acids1 e4g4 the acetates--but are best prepared by dissolving the oxides in formic acid2 on concentration of the solution1 the formates of the cerium and terbium elements successively separate1 the salts of the yttrium group remaining in solution4 ,the separation of the terbium earths by this method was attempted by ,delafontaine2 his #8new' element1 ,philippium1 obtained from the mother-liquors1 was in reality a mixture of the terbium and yttrium elements1 which cannot be completely separated by the formate method4#afh #afh ,see ,urbain1 ,ann4 ,chim4 ,phys4 #aijj1 vii41 #ai1 #ahd4 ,the acetates are readily soluble in water1 the yttrium salts being rather less easily soluble than those of the cerium group4 ,they are therefore obtained by dissolving the oxides in acetic acid2 addition of alkali acetate to a solution of a rare earth salt gives no precipitate1 even on boiling1 behaviour which is in marked contrast to the ease with which the salts of other trivalent metals are hydrolysed under these conditions4 ,in this respect the rare earth elements differ also from the tetravalent elements zirconium and thorium 7and from cerium in the tetravalent state72 soluble salts of the latter1 on boiling with sodium acetate1 give insoluble basic acetates4 ,even sparingly soluble compounds of the rare earth elements are as a rule taken into solution by digestion with ammonium acetate4 ,tartrates4--,addition of ammonium tartrate to a neutral solution of rare earth salts throws down an amorphous precipitate1 which dissolves easily in acids1 and in excess of the precipitant4 ,in the presence of tartaric acid1 precipitation of the earths by addition of sodium hydroxide is completely inhibited4 ,potassium hydroxide under these conditions gives a precipitate in the case of the yttrium elements1 though only on boiling2 ammonia gives a crystalline precipitate even in the cold with this group4 ,these precipitates are alkali double tartrates of the yttrium metals2 the cerium elements give no precipitate at all4 ,in all cases1 therefore1 the precipitation of the hydroxides is inhibited by the presence of tartaric acid4 ,a very large number of organic salts of the rare earth elements has been prepared and examined during the past two decades1 in the endeavour to find some class of compounds which will allow of an easy separation of the group4 ,the benzoates1 succinates1 hippurates1 citrates and similar relatively simple salts first received attention1 but less common acids1 as e4g4 the hydroxynaphthalenesulphonic acids1 have also been employed4#afi ,the use of various organic acids for the separation and estimation of thorium in presence of the rare earths is outlined in that connection 7see p4 #bhh74 ,more recently1 the glycollates and cacodylates have been prepared4 ,the glycollates#agj of the cerium elements have the general formula ,r7,c,h,o71 and crystallise in crusts2 they are more soluble than the yttrium compounds1 which have the formula ,r7,c,h,o71#b;,h,o1 and crystallise in needles4 ,the cacodylates1#aga ,r,as7,,ch7,o1 crystallise with #af or #ah molecules of water1 and have similar solubility relations4 #afi ,erdmann and ,wirth1 ,annalen1 #aijh1 #cfa1 #aij2 see also ,pratt and ,james1 ,j4 ,amer4 ,chem4 ,soc4 #aiaa1 #cc1 #accj2 ,baskerville and ,turrentine1 ibid41 #aijd1 #bf1 #df2 ,james1 ,hoben and ,robinson1 ibid41 #aiab1 #cd1 #bgf1 etc4 #agj ,jantsch and ,grnkraut1 ,zeitsch4 anorg4 ,chem4 #aiac1 #gi1 #cje4 #aga ,whittlemore and ,james1 ,j4 ,amer4 ,chem4 ,soc4 #aiac1 #ce1 #fbg4 ,the phthalates of the yttrium group have been found to be very valuable for purposes of separation by ,meyer and ,wuorinen4#agb ,the salts are readily obtained in solution by shaking together cold aqueous suspensions of the rare earth hydroxides1 and phthalic acid2 the clear solutions when warmed become cloudy1 the organic salts hydrolysing very easily1 with separation of the hydroxides4 ,the most positive elements naturally remain longest in the solution1 the weakly basic oxides accumulating in the first precipitates4 #agb ,zeitsch4 anorg4 ,chem4 #aiac1 #hj1 #g4 ,an organic compound which has proved very useful in the treatment of the rare earths is acetylacetone1 ,,ch4,,co4,,ch4,,co4,,ch4#agc ,in its enolic form1 this substance forms salts with metals1 which in the case of the rare earth elements are especially characterised by the ease with which they may be obtained1 and their high crystallising power4 ,they may be prepared by double decomposition of neutral solutions of rare earth salts with ammonium acetylacetone1 and crystallise readily from dilute alcohol4 ,they have been used by ,urbain in the fractionation of the yttrium group1 and for determination of molecular weights by the boiling point method2 ,biltz#agd has shown that in solution they generally have the double formula ,r7,c,h,o74 #agc ,urbain1 ,bull4 ,soc4 chim4 #ahig1 iii41 #ag1 #ih2 ,urbain and ,budischofsky1 ,compt4 rend4 #ahig1 #abd1 #fah2 ,biltz and ,clinch1 ,zeitsch4 anorg4 ,chem4 #aijd1 #dj1 #bah4 #agd ,annalen1 #aijd1 #cca1 #ccd4 ,,the ,,rare ,,earth ,,elements1 ,,and ,,the ,,periodic ,,classification ,at the time of the introduction of the periodic classification the rare earth elements were generally believed to be divalent4 ,this belief1 which has persisted until quite recently1#age was based chiefly on the electropositive character of the metals1 and their general chemical resemblance to the elements of the alkaline earths2 the isomorphism of the tungstates of calcium and the cerium elements1 and of the molybdates of lead and the cerium elements1 also supports this view4 ,the physical evidence in favour of ,mendelejeff's view1 however1 is quite overwhelming2 the specific heats of the metals1 the equivalent conductivities of the chlorides1 and molecular weight determinations by means of vapour densities and the boiling point method1 prove beyond doubt that the elements are in fact trivalent4 #age ,see ,wyrouboff1 ,bull4 ,soc4 franc4 ,min4 #ahif1 #ai1 #bai2 ,wyrouboff and ,verneuil1 ,compt4 rend4 #ahig1 #abd1 #abcj and #acjj2 ibid41 #ahii1 #abh1 #aegc2 etc4 ,in deciding in favour of the trivalent nature of the rare earth metals1 ,mendelejeff was influenced chiefly by the fact that there was no room in the table for divalent elements with the equivalent weights then assigned to the cerium and yttrium elements4 ,at that time1 only the six oxides obtained by ,mosander were known2 of these the accepted equivalents and atomic weights were as follows3 ,element4 ,equivalent4 ,atomic ,weight4 ,lanthanum #df #ib ,cerium #df #ib ,didymium #dh #if ,yttrium #ca #fb ,erbium #ef #aab the values for terbium being uncertain4 ,if cerium be considered trivalent in the cerous salts1 its atomic weight becomes #ach1 that of barium being #acf4 ,mendelejeff placed cerium in ,group ,,iv1 series #h1 in the position which it still occupies2 he pointed out that the accepted equivalent must be too low1 and suggested that the atomic weight should be at least #adj1 almost exactly the value accepted to-day4 ,this choice left the positions in ,group ,,iii1 series #h1 horizontally before cerium1 and in ,group ,,iv1 series #aj1 vertically below it 7see figure71 to be filled by the two elements1 lanthanum and didymium4 ,no chemical evidence being available to decide the choice1 he provisionally assigned didymium to the first 7,group ,,iii1 series #h71 and lanthanum to the second 7,group ,,iv1 series #aj7 position1 at the same time expressing the opinion that didymium was probably a mixture of closely related elements4 ,yttrium then fell into place in ,group ,,iii1 series #f1 above didymium1 and erbium in ,group ,,iii1 series #aj1 below it4 ,to the vacant space above yttrium in ,group ,,iii1 series #d1 he assigned the hypothetical element ,eka-boron1 with atomic weight #dd2 this space is now occupied by scandium1 which corresponds almost exactly in properties to the metal described by the ,russian chemist4 ,a part of the table illustrating these positions is shown in ,fig4 #d4 ,the determination of the specific heats of the metals by ,hillebrand and ,norton in #ahge1 whilst confirming the trivalency of the elements1 rendered it necessary to alter the position of lanthanum1 which was placed in ,group ,,iii1 series #h1 instead of didymium1 which was thus left without a place4 ,this first indication that all the rare earth elements could not be fitted into the table without difficulties was soon followed by the discovery of several other members of the group1 for which places could not easily be found4 ,illustration3 ---------------------------------------- ----------------- ,group #j ,i ,,ii ,,iii ,,iv ,v ,a ,b,a ,b,a ,b,a ,b,a ---------------------------------------- ----------------- ,series #a ,h ---------------------------------------- ----------------- #b ,li ,be ,b ,c ---------------------------------------- ----------------- #c ,na ,mg ,al ,si ---------------------------------------- ----------------- #d ,k ,ca ,eka- ,ti boron #e ,cu ,zn ---------------------------------------- ----------------- #f ,sr ,yt ,zr #g ,ag ,cd ,sn ---------------------------------------- ----------------- #h ,ba ,di8 ,ce #i ---------------------------------------- ----------------- #aj ,er ,la8 #aa ,au ,hg ,pb ---------------------------------------- ----------------- #ab ,th ---------------------------------------- ----------------- ,,fig4 #d4--,,part ,,of ,,the ,,periodic ,,table1 ,,showing ,,the ,,positions ,,originally ,,assigned ,,to ,,the ,,rare ,,earth ,,elements ,,by ,,mendelejeff ,it was first pointed out by ,brauner in #ahha that1 with the exception of scandium 7#dda7 and yttrium 7#hij71 the rare earth elements form a zone of increasing atomic weight between barium 7#acgcg7 and tantalum 7#ahae74 ,in #aijb he proposed#agf to consider the rare earth metals as a kind of zone or belt among the elements1 comparable to the asteroids in the solar system1 extending from cerium in ,group ,,iv to tantalum in ,group ,v in a continuous series4 ,the suggestion seems at first sight contrary to the whole principle of periodic classification1 but it accords very well with the anomalous position of the rare earth group among the other elements2 it is very well illustrated in the accompanying ,fig4 #e1 which shows an helical or space representation of the table4 #agf ,zeitsch4 anorg4 ,chem4 #aijb1 #cb1 #a4 ,illustration3 ,,fig4 #e4--;,,helical ,,representation ,,of ,,the ,,periodic ,,law ,electropositive ,elements1 above plane of paper1 black letters on white ground4 ,electronegative ,elements1 below plane of paper1 white letters on black ground4 ,intermediate ,elements1 in plane of paper1 black letters on sectioned ground4 ,illustration3 ---------------------------------------- ----------------- ,group ,,iii4 ,,iv4 ,v4 ,,vi4 ,,vii4 ,,viii4 ,a ,b,a ,b,a ,b,a ,b,a ,b ---------------------------------------- ----------------- ,series #f,yt ,zr ,cb ,mo ,ru ,rh ,pd #g ,in ,sn ,sb ,te ,i ---------------------------------------- ----------------- #h,la ,ce ,pr ,nd ,sa ,eu #i ,gd ,tb ,dy ,ho ,er,tm,yb ---------------------------------------- ----------------- #aj,lu ,ta ,w ,os ,ir ,pt #aa ---------------------------------------- ----------------- ,,fig4 #f4--,,part ,,of ,,the ,,periodic ,,table1 ,,showing ,,the ,,positions ,,assigned ,,to ,,the ,,rare ,,earth ,,elements ,,by ,,brauner ,,in #aijh ,brauner's conception is also in accord with the physical properties of the elements and their compounds4 ,these vary continuously throughout the group1 and show nowhere the sudden transitions which are characteristic of other series in the table4 ,benedicts#agg has collected all the data bearing on the atomic volumes1 and finds that those also vary continuously1 with rise in the atomic weights1 within quite small limits1 all lying between the values for barium and tantalum4 ,in face of all the evidence furnished by physical and chemical properties1 however1 ,brauner#agh has recently reverted to an idea which he put forward in #ahha1 according to which lanthanum and cerium are placed as usual in ,groups ,,iii and ,,iv1 series #h1 whilst the other elements are distributed in order throughout the remaining groups1 as shown in ,fig4 #f4 #agg ,zeitsch4 anorg4 ,chem4 #aijd1 #ci1 #da4 #agh ,monats4 #ahha1 #c1 #a2 ,zeitsch4 ,elektrochem4 #aijh1 #ad1 #ebe4 ,in support of this arrangement1 he quotes the fact that some of the elements appear to be able to form higher oxides in the presence of other oxides1 which act as oxygen carriers 7see pp4 #agd1 #agg-h71 though these higher oxides are certainly not salt-forming4 ,he also deduces1 from the rates of hydrolysis of the sulphates1 that the elements fall into two parallel series1 according to the strengths of the hydroxides as bases1 on which ground he justifies the distribution throughout series #h and #i4 ,there can be no doubt1 however1 that this disposition is far less in accordance with the behaviour and properties of the rare earth elements than is the first arrangement1 which places them in a transition zone between barium and tantalum2 it is impossible1 for example1 to reconcile the properties of praseodymium with those of columbium and tantalum1 or to find the slightest analogy between neodymium and molybdenum or tungsten1 as the second arrangement requires4 ,the analogy of the rare earth group to the elements of ,group ,,viii has been pointed out by many authors4#agi ,on the ground that the rare earth elements cannot be spread over the table in series #h-aj1 ,steele#ahj favours the early classification of ,thomsen1 according to which the elements are divided into three groups4 ,the first1 corresponding to ,groups ,i and ,,ii of ,mendelejeff's table1 consists of two sub-groups1 each containing seven elements#aha2 the second1 corresponding to the first two long series of the periodic table1 has two sub-groups1 each of seventeen elements1 of which the first and last seven are analogous--these elements fall into the same groups in the periodic table--whilst the middle three are interperiodic4 ,these interperiodic elements are those which ,mendelejeff places in ,group ,,viii4 ,the third division consists of one 7or two7 group7s7 of thirty-one elements2 here again1 the first and last seven are analogous1 whilst the interperiodic elements1 which are seventeen in number1 include the rare earth metals4 #agi ,compare ,biltz1 ,ber4 #aijb1 #ce1 #efb4 #ahj ,chem4 ,news1 #aija1 #hd1 #cde4 #aha ,the inert gases are not included4 ,steele's idea has been extended by ,werner1#ahb who has drawn up a table to illustrate it4 ,in this classification1 the elements are arranged in order of atomic weight1 but arbitrary gaps are left in such a way that similar elements may fall into the same vertical columns1 as in the periodic table4 ,the arrangement has the advantage that the interperiodic elements1 consisting of the rare earth elements and the elements placed in ,group ,,viii of the periodic table1 here do fall in the middle of their respective periods1 but it has several drawbacks1 and does not represent the transition of properties from element to element so well as the helical representation of the periodic table1 which brings out most clearly the true relations between the elements1 and the anomalous position of the rare earth metals4 #ahb ,ber4 #aije1 #ch1 #iad4 ,mention must be made at this point of the theory of #8,meta-elements' put forward in #ahhh by ,sir ,william ,crookes4#ahc ,from his work on the cathode luminescence of some of the oxides 7see next chapter71 that author was led to the conclusion that several of the then-accepted rare earth elements1 notably samarium and yttrium1 were in reality heterogeneous1 consisting of large numbers of very closely related bodies1 differing so very slightly in properties that only the most refined methods could perceive the variations2 for these he proposed the name ,meta-elements4 ,though it has been proved that the differences observed by ,crookes in the luminescence spectra were really due to the presence of very small quantities of impurities1 his paper is of great interest1 in that it contains a theory of evolution of the elements1 and postulates the possibility of their decay4 ,modern developments in radioactivity have not only lent a curious force to these speculations1 but even support his contention that a chemical element1 in the ordinary sense of the word1 is not necessarily homogeneous4#ahd ,in the field of the rare earths1 also1 the homogeneity of elements is even now continually being called into question 7see ,thulium1 p4 #bjd74 ,in any case1 we have in the rare earth elements a series of bodies in which the change of properties from one member to another--and the consequent possibility of easy separation--is so very slight1 and so far without parallel in the whole field of chemistry1 that we are at least justified in asking whether some extension of our ordinary conception of an element is not required4 #ahc ,trans4 ,chem4 ,soc4 #ahhh1 #ec1 #dhg4 #ahd ,see ,soddy1 ,the ,chemistry of the ,radio-,elements1 ,part ,,ii41 ,introduction4 ,,chapter ,x ,,general ,,methods ,,of ,,separation ,the chemist who sets out to prepare a pure compound of a rare earth element is faced by a great difficulty4 ,the rare earth compounds occur in nature1 as one might expect from their great similarity1 as mixtures of very complex composition4 ,after the relatively simple separation from foreign elements has been accomplished1 the enormously greater difficulty of separating the elements from one another has to be encountered4 ,so great is this difficulty1 by reason of the fact that1 with the sole exception of cerium1 the elements show no variation in property sufficient to allow of the use of ordinary analytical methods1 that even at the present day it is extremely doubtful if all the elements in the yttrium group are known to us4 ,the methods which can be adopted in attempting a separation are of two kinds4 ,the first includes those processes which take advantage of the gradual variation in basic strength of the hydroxides as the atomic weight changes2 the most important of these are fractional precipitation of the hydroxides1 and fractional decomposition of the nitrates4 ,fractional precipitation of the hydroxides is generally effected by gradual addition of ammonia1 soda1 magnesia1 or other base1 to a solution of the mixed salts2 such a solution may also be digested with the oxides obtained by ignition of another fraction of the rare earth compounds4 ,if the digestion be sufficiently complete1 the precipitate in each case will be richer in the less basic hydroxides1 whilst the solution will be richer in the salts of the more electropositive elements4 ,the fractional decomposition of the nitrates is based on the fact that when a mixture of the salts is heated gradually1 the nitrate of the least positive element begins to decompose first4 ,the temperature is maintained for some time at the point at which decomposition begins2 when nitrous fumes cease to be evolved the mixture is cooled1 and extracted with water or dilute acids4 ,the insoluble portion--basic or superbasic nitrate 7see p4 #abh7--will then be richer in the less electropositive elements2 the solution is evaporated1 and the solid so obtained subjected to a somewhat higher temperature1 and the process repeated several times4 ,in this way1 a series of fractions is obtained1 in which the elements tend to distribute themselves in order of electropositive character4 ,by a sufficient number of systematic repetitions of such steps1 the elements may eventually be obtained in the form of compounds of approximate purity1 which may then be refined by one of the methods of the second kind described below4 ,experience has shown1 however1 that a quicker and more complete separation may generally be effected by combining two or more methods of separation2 one method will give the best separation up to certain limits1 but then becomes much less valuable2 the separation at this point is therefore taken up by another process4 ,a process depending on differences of basic strength of the hydroxides is generally supplemented by a method of the second class1 i4e4 a process of fractional crystallisation2 where the basicity method is not used 7as1 for example1 in most of the recent processes for separation of the cerium elements71 two or more different methods of fractional crystallisation will supplement one another4 ,the methods of the second class1 which are processes of fractional crystallisation1 depend on the differences in solubility which are observed in analogous compounds in passing from one member of the group to another4 ,the value of these methods1 as opposed to the methods depending on differences in basic strength1 was clearly shown by ,auer von ,welsbach1 who in #ahhe succeeded in resolving ,mosander's #8,didymium' into two new elements1 praseodymium and neodymium1 by fractional crystallisation of the ammonium double nitrates2 since that date1 much attention has been devoted to the task of finding rare earth compounds which will lend themselves to such processes4 ,the method is extremely laborious1 and may involve several thousand recrystallisations1 in consequence of the generally very slight differences of solubility1 and the ease with which the rare earth compounds1 being almost always isomorphous with one another1 form mixed crystals4 ,whilst the method of fractional crystallisation has come into general use for the separation of one element from another only within the last thirty years1 processes for the separation of the cerium group from the yttrium elements1 depending on differences of solubility1 have long been known and used4 ,the most important of these1 the double sulphate method1 depends on the fact that the potassium double sulphates of the cerium metals are almost insoluble1 whilst those of the terbium group are sparingly1 and of the yttrium group readily soluble in a concentrated solution of potassium sulphate4 ,the cerium elements may be thus completely removed from a solution of mixed salts by addition of a crust of potassium sulphate crystals1 or of an hot concentrated solution of the same reagent4 ,in other cases1 e4g4 in the double carbonate and double oxalate processes1 separation is effected by taking advantage of the greater tendency to the formation of double salts possessed by the yttrium metals4 ,in effecting a separation of closely related bodies by fractional processes1 in which a large number of repetitions of the same operation are necessary1 only the most careful and systematic procedure can avoid much waste of valuable material2 in these processes1 the object of the chemist is to obtain pure end fractions1 whilst keeping the middle fractions as small as possible4 ,one method of procedure generally adopted is illustrated in ,fig4 #g1 which represents a fractional crystallisation of a mixture of four or five substances1 1 1 444 2 the separations being usually conducted in such a way that subgroups of three1 four or five elements are first obtained1 these being then further fractionated to obtain the pure elements4 ,in the diagram1 crops of crystals are represented by crosses1 the mother-liquors by circles2 for the sake of illustration1 the process is made to appear as simple as possible4 ,illustration3 ,,fig4 #g ,the mixture is dissolved up1 and allowed to crystallise2 the crystals are filtered off1 the filtrate concentrated1 and a second crop obtained2 this is repeated until five or six crops of crystals have been obtained4 ,these1 with the mother-liquor1 constitute series ,a4 ,the first fraction is now recrystallised2 it yields a crop of crystals1 fraction #a of series ,b1 and a mother-liquor1 which is added to fraction #b of series ,a1 as indicated by the dotted arrow and circle2 on recrystallisation of this mixture1 a crop of crystals1 fraction #b of series ,b1 is obtained1 together with a mother-liquor1 which is recrystallised with fraction #c of series ,a4 ,in this way1 by continued repetition1 series are obtained1 of which each contains one fraction more than its predecessor2 the least soluble constituent is thus concentrated in the fractions represented on the left of the diagram1 whilst the most soluble accumulates in the mother-liquors4 ,after a greater or smaller number of series have been traversed1 according to the differences in solubility1 the end fractions in each series will be pure4 ,these are no longer fractionated1 and the number of fractions in each series begins to diminish1 as shown on the diagram4 ,the middle fractions will contain the compounds of intermediate solubility2 these may be separated by further fractionation on the same lines1 or may perhaps be better treated by a different or modified process4 ,in a modification of the method1 each fraction of series ,a is recrystallised separately1 yielding a crop of crystals1 and a mother-liquor2 series ,b is then built up by adding to the crystals from fraction #b the mother-liquor from fraction #a1 to the crystals from fraction #c the mother-liquor from fraction #b1 and so on2 the fractions in this series are then recrystallised separately1 and the third series built up by the similar combination of the crystals and mother-liquors4 ,similar systematic methods of procedure must be adopted in working out any method of fractional separation2 it can at once be seen that where1 as in the rare earth group1 only small variations in properties exist1 much time and care must be expended1 if pure products are required4 ,since the development of the methods of spectrum analysis1 the difficulty of testing the efficiency of a method of separation1 and of examining the purity of the products obtained1 has been greatly lessened4 ,the only reliable test at the disposal of the earlier chemists was the determination of the equivalent weight1 which still constitutes an important check on the modern methods4 ,some account of the methods available for the control of the methods of separation is essential in a general account of the rare earths2 but before describing these1 it will be convenient to give a short description of the methods used in the extraction of the elements from the rare earth minerals4 ,,extraction ,,of ,,the ,,rare ,,earths ,,from ,,minerals ,with the exception of those containing large proportions of columbium1 tantalum1 and titanium1 the rare earth minerals are easily decomposed by acids4 ,the silicates1 as a general rule1 can be satisfactorily treated with hydrochloric acid in the ordinary way1 but for large quantities1 the use of sulphuric acid is more desirable4 ,the more refractory minerals are completely decomposed by fused alkali hydrogen sulphate2 sodium bisulphate is more suitable for this purpose than the potassium compound1 the sodium double sulphates of the rare earth elements being more soluble than the potassium salts4 ,hydrofluoric acid also attacks the refractory minerals very readily2 the rare earths1 in this case1 are left as the insoluble fluorides4 ,after decomposition with sulphuric acid or bisulphate1 the cold residue is extracted with water1 the rare earth sulphates or double sulphates being removed in solution4 ,digestion with nitric acid may be necessary at this stage1 if titanium1 columbium1 etc41 are present2 after filtration1 the solution is evaporated to dryness1 and the residue extracted with dilute hydrochloric acid4 ,the solution is saturated with sulphuretted hydrogen to remove lead1 copper1 bismuth1 molybdenum1 etc41 and treated in the usual way with ammonium chloride and ammonia4 ,the precipitate is washed1 and dissolved in hydrochloric acid1 the solution heated to about #fj1 and the rare earths precipitated by addition of excess of oxalic acid1 which holds in solution any zirconium which may be present4 ,in the presence of phosphates1 e4g4 in the treatment of monazite or xenotime1 the precipitate of oxalates should be ignited to the oxides1 these dissolved in acid1 and a second precipitation with oxalic acid effected2 this treatment is necessary to remove phosphoric acid completely4 ,preliminary examination of the earth mixture4--,before a method of separation can be decided upon1 some knowledge of the composition of the mixture to be treated must be obtained4 ,the nature of the mineral used for the extraction will1 as a rule1 afford useful information4 ,it is known that in some minerals the cerium group1 in others the yttrium group1 predominates more or less completely2 certain minerals1 also1 are known to be rich in elements of one or another subgroup4 ,an approximate knowledge of the relative proportions of the cerium1 terbium1 and yttrium groups will be afforded by a rough double sulphate separation2 thorium1 zirconium1 and scandium come down with the cerium earths4 ,for approximate separation1 ,urbain#ahe proposes the use of the ethylsulphates4 ,the yttrium elements can be quickly separated in an approximate manner by fractional precipitation of the hydroxides with magnesia4 ,the successive fractions obtained by these methods are examined spectroscopically2 from the results1 the composition of each1 and so of the original mixture1 may be roughly deduced4 #ahe ,ann4 ,chim4 ,phys4 #aijj1 vii41 #ai1 #ahd4 ,,the ,,spectrum ,,examination ,in no department of chemistry have the methods of spectrum analysis proved of more value than in the field of the rare earths4 ,they provide the chemist with a means of following and controlling his processes of separation which is far more delicate and decisive than the older method of determining the equivalent weight4 ,whilst the examination of emission spectra1 and especially of arc spectra1 is of decisive value in every case1 it has the disadvantage of requiring delicate and complicated apparatus and great experimental skill2 wherever possible1 therefore1 the examination of the absorption spectra is preferred1 though this is useful only for a few of the elements1 and varies considerably with the conditions employed4 ,the ,absorption ,spectra4--,absorption in the visible region of the spectrum is observed only with those rare earth compounds which are coloured1 and is of value1 therefore1 chiefly for identification in the case of praseodymium and neodymium among the cerium elements1 and of erbium among the yttrium metals2 these give characteristic absorption bands1 even in dilute solution4 ,the absorption spectra of the rare earth compounds are highly characteristic1 the bands being well defined and sharply bounded1 whereas coloured compounds of the common elements show general absorption1 or at best diffuse bands1 under the same conditions4 ,in observing an absorption spectrum1 the light from a ,nernst lamp1 or incandescent burner1 is passed through a layer of a suitable solution of the coloured compound1 of known concentration and thickness1 and after collimation is analysed by a suitable prism2 the spectrum is observed by a telescope in the ordinary way4 ,where accurate readings are not required1 as1 for example1 in testing for the presence or absence of a particular element1 the position of the bands may be read to a sufficient degree of accuracy by means of a scale1 the image of which is adjusted to coincide with the spectrum as seen through the eyepiece2 but in mapping a spectrum accurately1 more refined methods must of course be used4 ,the photographic method1 in which a photograph of the spectrum is taken on a plate which bears1 for purposes of measurement1 a comparison spectrum of known lines1 is very convenient for examining the absorption in the violet and ultraviolet regions4 ,the intensity1 and to some extent also the position1 of bands in an absorption spectrum may vary considerably1 according to the conditions employed4 ,of the various factors which must be considered1 the concentration of the solution1 the thickness of the layer used1 the nature of the solvent1 and of the acid radicle1 and the presence of other earths are the most important4 ,the concentration of the solution1 and the thickness of the layer1 which together constitute the ,optical ,density1 must be so adjusted that the absorption is neither too strong nor too weak2 in the first case the sharp bands tend to merge into broad diffusion areas1 and details are obscured1 whilst in the second case the presence of coloured compounds which do not show strong absorption bands may be overlooked4 ,the nature of the acid radicle has considerable influence on the position of the absorption maxima1 the general rule being that the bands are shifted towards the red end of the spectrum as the molecular weight of the compound used increases4 ,naturally1 also1 the nature of the solvent has an important effect1 all the usual phenomena which must be considered in the measurement of the physical properties of substances in solution coming into play2 electrolytic dissociation1 hydration1 dissociation and the formation of complexes1 for example1 are all important factors4 ,the presence of colourless earths has also been found to cause important differences4 ,it follows1 therefore1 that for the chemist1 the absorption spectra can be considered as a valuable aid only in detecting the presence or absence of the three elements which give the strongest and most characteristic absorption bands1 viz4 praseodymium1 neodymium1 and erbium1 and that conclusions regarding the quantitative composition of mixtures must be drawn with the utmost caution4 ,the ,emission ,spectra3 ,spark ,spectra4--,the factors which tend to limit the value of the absorption spectra for analytical purposes1 for the most part disappear when the emission spectra are employed4 ,in the case of the spark spectra1 indeed1 great differences are observed according to the conditions and method of experiment2 but the arc spectra are practically invariable under all conditions1 and hence they constitute the ultimate test in all cases4 ,the spark spectra are observed when one terminal--the cathode--of an induction coil is embedded in the oxides to be examined1 and the discharge then passed4 ,the discharge is also frequently passed between platinum poles partly immersed in a strong solution of a salt of the element under examination2 a form of apparatus very suitable for this method of observation has been described by ,sir ,w4 ,crookes4#ahf ,the spectra so obtained are in a high degree characteristic1 but they vary very considerably with the form and dimensions of the coil1 the length and cross-section of the wires1 the potential difference employed1 and so on4 ,an entirely new spectrum also is obtained in many cases by mere reversal of the current2 under these conditions1 a phosphorescent appearance is observed1 the spectrum of which--reversed spark spectrum of de ,boisbaudran--has been found in many cases to resemble the cathode luminescence spectra of ,crookes4 #ahf ,proc4 ,roy4 ,soc41 #aijc1 #gb1 #bie4 ,the ,arc ,spectra4--,the final criterion of purity in the examination of a rare earth element is in almost all cases the arc spectrum4 ,since for some of the elements1 especially in the yttrium group1 the entire spectrum has not yet been accurately mapped out1 spectra are generally observed frequently throughout the course of a fractionation2 by this means1 the separation can be followed by the disappearance of some lines1 and the appearing or strengthening of others1 and such examinations have led occasionally to the discovery of new elements 7see1 for example1 under ,separation of ytterbium earths1 p4 #bje74 ,such determinations1 however1 require much time and extensive and complicated apparatus4 ,carbon electrodes are generally employed1 and it is immaterial in this case which is the anode1 and which the cathode4 ,the lower carbon is hollowed out1 and the space filled with the oxide or sulphate of the element or mixture to be examined2 or the electrode may be impregnated with a concentrated solution of a salt4 ,the light is examined by means of a diffraction grating1 and the spectrum photographed on a plate which bears a comparison spectrum for measurement4 ,the lines are most numerous in the violet and ultraviolet regions1 and the most characteristic spectra are given by the colourless earths4 ,the method is naturally more delicate for some elements than for others2 the great persistency of the scandium line #cfacihd1 for example1 was found very valuable by ,crookes and by ,eberhard in the examination of various rocks and minerals for that element1 whilst other intense and persistent lines have served for the detection of various rare earth elements in the sun and many stars4 ,the ,cathode ,luminescence ,spectra4--,the phenomenon of cathode luminescence1 which was observed and very fully investigated by ,sir ,william ,crookes1 and which led that author to his theory of ,meta-elements1 is one of the greatest scientific interest4 ,crookes observed that certain of the rare earths1 when subjected to the action of cathode rays in a vacuum tube1 exhibit a brilliant phosphorescence1 which1 when examined by the spectroscope1 show characteristic spectra1 which differ greatly for fractions of apparently identical chemical composition1 and are otherwise distinguishable by physical properties4 ,the researches of ,lecoq de ,boisbaudran1 and the more recent work of ,baur and ,marc1#ahg have shown that this luminescence is observed when a small quantity of a coloured earth is present with a very large quantity of a colourless earth1 the maximum phosphorescence being produced by about #a per cent4 of the coloured earth1 or #8phosphorogen4' ,the question has recently been very fully examined by ,urbain4#ahh ,he shows that the sensitiveness of the phenomenon is so great that it cannot be employed for the ordinary purposes of chemical analysis1 one part in a million of the phosphorogen being sufficient to cause a clearly perceptible luminescence in a pure colourless oxide4 #ahg ,ber4 #aija1 #cd1 #hgh4 #ahh ,ann4 ,chim4 ,phys4 #aiji1 viii41 #ah1 #bbb2 see also ,introduction l'tude de la ,spectrochimie1 pp4 #ade et seq4 ,the ,magnetic ,susceptibility4--,the fact that the rare earths differ very considerably from one another in their magnetic properties has been known for several years1#ahi and has recently been employed by ,urbain and ,jantsch#aij as a means of identification1 and a test of purity1 and for following processes of fractionation4 ,the magnetic susceptibility reaches a minimum at samarium1 and rises very sharply on either side of that element1 so that the presence of the closely related elements1 neodymium on the one side1 and europium and gadolinium on the other1 which differ only very slightly from samarium in atomic weight and solubility1 can easily be detected by this means4 ,the property is highly additive1 and can be used1 therefore1 to estimate the relative proportions of two oxides in a mixture2 the determinations are said to be easily and quickly carried out4 #ahi ,see ,meyer1 ,monats4 #ahih1 #bj1 #cfi and #gic4 #aij ,compt4 rend4 #aijh1 #adg1 #abhf2 see also ,urbain1 ibid41 #aiaj1 #aej1 #iac4 ,when the elements are considered in order of atomic weight1 the coefficient reaches a maximum at neodymium in the cerium group1 and again at dysprosium 7or holmium7 in the yttrium group3--#aia ,coefficient of magnetisation ,element4 ,atomic ,weight4 for the oxide4 x #aj ,scandium #dda -#jje ,yttrium #hij -#jad ,lanthanum #acij -#jah ,neodymium #addc #cce ,samarium #aejd #fe ,europium #aebj #cce ,gadolinium #aegc #afa ,terbium #aeib #bcg ,dysprosium #afbe #bij #aia ,see ,urbain and ,jantsch1 loc4 cit42 the values for lanthana1 scandia1 and yttria were determined by ,wedekind 7see ,meyer and ,wuorinen1 ,zeitsch4 anorg4 ,chem4 #aiac1 #hj1 #g74 ,erbium1 thulium1 ytterbium1 and lutecium appear in descending order at the end of the series1 but no figures are given4 ,the most interesting application of the property has been ,urbain's discovery of the new element ,celtium 7see p4 #bjg74 ,,the ,,equivalent ,,weight ,,determination ,the determination of the mean equivalent weight1 which was for the earlier chemists the only reliable method of controlling their fractionations1 is still of considerable importance for this purpose1 especially in the yttrium group1 in which the differences in atomic weights are more considerable than among the cerium metals4 ,great importance1 moreover1 still attaches to these determinations1 since they serve to fix the atomic weights2 save that the methods used in an atomic weight determination are somewhat more elaborate and refined than those used when it is desired merely to test a fractionation1 the same processes apply in both cases4 ,the methods which have been most commonly used are those based on a determination of the ratio ,r,o 3 ,r7,,so71 and these are of two kinds1 the synthetic and the analytical4 ,the first1 in which a known weight of the oxide is converted into the sulphate1 has been most used for the most strongly basic oxides1 since with these it is difficult to remove the last traces of sulphuric anhydride from the oxide by heat4 ,the oxides are best obtained from the oxalates1 which are precipitated from an acid solution of the nitrates1 washed thoroughly with water1 alcohol and ether in succession1 dried1 and ignited in a tarred platinum crucible4 ,the oxide is best dissolved in dilute hydrochloric or nitric acid on the waterbath1 a slight excess of sulphuric acid being added only when a clear solution has been obtained2 the liquid is then heated gradually to #cjj1 and finally in the electric furnace at #dej-eej until constant in weight4 ,if sulphuric acid be added directly to the weighed oxide1 particles of the latter may become completely coated with the insoluble sulphate1 and so escape the action of the acid4 ,in the analytical method1 a known weight of sulphate is ignited to the oxide1 and weighed as such4 ,this method is most suitable for the less basic members of the yttria earths1 of which the sulphates can be completely decomposed without difficulty at a red heat4 ,by the use of the microbalance1 a sufficiently accurate determination can be carried out by either of these methods in little more than half an hour1 as the chemical changes are exceedingly rapid where only small quantities are employed1 and no time is required to allow the vessels and solids to cool4 ,using the microbalance1 ,brill#aib has carried out a series of experiments to determine the limits of temperature within which the various steps of the process should be carried out4 ,he finds that a temperature of #djj-eej is required to decompose the last traces of acid sulphate1 and give the pure neutral sulphate4 ,between the temperatures of #hej and #iej1 basic salts are formed1 from which the last trace of sulphuric anhydride is expelled at #ijj-aaej2 the precise temperature required in each case depends1 of course1 on the basic strength of the oxide in question4 #aib ,zeitsch4 anorg4 ,chem4 #aije1 #dg1 #dfd4 ,the determination of equivalents by means of the ratio ,r,o 3 ,r7,c,o71 has been brought to a high degree of accuracy by ,brauner4#aic ,a weighed quantity of the carefully prepared oxalate is ignited1 with suitable precautions1 to the oxide1 in a tarred platinum crucible4 ,a second weighed specimen of the same oxalate preparation is dissolved in dilute sulphuric acid1 and titrated at #fj with permanganate1 which is standardised against pure ammonium oxalate4 #aic ,ibid4 #aijc1 #cd1 #ajc1 #bjg4 ,of the methods of volumetric analysis which have been proposed1 that put forward by ,feit and ,przibylla appears to be the most suitable4 ,a convenient quantity of oxide1 which has been ignited until constant in weight1 is dissolved by gently heating with a known excess of ,n_/#b sulphuric acid1 in a conical flask of ,jena glass4 ,the excess of acid is titrated with ,n_/#aj sodium hydroxide1 using methyl orange as indicator4 ,this method1 which has the advantages of ease and quickness1 is very reliable1 if suitable precautions are taken1 in the case of the more strongly basic oxides2 but with the least strongly basic members of the yttria group1 the erbia and ytterbia oxides1 the end point is not very sharp1 whilst with the weakly basic scandia1 the method breaks down entirely4#aid #aid ,zeitsch4 anorg4 ,chem4 #aije1 #dc1 #bjb2 #aijf1 #ej1 #bdi4 ,,chapter ,,xi ,,the ,,cerium ,,group--,,cerium ,the extraction of the rare earth elements from minerals1 by which they are obtained in the form of the oxalates1 and the methods of bringing these into solution1 have already been described4 ,from the solution1 before any separation of the rare earths is attempted1 thorium should be removed2 for this purpose1 any of the methods described under estimation of thorium 7see p4 #bhf7 may be used1 the most convenient being the peroxide precipitation of ,wyrouboff and ,verneuil4 ,the solution is then treated with potassium sulphate until the absorption bands of didymium 7praseodymium and neodymium7 can no longer be observed1 or appear only very faintly1 when a layer of the solution is examined with a spectroscope2 the precipitate then consists of the potassium double sulphates of the cerium with some of the terbium elements4 ,if the mixture is very rich in the cerium elements1 and correspondingly poor in the yttrium elements--as1 for example1 the mixture of earths obtained from monazite--,drossbach#aie recommends a preliminary separation by means of the double carbonates2 the double sulphate method may then be employed to remove the last of the yttrium and most of the terbium elements4 ,the sparingly soluble double sulphates of the cerium metals may be transformed into the hydroxides by digestion with potassium hydroxide1 and these taken into solution1 after washing1 by hydrochloric or nitric acid4 #aie ,ber4 #aijj1 #cc1 #cejf4 ,cerium1 ,ce #adjbe ,of all the rare earth elements1 cerium1 by virtue of its property of forming ceric salts corresponding to the dioxide ,ce,o1 is the one most easily separated and obtained in the pure state4 ,in those compounds in which it is tetravalent1 cerium functions as a much less strongly electropositive element than in the cerous compounds1 and all the methods of separation are based on this fact4 ,mosander1 who first demonstrated that the old #8ceria' was a mixture1 separated the element by treating a suspension of the hydroxides in potassium hydroxide with chlorine2 yellow ceric hydroxide remains undissolved1 whilst the other elements go into solution as the chlorides and hypochlorites4 ,this method was extensively used until quite recently2 it has the advantage of separating the cerium completely1 but the product is very impure1 and several repetitions are required to give good results4 ,the basic nitrate method1 which is now used on the commercial scale in extracting cerium from monazite 7see p4 #bhd71 is also due to ,mosander1 though it has been employed subsequently by many workers4 ,several methods take advantage of the ease with which the ceric salts1 as compared with salts of the trivalent elements1 may be hydrolysed4 ,brauner#aif dissolves the oxides in nitric acid1 and after removal of excess of acid1 boils with a large volume of water--basic ceric nitrate is thrown down1 the other elements remaining in solution as nitrates4 ,the precipitate is redissolved1 and the process repeated until the cerium is found spectroscopically to be free from didymium4 ,the hydrolysis of the ceric salt may be effected more quickly and completely by the addition of ammonium sulphate or magnesium acetate4#aig ,james#aih boils the solution of the nitrates with potassium bromate1 keeping the whole neutral by addition of powdered marble2 the cerium is completely and very quickly precipitated as basic nitrate4 #aif ,trans4 ,chem4 ,soc4 #ahhe1 #dg1 #hgi4 #aig ,meyer and ,koss1 ,ber4 #aijb1 #ce1 #fgb4 #aih ,j4 ,amer4 ,chem4 ,soc4 #aiab1 #cd1 #geg2 this paper gives a complete scheme for a full separation of all the elements4 ,an interesting method is due to ,koppel#aii2 the oxides are dissolved in a solution of hydrogen chloride in methyl alcohol1 and treated with pyridine1 when the sparingly soluble double chloride1 7,c,h,,nh7,ce,cl1 separates1 and may be obtained pure by recrystallisation from alcohol and ether4 ,the permanganate method of ,drossbach1 which is used on the commercial scale1 is described on p4 #bhe4 #aii ,zeitsch4 anorg4 ,chem4 #ahih1 #ah1 #cje4 ,the cerium compounds obtained by these methods are purified by transformation into the anhydrous sulphate1 which is dissolved in ice-water2 when this solution is allowed to come slowly to room temperature1 the pure octohydrate separates4 ,pure cerium salts should show no trace of absorption when concentrated solutions are examined spectroscopically2 on ignition1 the oxide obtained should be almost colourless1 having at most a faint yellow tinge4 ,a reddish or brownish-red shade indicates the presence of praseodymium4 ,an arc spectrum examination will generally show the presence of lanthanum1 which occurs in traces even in the most carefully purified cerium preparations4 ,the preparation and properties of metallic cerium have already been described 7see p4 #aad72 for an account of the pyrophoric alloys1 see p4 #cad4 ,,the ,,cerous ,,compounds ,the salts of trivalent cerium are very similar to those of the other rare earth elements1 and a detailed description of them is therefore unnecessary4 ,the sesquioxide1 ,ce,o1 cannot be obtained by ignition of the oxalate1 nitrate1 or other similar salt1 since these decompose at high temperatures with formation of the dioxide1 ,ce,o4 ,it has been prepared by the reduction of the dioxide with calcium2#bjj it has a great affinity for oxygen1 and readily absorbs the gas when exposed to moist air4 ,cerous hydroxide1 ,ce7,,oh71 obtained by addition of alkali to solutions of cerous salts1 has also strong reducing properties1#bja and can only be prepared and preserved when oxygen is carefully excluded4 ,it has been obtained as a perfectly white solid by the action of water on the carbide2#bjb when dried in an inert atmosphere1 it yields a perfectly white oxide4 ,in presence of air1 it darkens1 assuming a reddish-violet colour1 which passes into yellow as the oxidation becomes complete4 ,the oxidation proceeds more quickly in presence of potash or soda1 ceric hydroxide1 ,ce7,,oh71 being formed2 in presence of potassium carbonate1 however1 a dark-coloured peroxyhydrate is formed by autoxidation4 ,the colour so produced disappears on shaking if an #8acceptor' is present1 ceric hydroxide being left2 if the acceptor cannot reduce this1 the solution after shaking loses the power of re-forming the dark peroxide1 but if the acceptor can reduce the ceric compound to cerous hydroxide1 the solution after shaking regains the power of forming the peroxide which is a property of the lower hydroxide4 #bjj ,burger1 ,ber4 #aijg1 #dj1 #afeb4 #bja ,dennis and ,magee1 ,j4 ,amer4 ,chem4 ,soc4 #ahid1 #af1 #fdi2 also ,biltz and ,zimmerman1 ,ber4 #aijg1 #dj1 #digi4 #bjb ,damiens1 ,compt4 rend4 #aiac1 #aeg1 #bad4 ,cerous nitride1 ,ce,n1 has been prepared by ,moissan#bjc by the action of ammonia on the heated carbide2 it can also be obtained by heating the hydride in a stream of nitrogen4#bjd ,muthmann and ,kraft also state#bje that it can be prepared by heating metallic cerium in the gas1 the metal burning with the liberation of much energy in the form of heat and light2 but ,dafert and ,miklanz#bjf deny that it can be obtained in this way4 ,cerium nitride is a lustrous1 brass yellow to bronze coloured solid1 stable in dry air1 but at once attacked by moist air1 with evolution of ammonia1 and formation of the dioxide4 ,when moistened in air with a few drops of water1 the substance reacts violently1 becoming heated to redness4 ,alkalies and acids decompose it1 with formation of cerous compounds4 #bjc ,compt4 rend4 #aijj1 #aca1 #hfe4 #bjd ,dafert and ,miklanz1 ,monats4 #aiab1 #cc1 #iaa4 #bje ,annalen1 #aijb1 #cbe1 #bfa4 #bjf ,loc4 cit4 ,the sulphide1 ,ce,s1 has been prepared by ,biltz#bjg by heating the sulphate to a red heat in a current of sulphuretted hydrogen2 he describes it as a red powder4 ,the chloride1 ,ce,cl1 combines with ammonia with evolution of heat even at a temperature of -#hj4 ,five additive compounds are described2#bjh they are white powders1 decomposed by water4 #bjg ,ber4 #aijh1 #da1 #ccda4 #bjh ,barre1 ,compt4 rend4 #aiac1 #aef1 #ajag4 ,the solubility curve of the various sulphate hydrates has already been given 7see p4 #abe74 ,various double sulphates with ammonium sulphate1 and the sulphates of sodium1 potassium1 thallium and cadmium are known4 ,the cadmium double compound has the composition ,ce7,,so71,cd,s,o1#f;,h,o1 and is prepared by mixing solutions of the simple salts in presence of sulphuric acid4 ,many double nitrates have been prepared2 these are for the most part stable1 highly crystalline compounds1 easily soluble in water and alcohol4 ,with the nitrates of the common divalent metals1 cerous nitrate forms a series of double salts of the general formula #b;,ce7,,no71#c,r7,,no71#bd;,h,o1 where ,r ,mg1 ,mn1 ,co1 ,ni1 or ,zn2 these form an isomorphous series1 crystallising in the hexagonal system4 ,the acetylacetone compound melts at #aca-acb4 ,in the presence of hydrogen peroxide in the cold1 ammonia throws down from solutions of cerous salts a reddish-brown peroxyhydrate1 ,ce7,,ooh77,,oh71#bji which on heating loses oxygen1 and yields ceric hydroxide4 ,the reaction is very delicate1 and may be used as a test for cerium4 ,if the precipitate be treated with acids in the cold1 ceric salts are first obtained1 but these are at once reduced1 in the acid solution1 by the hydrogen peroxide formed1 so that cerous salts remain2 ceric salts may be obtained by first boiling the suspension of the peroxyhydrate and treating the ceric hydroxide so obtained with acids4 #bji ,pissarjewski1 ,zeitsch4 anorg4 ,chem4 #aijb1 #ca1 #cei4 ,,the ,,ceric ,,compounds ,the ceric salts are much more readily hydrolysed than the cerous salts1 and show a great tendency1 in dilute solution1 to pass over into the latter4 ,so great is this tendency that a solution of a ceric salt acts as if it were supersaturated with oxygen2 ceric sulphate1 for example1 in dilute solution slowly evolves oxygen1 whilst the chloride evolves chlorine4 ,in consequence of this behaviour1 ceric compounds have a very powerful oxidising action4 ,the ceric salts are yellow to red in colour2 their solutions are strongly acid1 owing to the ease with which the salts hydrolyse1 and on boiling deposit insoluble basic salts4 ,beside the methods which have already been mentioned1 ceric compounds may be prepared from cerous by oxidation with sodium peroxide1 bismuth tetroxide1 ammonium persulphate1 etc4 ,in electrolysis of cerous salts1 also1 ceric compounds are obtained at the anode4 ,ceric hydroxide1 ,ce7,,oh71 is obtained as a gelatinous yellow precipitate on the addition of alkali to a solution of a ceric salt1 or by the oxidation of cerous hydroxide4 ,the freshly prepared precipitate dissolves in nitric acid with a reddish colour2 hydrochloric acid reduces it1 with evolution of chlorine1 and formation of cerous chloride1 whilst sulphuric acid dissolves it with partial reduction1 oxygen being evolved4 ,if a solution of a ceric compound be dialysed for some days1 a clear neutral solution is obtained1 which contains the hydroxide in the colloidal condition2 by evaporation of the solution1 a gummy mass is obtained1 which dissolves again in water to a clear solution4 ,electrolytes rapidly cause coagulation4 ,cerium dioxide1 ,ce,o1 is obtained by the ignition of any salt of cerium with a volatile acid1 or by burning the element in oxygen2 the latter reaction produces a very intense and blinding light1 on account of which cerium compounds are often suggested for use in flashlight powders 7see p4 #cai74 ,the pure oxide should be almost white1 or at most a very faint yellow1 but the exact shade and appearance vary according to the method and temperature employed in preparation1 doubtless by reason of the possibility of different degrees of polymerisation4#baj ,the oxide can act as an oxygen carrier towards other substances1 notably towards other oxides of the rare earth group1#baa but the phenomena have not been fully elucidated4 ,in virtue of this property1 the dioxide has been proposed as a substitute for platinised asbestos in ,dennstedt's method for the combustion of organic bodies4#bab #baj ,see in this connection ,wyrouboff and ,verneuil1 ,compt4 rend4 #ahih1 #abg1 #hfc2 ibid4 #ahii1 #abh1 #eja2 and in ,la chimie des terres rares1 #8,confrences de la ,socit chimique de ,paris1' ,paris1 #aijc4 #baa ,see ,meyer and ,koss1 ,ber4 #aijb1 #ce1 #cgdj4 #bab ,bekk1 ,ber4 #aiac1 #df1 #begd4 ,the ignited oxide is soluble in nitric or hydrochloric acid only in presence of a reducing agent4 ,concentrated sulphuric acid converts it into ceric sulphate2 fused bisulphate attacks it more readily4 ,in the crystalline form1 obtained by fusing the amorphous form with borax1 or a suitable salt1#bac it is extremely resistant to acids and to alkalies4 #bac ,see1 e4g4 ,sterba1 ,ann4 ,chim4 ,phys4 #aijd1 viii41 #b1 #aic4 ,by heating the dioxide in a stream of hydrogen1 care being taken to exclude air1 a dark blue oxide1 of which the composition corresponds approximately to that required by the formula ,ce,o1 is obtained4#bad ,this substance has strong reducing properties2 when warmed in air1 it glows1 forming the dioxide1 and reduces carbon dioxide when heated in a current of that gas4 ,this intermediate oxide is said to correspond in composition to the violet hydroxide which is obtained as an intermediate product in the oxidation of cerous to ceric hydroxide1 and which is said to yield the blue oxide1 ,ce,o1 when dried in vacuo4 #bad ,sterba1 ,compt4 rend4 #aija1 #acc1 #bba2 ,meyer1 ,zeitsch4 anorg4 ,chem4 #aijc1 #cg1 #cgh4 ,the disulphide1 ,ce,s1 has been obtained by ,biltz#bae by prolonged heating of anhydrous cerous sulphate in a current of sulphuretted hydrogen at a dull red heat2 it is a dark1 yellowish-brown1 crystalline solid1 which on treatment with hydrochloric acid yields hydrogen persulphide4 #bae ,ber4 #aijh1 #da1 #ccda4 ,halogen salts4--,no halogen compounds are known in the free state1 except the fluoride1 ,ce,f1,h,o1 which was obtained by ,brauner as a yellowish-brown mass1 by the action of hydrofluoric acid on the hydroxide4 ,a double fluoride1 #b;,ce,f1#c,,kf1#b;,h,o1 was prepared by the same author by dissolving the hydroxide in potassium hydrogen fluoride2 it is insoluble in water4 ,by dissolving a ceric salt in concentrated hydrochloric acid1 a dark red solution is obtained1 which is believed to contain the unstable complex acid1 ,h,ce,cl2 this decomposes slowly in the cold1 more quickly on warming1 with evolution of chlorine1 and formation of cerous chloride4 ,several double compounds of ceric chloride with hydrochlorides of organic bases have1 however1 been obtained4 ,ceric sulphate1 ,ce7,,so71 is obtained by the action of concentrated sulphuric acid on the dioxide4 ,it is a deep yellow crystalline powder1 dissolving readily in water to a brown solution1 which has a strongly acid reaction2 on warming or diluting1 a basic sulphate separates4 ,the solution slowly evolves oxygen1 and therefore always contains cerous compounds4 ,on evaporation1 a cero-ceric acid sulphate of the formula ,h,ceiii,ceiv7,,so71#ab7ac 87,h,o first separates2 the hydrated sulphate ,ce7,,so71#d;,h,o1 being more soluble1 separates on further concentration4#baf ,the relative amounts of the two compounds obtained depends on the temperature and the concentration of acid in the solution2 if both these factors are kept low1 the almost pure hydrated sulphate can be at once obtained4 ,this separates in yellow crystals belonging to the rhombic system2 it is readily soluble in water4 ,the mixed acid salt is less soluble1 and forms orange prisms and needles1 which cling tenaciously to sulphuric acid4 ,other complex and double salts have also been obtained4 ,when1 for example1 silver nitrate is added to a warm solution of the sulphate in concentrated sulphuric acid1 a bright orange-yellow precipitate of the salt #aj;,ce7,,so71#f;,ag,,so is obtained4#bag #baf ,see ,meyer and ,aufrecht1 ,ber4 #aijd1 #cg1 #adj2 ,brauner1 ,zeitsch4 anorg4 ,chem4 #aijd1 #ci1 #bfa4 #bag ,pozzi-,escot1 ,compt4 rend4 #aiac1 #aef1 #ajgd4 ,neutral ceric nitrate is unknown4 ,a basic nitrate1 ,ce7,,no7,,oh1#c;,h,o1 is obtained in red crystals by evaporation of a solution of ceric hydroxide in strong nitric acid4 ,the solid is readily soluble in water1 forming a yellow1 acid solution1 which becomes paler by hydrolysis1 on warming or on standing4 ,the course of the hydrolysis is also indicated by the action towards acids1 and towards hydrogen peroxide4#bah ,a freshly prepared ceric salt1 on addition of acid1 becomes immediately much darker in colour1 whereas the colour change is very slow1 if considerable hydrolysis has occurred4 ,similarly1 hydrogen peroxide at once reduces a freshly prepared solution1 forming colourless cerous salts1 whilst if much hydrolysis has occurred1 deeply coloured higher oxidation products are at first formed1 and these lose their colour only slowly4 #bah ,meyer and ,jacoby1 ,zeitsch4 anorg4 ,chem4 #aija1 #bg1 #cei4 ,the double ceric nitrates#bai are a large and very important class of compounds2 they are the most stable of the ceric salts4 ,with nitrates of the monovalent metals1 ceric nitrate forms double nitrates of the type ,r,ce7,,no72 these are deep red hygroscopic substances1 crystallising in the monoclinic system1 readily soluble in water and alcohol1 but dissolving only sparingly in nitric acid4 ,the ammonium salt is important for the separation of cerium4 ,a series of double nitrates with the nitrates of manganese1 magnesium1 zinc1 nickel1 and cobalt has the general formula ,r,ce7,,no71#h;,h,o1 but these are much less stable in solution than the alkali double salts4 #bai ,meyer and ,jacoby1 loc4 cit4 ,,atomic ,,weight ,,of ,,cerium ,no less than twenty-eight separate determinations of the atomic weight of cerium have been carried out4 ,the earlier determinations are rendered unreliable by the almost certain presence of other elements1 and ,brauner#bbj has shown that some of the methods employed in later work give erroneous results4 #bbj ,trans4 ,chem4 ,soc4 #ahhe1 #dg1 #hgi2 also ,zeitsch4 anorg4 ,chem4 #aijc1 #cd1 #bjg4 ,a very careful determination was made by ,robinson in #ahhd4bba ,cerium oxalate was heated in a stream of dry hydrogen chloride1 mixed with carbon dioxide1 and the anhydrous chloride freed from traces of acid in a vacuum over chalk4 ,the weighed chloride was then dissolved in water1 and titrated with silver nitrate4 ,he obtained the value #adjbf2 recalculation from his data with the modern values for silver and chlorine give #adjai4 ,brauner points out that this result is too low1 since no account was taken of the solubility of silver chloride in water4 ,in the following year1 ,brauner#bbb determined the ratio ,ce7,,so7 3 #b;,ce,o1 and obtained the atomic weight #adjbb4 ,wyrouboff and ,verneuil#bbc in #ahig disputed ,brauner's work1 and as a result of several determinations gave the values #aciba1 #acidc1 and #aciej2 their determinations1 however1 varied very considerably1 and the work has been severely criticised by ,brauner4 ,in #aijc1 the latter author and ,batk#bbd obtained the values #adjba and #adjbg by the sulphate and oxalate methods respectively2 whilst in the same year1 using the same methods1 ,brauner#bbe obtained from three independent series of determinations the values #adjbe1 #adjbd1 and #adjbe4 #bba ,proc4 ,roy4 ,soc4 #ahhd1 #cg1 #aej4 #bbb ,loc4 cit4 #bbc ,compt4 rend4 #ahig1 #abd1 #acjj4 #bbd ,zeitsch4 anorg4 ,chem4 #aijc1 #cd1 #ajc4 #bbe ,zeitsch4 anorg4 ,chem4 #aijc1 #cd1 #bjg4 ,the ,international ,atomic ,weight ,committee have accepted the value #adjbe since #aijd4 ,,detection ,,and ,,estimation ,,of ,,cerium ,the detection of cerium in a mixture of earths is a comparatively simple matter1 as it has several distinctive reactions4 ,the brown colour of the peroxy-compounds has been suggested as a convenient test by several authors4 ,this may be observed when ammonia is added to a cerous salt in presence of hydrogen peroxide4 ,in the presence of a large excess of foreign earths1 very dilute ammonia should be added1 drop by drop1 with continuous shaking1 until a small permanent precipitate remains2 this will be rich in the weakly basic ceric hydroxide1 and on addition of the peroxide solution will show the colour clearly4#bbf ,for very small quantities of cerium1 the neutral solution is added to warm concentrated potassium carbonate solution1 and one or two drops of dilute hydrogen peroxide added to the clear liquid2 the yellow colour is then very characteristic4#bbg #bbf ,marc1 ,ber4 #aijb1 #ce1 #bcgj4 #bbg ,meyer1 ,zeitsch4 anorg4 ,chem4 #aijd1 #da1 #id4 ,biltz and ,zimmerman#bbh employ the reducing powers of cerous hydroxide2 ammoniacal silver nitrate is added to the neutral solution of the cerous salt1 and the mixture warmed4 ,dilute solutions 7#a-b mgms4 per litre7 give a brown colour1 concentrated solutions a black precipitate4 ,the oxidation of an ammoniacal solution of the tartrate by air or hydrogen peroxide1 by which an intense yellowish brown colour is developed1 has been recently suggested by ,wirth#bbi as a very delicate test for the element4 #bbh ,ber4 #aijg1 #dj1 #digi4 #bbi ,abstr4 ,chem4 ,soc4 #aiac1 #ajd1 ii4 #gab4 ,spectrum analysis4--,cerous salts show no absorption1 ceric salts general absorption of the violet end of the spectrum4 ,arc spectrum--see ,exner and ,haschek1#bcj ,eder and ,valenta1#bca and ,cooper4#bcb ,the emission spectrum of cerium is especially rich in lines2 for identification1 the following may be used3 #bcj ,die ,spektren der ,elemente1 etc41 ,leipzig and ,vienna1 #aiaa4 #bca ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aiaj1 #aai1 ,,iia1 #eca4 #bcb ,astrophys4 ,j4 #aiji1 #bi1 #ceb4 #daejaa #dahfgh #dbbbgh #dbifhh #dccgif #dchbcb #dchfie #ddfjdj #ddgieb #ddhgjf #debgea #debhfd #deciij #defbeb #degbde #deidaa #dfbhcc #eeabgb ,the estimation of cerium cannot be carried out accurately by gravimetric methods in the presence of other earths2 volumetric methods1 however1 will give reasonably accurate results1 if the necessary precautions are taken4 ,in ,bunsen's method the ignited oxides are treated with hydrochloric acid in presence of potassium iodide1 the iodine set free from the hydriodic acid by reduction of the cerium dioxide being estimated by means of sodium thiosulphate1 in the usual way4 ,this method gives very inaccurate results1 since in the presence of cerium dioxide1 other oxides of the group can be converted into higher oxides which will also liberate iodine under these conditions4 ,the most reliable method is that of v4 ,knorre4#bcc ,the solution to be estimated is acidified with sulphuric acid1 and oxidised by means of ammonium persulphate4 ,the excess of the oxidising agent having been destroyed by boiling1 the cooled solution is treated with a slight excess of hydrogen peroxide1 which reduces the ceric salt according to the equation3 #b;,ce7,,so7 ,h,o ,ce7,,so7 ,h,,so ,o ,the excess of hydrogen peroxide is then estimated by means of a dilute permanganate solution4 ,permanganate is itself reduced by the cerous salt formed1 but the action is so slow in acid solution at the ordinary temperature that the excess of peroxide can be accurately determined without unduly hurrying the titration4 ,in this form the method is generally employed for the estimation of cerium in monazite sands1 and in the incandescent mantle industry4 ,the greatest difficulty is the adjustment of the concentration of the sulphuric acid required4 ,if this be too low1 basic ceric sulphate separates on boiling1 and the estimation fails2 if it be too high1 oxidation to the ceric salt is hindered1 and may even be inhibited4 ,this difficulty disappears in the modified method of ,waegner and ,muller1#bcd in which the oxidation to the ceric condition is effected by means of bismuth tetroxide in nitric acid solution4 ,a similar method1 in which reduction to the cerous state is effected by a ferrous salt1 in place of hydrogen peroxide1 has been employed by ,metzger4#bce #bcc ,ber4 #aijj1 #cc1 #aibd4 #bcd ,ber4 #aijc1 #cf1 #bhb and #agcb4 #bce ,j4 ,amer4 ,chem4 ,soc4 #aiji1 #ca1 #ebc2 see also ,metzger and ,heideberger1 ibid4 #aiaj1 #cb1 #fdb4 ,many attempts have been made to estimate cerium compounds by means of permanganate1 which in alkaline solution oxidises cerous salts to the ceric condition1 but the autoxidation of cerous hydroxide in the air introduces errors1 unless suitable precautions are taken4 ,meyer and ,schweitzer#bcf show that if the solution of the cerous salt be added1 with constant shaking1 to a known volume of a standard permanganate solution1 in presence of excess of magnesia1 the liquid being kept warm1 this difficulty is overcome2 the results are usually a little high1 however1 probably by reason of the oxidising action of the cerium dioxide on the other oxides present4 #bcf ,zeitsch4 anorg4 ,chem4 #aijg1 #ed1 #ajd2 see also ,roberts1 ibid4 #aiaa1 #ga1 #cje4 ,good results have also been obtained by the use of potassium ferricyanide in alkaline solution1#bcg oxidation taking place according to the equation3 ,ce,o #b,k,fe7,,cn7 #b,,koh #b,k,fe7,,cn7 #b;,ce,o ,h,o ,the ceric hydroxide is filtered off1 and the ferrocyanide formed estimated by means of permanganate in acid solution4 #bcg ,browning and ,palmer1 ,zeitsch4 anorg4 ,chem4 #aijh1 #ei1 #ga4 ,,chapter ,,xii ,,cerium ,,group 7continued7 ,,lanthanum1 ,,praseodymium1 ,,neodymium1 ,,and ,,samarium ,in his examination of the ceria earths in #ahci1 ,mosander discovered a new constituent1 which he called ,lanthana2 the new oxide was removed in solution when the ignited mixture was extracted with dilute nitric acid1 which leaves cerium dioxide undissolved4 ,on examination1 the new oxide was found to be heterogeneous2 by fractional precipitation with ammonia1 and subsequent recrystallisation of the sulphates1 he obtained two oxides1 which he called respectively ,lanthana 71 to be hidden71 from the absence of colour and specific reactions1 and ,didymia1 71 twins7 from their similarity and the occurrence of the two together4 ,samaria was isolated by ,lecoq de ,boisbaudran1 in #ahgi1 from a specimen of didymia extracted from the mineral samarskite4 ,two years previously1 ,delafontaine had shown that the didymia separated from this mineral was not spectroscopically identical with the oxide obtained from other sources1 and in #ahgh had isolated an oxide which he called ,decipia2 this was shown later1 however1 to be a mixture of which samaria was one component4 ,the samaria obtained by de ,boisbaudran was by no means pure1 being associated with terbia earths2 several investigators claimed to have separated from it new oxides1 most of these being proved afterwards to have been more or less impure specimens of ,europia4 ,in #ahhe1 ,auer von ,welsbach#bch employed for the first time the method which has now become of paramount importance for the separation of the cerium group1 viz4 the fractional crystallisation of the double nitrates4 ,by this method he succeeded in resolving ,mosander's didymia into two new oxides1 for which he proposed the names ,praseodidymia 71 leek-green71 from the colour of the salts1 and ,neodidymia respectively2 the shorter names praseodymia and neodymia are1 however1 now generally adopted4 #bch ,monats4 #ahhe1 #f1 #dgg2 ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #ahhe1 #ib1 ,,ii1 #cag4 ,illustration3 ,,group ,a ,,mixed ,,double ,,nitrates4 #b,r7,,no71#c,mg7,,no71#bd;,h,o4 -------------------------------- ------------------------------ #a #b #c #d ,la1 ,pr ,pr1 ,nd ,crude ,nd ,mother-liquors4 ,compounds4 ,compounds4 ,compounds4 ,fractionate as ,fractionate as ,continue the ,sa1 ,eu1 ,gd1 etc4 ,r7,,no71#b,,nh,,no1 #b,r7,,no71 ,separation4 ,crystallise with #d;,h,o4 #c,mn7,,no71#bd;,h,o4 ,bismuth magnesium nitrate4 ------- ------------- ---------------------- ,terbium elements4 --- #e #f #g #h #i ,pure ,la ,pr with ,la4 ,impure ,pr ,pure ,nd ,pure ,sa ,compound4 ,compound4 ,compound4 ,compound4 ,refine by ,continue4 ,continue4 ,refine by ,sulphate ,sulphate crystallisa- crystallisa- tion4 tion4 ------------- ---- ,mixture of ,pr4 ,pr1 ,la4 ,refine by ,sulphate crystallisation4 ,,fig4 #h4--,,separation ,,of ,,the ,,cerium ,,elements ,,separation ,the modern methods for the separation of these elements are based almost entirely on the differences in solubility of the various double nitrates4#bci ,the mixed double sulphates separated by saturation of a solution of the chlorides with sodium sulphate1 which contain the cerium and most of the terbium elements1 are transformed into nitrates1 and the neutral solution boiled with potassium bromate1 in presence of powdered marble1 till all the cerium is precipitated as basic ceric nitrate4 ,from the filtered solution the other elements are thrown down as oxalates1 transformed into the magnesium double nitrates 7,a in ,fig4 #h71 and fractionated from nitric acid solution#bdj until a rough separation has been effected 7fractions #a1 #b1 #c1 and #d74 ,the separation1 which is somewhat long and tedious1 is followed by means of the absorption spectra1 and by the colour changes of the fractions4 ,fraction #a1 containing lanthanum and some praseodymium1 should be faint green to colourless2 fraction #b is colourless by the complementary action of the coloured salts of neodymium and praseodymium2 fraction #c1 which should contain the crude neodymium salt1 is amethyst2 and fraction #d1 the mother-liquor1 is yellow from the presence of the samarium compound4 #bci ,the following scheme is largely from ,james1 #8,the ,separation of the ,rare ,earths1' ,j4 ,amer4 ,chem4 ,soc4 #aiab1 #cd1 #geg4 #bdj ,see ,demaray1 ,compt4 rend4 #aijj1 #acj1 #ajai and #aahf2 also ,drossbach1 ,ber4 #aijb1 #ce1 #bhbf1 and ,muthmann and ,weiss1 ,annalen1 #aijd1 #cca1 #a4 ,fraction #a is now converted to the double ammonium nitrates1 which allow of a readier separation at this stage2 two fractions are obtained1 of which the less soluble1 fraction #e1 is the fairly pure lanthanum compound1 whilst the more soluble1 fraction #f1 contains the praseodymium with a little lanthanum4 ,the lanthanum ammonium nitrate1 fraction #e1 is converted into the anhydrous sulphate1 which is dissolved in ice-water2 when the solution is gradually warmed1 the enneahydrate1 ,la7,,so71#i;,h,o1 separates1 and may be obtained perfectly pure by recrystallisation4 ,it is of interest that the radioactive element actinium is chemically very similar to lanthanum1 and follows it closely through the process of separation4 ,the mixed praseodymium and neodymium magnesium nitrates which constitute fraction #b are transformed into the double manganese nitrates1 and the crystallisation from nitric acid continued4#bda ,the less soluble part1 fraction #g1 is fairly free from neodymium1 and the separation is continued with that of fraction #f1 until both lanthanum and neodymium have been completely removed4 ,the more soluble part1 fraction #h1 yields the pure neodymium compound1 as does also the crude neodymium magnesium nitrate which constitutes fraction #c1 if the crystallisation be continued4 #bda ,cf4 ,lacombe1 ,bull4 ,soc4 ,chim4 #aijd1 iii41 #ca1 #egj4 ,the mother-liquors1 fraction #d1 are treated with bismuth magnesium nitrate1#bdb which is intermediate in solubility between the analogous compounds of samarium and europium1 and the crystallisation continued4 ,the less soluble fraction contains the samarium compound1 in which bismuth is the only impurity2 this is easily removed by treatment with sulphuretted hydrogen4 ,the remaining fractions are used as a source of the terbium elements 7see p4 #ahf74 #bdb ,see ,urbain and ,lacombe1 ,compt4 rend4 #aijc1 #acg1 #gib2 ibid4 #aijd1 #ach1 #hd and #aacf4 ,the double carbonate method#bdc is very suitable for the preparation of pure lanthanum compounds after the removal of cerium4 ,the mixture of salts is added to a warm #ej solution of potassium carbonate1 and to the clear liquid1 water is added gradually1 with constant stirring4 ,the double carbonates of the most positive elements are the least soluble1 and are first thrown down1 so that the precipitate is rich in lanthanum2 it is collected and washed with a #be potassium carbonate solution1 and the process repeated4 ,a few repetitions suffice to separate lanthanum completely from the other members of the group4 ,the method may also be used for the purification of praseodymium salts4 #bdc ,meyer1 ,zeitsch4 anorg4 ,chem4 #aijd1 #da1 #id4 ,lanthanum1 ,la #acij ,as the most electropositive element of the rare earth group1 lanthanum is the most similar in its chemical properties to the metals of the alkaline earths4 ,the metal itself 7see p4 #aae7 oxidises even in dry air1 and in moist air rapidly becomes coated with a white layer of hydroxide2 it attacks water1 and burns vigorously when heated in the air4 ,an alloy with aluminium1 of the formula ,la,al1 has been prepared by ,muthmann and ,beck#bdd2 it forms lustrous white crystals1 very stable in the air and very resistant towards acids4 #bdd ,annalen1 #aijd1 #cca1 #df4 ,the hydroxide is of interest from the fact that1 if precipitated under suitable conditions1 it has the power of taking up solid iodine to form a deep blue adsorption compound#bde2 colloidal solutions of basic lanthanum acetate are also coloured blue by addition of a few drops of iodine solution4 ,if precipitation with alkali be carried out in presence of hydrogen peroxide1 an hydrated peroxide of the composition ,la,o1n,h,o is obtained4#bdf ,this compound partially decomposes with evolution of oxygen at ordinary temperatures2 towards carbon dioxide and acids it acts as a true peroxide1 with formation of hydrogen peroxide4 #bde ,damour1 ,compt4 rend4 #aheg1 #dc1 #igf2 see also ,biltz1 ,ber4 #aijd1 #cg1 #gai #bdf ,melikoff and ,pissarjewski1 ,zeitsch4 anorg4 ,chem4 #ahii1 #ba1 #gj4 ,the oxide is colourless1 and forms colourless salts with those acids in which the anion is not coloured4 ,the oxide is distinguished from the other rare earth oxides in that it turns moistened litmus paper blue2 it resembles lime1 in hissing when slaked1 absorbing carbon dioxide from the air1 and liberating ammonia from ammonium salts4 ,by fusion with alkali carbonates1 and by digestion with concentrated alkali hydroxides1 ,baskerville and ,catlett#bdg claim to have obtained lanthanates and metalanthanates1 but their work has not yet been confirmed4 #bdg ,j4 ,amer4 ,chem4 ,soc4 #aijd1 #bf1 #ge4 ,the sulphate1 ,la7,,so71#i;,h,o1 is the least soluble of all the rare earth sulphates4 ,the enneahydrate is the only form stable at ordinary temperatures1#bdh though under special conditions1 hydrates with #f and with #af molecules of water of crystallisation have been obtained4 ,it separates in needles belonging to the hexagonal system2 #ajj parts of water dissolve at #j1 #cja1 and at #ajj1 #jfi parts of the salt4 ,the acetylacetone compound melts at #ahe4 #bdh ,muthmann and ,rlig1 ,ber4 #ahih1 #ca1 #agah4 ,a large number of other lanthanum compounds have been prepared1 but these are so typical of the rare earth salts generally that no detailed treatment is required2 for a full account of them1 the reader is referred to ,abegg's classical handbook4 ,atomic ,weight4--,a large number of determinations of this constant have been made1 but the results even of recent investigations do not agree so closely as might be desired4 ,the value adopted by the ,international ,committee1 #acij1 is based on the work of ,brauner and ,pavliek1#bdi carried out in #aijb4 ,these authors give an account of all the determinations made up to that date1 with critical discussion of the methods employed and the possible sources of error4 ,the more important investigations have been based on the ratio ,la,o 3 ,la7,,so71 for the determination of which the most stringent precautions must be taken4 ,the synthetic method has generally been employed1 on account of the tenacity with which the oxide clings to traces of sulphuric anhydride4 ,in this method1 the total decomposition of the acid sulphate1 and the protection of the very hygroscopic sulphate1 ,la7,,so71 from atmospheric moisture1 constitute the chief difficulties4 ,by this method1 ,h4 ,c4 ,jones#bej in #aijb obtained a result 7#achgf7 considerably lower than the value found by ,brauner and ,pavliek 7loc4 cit47 ,a later research by ,brill1#bea who carried out a synthetic sulphate determination on a minute scale1 using a ,nernst microbalance1 gave the value #acie1 which1 whilst considerably higher than either of the other figures1 shows that ,brauner and ,pavliek's number can hardly be too high4 #bdi ,trans4 ,chem4 ,soc4 #aijb1 #ha1 #abdc4 #bej ,amer4 ,chem4 ,j4 #aijb1 #bh1 #bc4 #bea ,zeitsch4 anorg4 ,chem4 #aijf1 #dg1 #dfd4 ,detection4--,pure lanthanum compounds show no absorption in the visible region1 and the pure oxide gives no cathode luminescence4 ,the emission spectra show very characteristic lines in the violet and ultraviolet4 ,the chief lines are3 #cidibg #cihhfi #dbchee #dcccih #fbejad #fbfbeb #fciddf ,for arc spectra see ,exner and ,haschek2 ,eder and ,valenta4#beb #beb ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aiaj1 #aai1 ,i,ia1 #ci4 ,praseodymium1 ,pr #adjf ,this element occurs only in small quantities in the commoner rare earth minerals1 and its separation in the pure state is in consequence a matter of very great difficulty4 ,the salts and their solutions have a characteristic green colour4 ,the salts are derived from the sesquioxide1 ,pr,o1 but a dioxide1 ,pr,o1 and an intermediate oxide of uncertain composition are known4 ,the absorption spectrum has five absorption bands1 one of which coincides with a band in the absorption spectrum of neodymium2 this fact has been interpreted as an indication of the non-elementary nature of both metals4#bec ,difference in the absorption spectra have been put forward by several workers as indicating the complex nature of praseodymium1 but an exhaustive examination by ,stahl#bed in #aiji showed that there is no reason to doubt that the metal is really an element4 #bec ,auer von ,welsbach1 ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aijc1 #aab1 ,,iia1 ,july2 also ,urbain1 ,ann4 ,chim4 ,phys4 #aijj1 vii1 #ai1 #ahd4 #bed ,le ,radium1 #aiji1 #f1 #bae4 ,the metal is prepared by electrolysis of the fused chloride2 in order to attain the temperature required to fuse the element1 a very thin cathode is employed2 if too powerful a current be used1 the dioxide is formed4 ,the metal is purified by remelting it in crucibles of magnesia1 under a layer of anhydrous barium chloride4 ,it has a yellowish shade1 and is more stable in the air than lanthanum and cerium4 ,for physical properties1 see p4 #aae4 ,no alloys have been prepared4 ,the hydroxide is thrown down by alkalies as a gelatinous green precipitate2 in the presence of hydrogen peroxide1 an hydrated peroxide1 which closely resembles the corresponding lanthanum compound1 is thrown down4 ,the ,oxides4--,by ignition of salts of volatile acids1 ,auer von ,welsbach#bee obtained an oxide to which he assigned the formula ,pr,o4 ,more recent work#bef has shown that the composition of the oxide obtained depends upon the conditions under which the various salts are decomposed4 ,by fusing the nitrate in presence of potassium nitrate at #djj-dej;,c41 ,meyer obtained the dioxide1 ,pr,o2 at higher temperatures this decomposes1 giving the intermediate oxides4 ,the formation of the dioxide is greatly influenced by the presence of other oxides1#beg--;ceric oxide1 acting as an oxygen carrier1 favouring whilst the other oxides hinder4 ,the pure dioxide is a brownish-black powder1 which resembles manganese dioxide1 but is less stable4 ,it liberates halogens from the halogen acids1 and oxidises manganese salts to permanganates1 but does not completely oxidise ferrous or stannous salts1 losing instead a part of its oxygen in the gaseous form4 ,the dioxide cannot be obtained in the wet way4 #bee ,monats4 #ahhe1 #f1 #dgg4 #bef ,see1 e4g4 ,meyer1 ,zeitsch4 anorg4 ,chem4 #aijd1 #da1 #id4 #beg ,brauner1 ,monats4 #ahhb1 #c1 #a2 ,marc1 ,ber4 #aijb1 #ce1 #bcgj2 ,meyer and ,koss1 ibid4 #cdgj4 ,when heated in a stream of hydrogen1 the dioxide yields the sesquioxide1 ,pr,o1 as a greenish-yellow powder1which readily absorbs oxygen from the air1 becoming brown1 with formation of the intermediate oxide4 ,the chloride1 ,pr,cl1#g;,h,o1 forms large green prisms1 very readily soluble in water2 #ajj parts of the solvent at #ac take up #ccdb parts of the hydrated salt1 the solution having the specific gravity #afhg4 ,the anhydrous chloride is a pale green deliquescent powder1 which melts at a red heat to a clear green liquid2 ebullioscopic measurements show that in alcoholic solution it has the simple molecular formula ,pr,cl4 ,the ,bromate1 ,pr7,br,o71#i;,h,o1 has been obtained by ,james and ,langelier#beh by dissolving the oxide in aqueous bromic acid1 and also by double decomposition4 ,it forms greenish hexagonal prisms1 melting at #efe1 and is readily soluble2 #ajj parts of water dissolve #aij parts of this salt at #be4 ,at #ajj it loses five molecules of water1 forming the tetrahydrate ,pr7,br,o71#d;,h,o1 which loses all its water at #acj4 ,the anhydrous salt begins to decompose at #aej4 #beh ,j4 ,amer4 ,chem4 ,soc4 #aiji1 #ca1 #iac4 ,the sulphate crystallises with #h molecules of water of crystallisation at ordinary temperatures1 but hydrates with #ae1 #ab1 and #e molecules of water respectively have been described4 ,the octohydrate is considerably more soluble than lanthanum sulphate enneahydrate4 ,the anhydrous salt is a bright green powder4 ,praseodymium acetylacetone melts at #adf4 ,atomic ,weight4--,the value #adjf1 adopted by the ,international ,committee1 is based on the work of ,jones1 v4 ,scheele1 ,auer von ,welsbach1 and ,feit and ,przibylla2 the work of ,brauner1 however1 points consistently to a higher atomic weight4 ,most of these investigators have used the sulphate method4 ,the first determinations of von ,welsbach for the newly discovered element#bei gave the value #adjh 7see p4 #agi72 another series of determinations published in #aijcbfj gave the mean value #adjeg4 ,jones#bfa obtained the sesquioxide for the synthetic sulphate operation by reduction of the peroxide in a current of hydrogen2 according to ,brauner1 this method gives an oxide which is not perfectly pure1 probably by absorption of water vapour and carbon dioxide from the air4 ,jones' mean value was #adjdff4 v4 ,scheele#bfb used the same method1 as well as a combined oxalate-sulphate method2 his figures vary considerably1 the mean value being #adjee4 ,feit and ,przibylla1#bfc using their volumetric method1 obtained the value #adjed4 #bei ,monats4 #ahhe1 #f1 #dgg4 #bfj ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aijc1 #aab1 #ajcg4 #bfa ,amer4 ,chem4 ,j4 #ahih1 #bj1 #cde4 #bfb ,zeitsch4 anorg4 ,chem4 #ahih1 #ag1 #caj4 #bfc ,zeitsch4 anorg4 ,chem4 #aijf1 #ej1 #bdi4 ,brauner's earlier work1#bfd carried out in #ahih1 gave the value #adjie4 ,in #aija this author#bfe carried out an extensive research on the atomic weight of praseodymium1 employing four different methods with spectroscopically pure material2 the mean value of his very concordant results was #adjig1 almost the value he obtained in #aija4 ,a further investigation into the value of this constant appears desirable4 #bfd ,proc4 ,chem4 ,soc4 #ahih1 #ad1 #gj4 #bfe ,ibid4 #aija1 #ag1 #fe2 see also ,abegg1 ,,iii1 i4 #bfc4 ,detection4--,the maxima of the absorption bands are given by ,rech#bff as follows3 #bff ,zeitsch4 wiss4 ,photochem4 #aijf1 #c1 #daa4 ,yellow #eifd and #ehhb1 weak4 ,blue #dhac very intense4 #dfhc coincident with a neodymium band4 ,violet #dddb ,the arc spectrum is very rich in lines4#bfg ,the most intense1 which may be used also for identification1 are the following3 #bfg ,exner and ,haschek2 ,bertram1 ,zeitsch4 wiss4 ,photochem4 #aijf1 #c1 #af2 ,eder and ,valenta1 ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aiaj1 #aai1 ,,iia1 #fe4 #djjhij #dajjia #daahgj #dadccc #dagifj #dahigj #dbjfhh #dbbcah #dbbeej #dbdabj #dcjeii #ddbich #ddiffj #deajcb ,neodymium1 ,nd #addc4 ,neodymium is1 after cerium1 the commonest constituent of the cerium group in the more important rare earth minerals1 and its separation is therefore by no means so difficult as that of praseodymium4 ,the compounds of the element obtained by von ,welsbach in #ahhe were not pure1 being admixed with samarium compounds which had not been completely separated4 ,neodymium salts were first prepared free from samarium by ,demaray#bfh in #ahih2 they are of a violet-rose colour1 and show in solution a well-marked and characteristic absorption spectrum1 the bands being very numerous and sharply defined1 and extending over the whole optical region4 ,in chemical as well as in physical and crystallographic properties1 they show an extremely close resemblance to the compounds of praseodymium4 #bfh ,compt4 rend4 #ahih1 #abf1 #ajci4 ,on account of the high melting-point1 the preparation of the metal presents the same difficulties as that of praseodymium4 ,a current of #ij-ajj ampres is employed at a potential difference of #ae-bb volts2 this suffices to raise the thin carbon cathode to a bright white heat1 and to fuse the liberated metal4 ,for the properties of the element1 see p4 #aae4 ,the sesquioxide1 ,nd,o1 when perfectly pure1 has a light blue or lilac colour1 with a faint reddish fluorescence2 the shade varies somewhat according to the method of and temperature employed for the preparation4 ,a bluish or violet-red fluorescence is highly characteristic of the salts1 and is particularly noticeable if the powdered recrystallised oxalate be viewed in a good light4 ,the greyish or brownish colour of the oxide observed by some authors is probably due to traces of impurity4#bfi ,the existence of higher oxides of the formul ,nd,o and ,nd,o respectively1 which ,brauner#bgj put forward1 has been disputed by other writers1 though it is found#bga that in the presence of ceria and praseodymia1 the sesquioxide can take up more oxygen4 ,waegner#bgb claimed to have obtained the compound ,nd,o by heating the oxalate in a stream of oxygen1 though his material1 as well as that of ,brauner1 contained praseodymia4 ,more recently1 ,joye and ,garnier#bgc have shown that the spectrum attributed by ,waegner to the hypothetical ,nd,o was in reality that of an hydrated oxide1 #b,nd,o1#b;,h,o2 these authors have also prepared a second hydrated oxide of the formula #b,nd,o1#c;,h,o4 #bfi ,see ,waegner1 ,zeitsch4 anorg4 ,chem4 #aijd1 #db1 #aah2 also ,baxter and ,chapin1 ,j4 ,amer4 ,chem4 ,soc4 #aiaa1 #cc1 #a4 #bgj ,chem4 ,news1 #ahih1 #gg1 #afa2 ibid4 #aija1 #hc1 #aig4 #bga ,see ,meyer and ,koss1 ,ber4 #aijb1 #ce1 #cgdj2 and ,marc1 ibid4 #bcgj4 #bgb ,loc4 cit4 #bgc ,compt4 rend4 #aiab1 #aed1 #eaj4 ,the chloride1 ,nd,cl1#f;,h,o1 is obtained by crystallisation from aqueous solutions2 it is also precipitated by addition of water to an alcoholic solution4 ,it forms large deliquescent rose-coloured crystals2 #ajj parts of water at #ac dissolve #bdfb parts of the salt1 the saturated solution having the density #agda2 at #ajj1 #eaaf parts are dissolved4 ,the solution resembles those of the other chlorides of the group in that it readily dissolves the rare earth oxalates4 ,when heated in a current of hydrogen chloride of #acj1 the hexahydrate yields a monohydrate1 ,nd,cl1,h,o2 at #afj the anhydrous chloride is obtained as a very deliquescent rose-coloured powder1 which melts at a red heat to a clear red liquid4 ,the anhydrous chloride forms an additive compound ,nd,cl1#ab,,nh1 when exposed to the action of ammonia at low temperatures2#bgd by gradually heating this1 a large number of other additive compounds are formed1 containing smaller quantities of ammonia4 #bgd ,matignon and ,trannoy1 ,compt4 rend4 #aijf1 #adb1 #ajdb4 ,the anhydrous iodide1 ,nd,i1 has been obtained#bge by passing hydrogen iodide over the heated anhydrous chloride1 and also by heating the carbide in iodine vapour4 ,it fuses to a black liquid1 which at a higher temperature suddenly becomes transparent4 #bge ,matignon1 ibid4 #aije1 #adj1 #afcg4 ,the bromate1 ,nd7,br,o71#i;,h,o1 which is exactly similar to the analogous compound of praseodymium1 forms rose-coloured hexagonal prisms1 melting at #ffg4 ,the sulphate1 ,nd7,,so71#h;,h,o1 is isomorphous with the corresponding salt of praseodymium1 but is considerably less soluble4 ,only the one hydrate is known4 ,the nitrates show an interesting case of isomorphism with the corresponding bismuth nitrate hydrates4#bgf ,the stable form of the neodymium salt is the hexahydrate1 ,nd7,,no71#f;,h,o1 whilst the pentahydrate1 ,nd7,,no71#e;,h,o1 is labile4 ,of the bismuth salts1 on the other hand1 the pentahydrate is stable whilst the hexahydrate is labile2 but mixed crystals of both pairs may be obtained1 the stable neodymium hexahydrate with the unstable bismuth compound1 and the stable bismuth pentahydrate with the labile neodymium salt4 #bgf ,bodman1 ,ber4 #ahih1 #ca1 #abcg4 ,many double carbonates are obtained by dissolving the normal carbonate in excess of the precipitant4 ,the absorption spectra of these solutions1 which have a blue colour1 are abnormal and very intense1 and have been suggested as a basis of quantitative estimation4#bgg #bgg ,muthmann and ,stutzel1 ,ber4 #ahii1 #cb1 #bfec4 ,the acetylacetone derivative forms violet crystals1 melting at #add-ade4 ,a large number of organic salts of neodymium have been prepared by ,james1 ,hoben1 and ,robinson4#bgh #bgh ,j4 ,amer4 ,chem4 ,soc4 #aiab1 #cd1 #bgf4 ,atomic ,weight4--,the earlier determinations of this constant were carried out by the sulphate method1 the synthetic process being usually employed4 ,auer von ,welsbach1 at the time of the discovery of praseodymium and neodymium1#bgi gave the values #adcf and #adjh respectively for their atomic weights4 ,brauner1 who carried out a determination in #ahih1bhj showed that these numbers should be interchanged1 and gave the value #adcfc for neodymium4 ,boudouard1#bha employing the analytical sulphate method1 obtained the value #adcje1 whilst in the same year ,jones#bhb gave the value #adcf4 ,a second determination by ,brauner#bhc gave the value #adchi4 ,all these values are undoubtedly too low1 the material being probably contaminated with other earths4 #bgi ,loc4 cit4 #bhj ,proc4 ,chem4 ,soc4 #ahih1 #ad1 #gj4 #bha ,compt4 rend4 #ahih1 #abf1 #ijj4 #bhb ,amer4 ,chem4 ,j4 #ahih1 #bj1 #cde4 #bhc ,proc4 ,chem4 ,soc4 #aija1 #ag1 #ff4 ,in his second determination in #aijh1 ,auer von ,welsbach#bhd gave the value #added as the mean of three determinations4 ,feit and ,przibylla1#bhe using their volumetric method1 gave the value #addeb1 whilst ,holmberg1#bhf using material which he considered to have been the purest obtained up to that time1 obtained the figure #addaa4 ,more recently1 ,baxter and ,chapin#bhg have made determinations by treating the chloride with pure silver nitrate1 and weighing the precipitated silver chloride1 as well as by titration4 ,the mean value obtained by the first method--ratio ,nd,cl 3 #c;,ag,cl--was #addbgb 7extremes #addbej and #addbih71 and by the second method--ratio ,nd,cl 3 #c;,ag--was #addbfh 7extremes #addbdi and #addbhc71 giving the mean value for the whole series of #addbgj4 #bhd ,loc4 cit4 #bhe ,zeitsch4 anorg4 ,chem4 #aije1 #dc1 #bjb2 ibid4 #aijf1 #ej1 #bdi4 #bhf ,ibid4 #aijg1 #ec1 #abd4 #bhg ,proc4 ,amer4 ,acad4 #aiaa1 #df1 #bae4 ,the value adopted by the ,international ,committee is #addc4 ,detection4--,the absorption spectra of neodymium compounds have been examined by ,demaray1 ,forsling1 von ,welsbach1 ,rech1 ,schfers1 and ,baxter and ,chapin1 with concordant results4 ,the positions of the absorption maxima as given by ,holmberg#bhh from the measurements of ,forsling are as follows1 the weaker bands being omitted3 #bhh ,zeitsch4 anorg4 ,chem4 #aijg1 #ec1 #hc4 #fgge #fbag #eghe ,in concentrated solution #eged these give the #egce intense absorption #egaf region in the yellow4 #ecbc #ebaf ,in concentrated #ebjd solution these #eabd give one intense #ejhg band4 #dgde #dfhg #dfaj #dbga ,the arc spectrum is given by ,exner and ,haschek1 ,bertram1#bhi and ,eder and ,valenta4#bij ,the most intense lines are as follows3 #bhi ,zeitsch4 wiss4 ,photochem4 #aijf1 #c1 #af4 #bij ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aiaj1 #aai1 ,,iia1 #eed4 #chfceb #cieacb #djfabg #daefcj #dbdged #dbhbfg #dcjcgh #dcbehg #dcgeaa #dcheha #ddjjif #dddfea #ddeaga #ddfcji #dibjhd #eibcce #ecaiih #eeideh #efbjge #fcajfi #fcadfi #fchecb ,samarium1 ,sa #aejd ,the samarium of the earlier chemists 7see p4 #afh7 contained a large proportion of the terbium elements1 from which a fairly complete separation was first effected by ,demaray in #aijj4bia ,by the fractional crystallisation of the double magnesium nitrate in presence of bismuth magnesium nitrate1 ,urbain and ,lacombe#bib succeeded in preparing samarium compounds1 which were shown by spectroscopic examination#bic to be free from other earths4 ,the element is intermediate in electropositive character and in the solubility relations of its salts between neodymium and the terbium earths2 its salts are topaz-yellow in colour1 and in concentrated solutions show absorption in the blue and violet regions4 ,the oxide is almost white in colour1 with only a faint yellow tinge4 ,a systematic investigation of samarium compounds was carried out by ,cleve1#bid but his work was vitiated by the fact that his material was very impure4 ,more recently1 the pure salts have been examined by ,matignon and his pupils4 #bia ,compt4 rend4 #aijj1 #acj1 #aahe4 #bib ,ibid4 #aijd1 #ach1 #hd and #aaff4 #bic ,eberhard1 ,zeitsch4 anorg4 ,chem4 #aije1 #de1 #cgd4 #bid ,trans4 ,chem4 ,soc4 #ahhc1 #dc1 #cfb2 ,bull4 ,soc4 ,chim4 #ahhe1 ii41 #dc1 #ec2 ,chem4 ,news1 #ahhf1 #ec1 #cj1 #de1 #fg1 #hj1 #ia1 #ajj4 ,the melting-point of the metal lies between #acjj and #adjj;,c41 so that its preparation by the electrolytic method is a matter of great difficulty4 ,a mixture of the chloride with one-third of its weight of barium chloride is electrolysed by means of a current of #ajj ampres1 using a cathode of only #be mm4 thickness2 the metal so obtained is greyish white in colour1 and is the hardest of the cerium elements4 ,the chloride separates from aqueous solution as the hexahydrate1 ,sa,cl1,h,o1 in large tabular yellow crystals4 ,the anhydrous chloride is white1 but fuses to a chocolate-brown liquid2 it forms a large number of additive compounds with ammonia4 ,when heated in an atmosphere of dry hydrogen or ammonia1 air and moisture being carefully excluded1 it yields the subchloride1#bie ,sa,cl1 as a dark brown crystalline solid1 insoluble in alcohol and all organic solvents4 ,samarous chloride dissolves in water1 forming a deep brownish-red solution1 which rapidly becomes colourless1 with evolution of hydrogen1 and precipitation of the oxide and oxychloride4 ,samarous iodide1 ,sa,i1 may be obtained by a similar process1 and closely resembles the chloride4 #bie ,matignon and ,cazes1 ,compt4 rend4 #aijf1 #adb1 #hc4 ,the bromate1 ,sa7,br,o71#i;,h,o1 melts at #ge1 and closely resembles the corresponding compounds of the didymium metals4 ,the sulphate crystallises with #h1 and the nitrate with #f molecules of water4 ,the carbonate1 ,sa7,,co71#c;,h,o1 can be obtained only by passing carbon dioxide through an aqueous suspension of the hydroxide2 addition of alkali carbonate to a solution of a samarium salt precipitates hydrated double carbonates4 ,the acetylacetone compound melts at #adf-adg;,c4 ,many organic salts have been prepared by ,james1 ,hoben1 and ,robinson 7loc4 cit474 ,atomic ,weight4--,the earlier determinations of this constant were carried out with material not entirely free from europium4 ,demaray#bif carried out a synthetic sulphate operation with the material which he obtained free from europium in #aijj1 and found values between the limits #adgb and #adhj4 ,the ,international ,committee has adopted the value #aejd1 which is based on the work of ,urbain and ,lacombe#big in #aijd4 ,these authors made determinations of three series of ratios1 obtained by 7a7 conversion of sulphate octohydrate to anhydrous sulphate1 7b7 conversion of anhydrous sulphate to oxide1 and 7c7 conversion of sulphate octohydrate to oxide2 these gave the values #aejcad1 #aejecc1 and #aejdhd respectively1 from which the mean atomic weight is #aejdd4bih #bif ,loc4 cit4 #big ,compt4 rend4 #aijd1 #ach1 #aaff4 #bih ,these numbers are calculated by ,brauner 7,abegg's ,handbuch1 ,,iii4 i4 p4 #bhe7 on the basis ,o #af1 ,s #cbjf1 ,h #ajjgf1 and are somewhat higher than those given by ,urbain and ,lacombe1 who used the round numbers ,o #af1 ,s #cb1 and ,h #a4 ,detection4--,the absorption spectrum of samarium compounds is only visible in fairly concentrated solutions1 so that the element cannot usually be detected in a mixture by this means4 ,the position of the maxima of the strongest bands 7,demaray1 loc4 cit47 are3 #dgf #dfc #dag #djb ,these are all in the blue and violet regions2 the first and second are in the neighbourhood of neodymium and europium bands 7q4v471 and in concentrated solutions the bands would partially coincide4 ,since these are the two elements from which the separation is most difficult1 and are moreover the most constant in their occurrence with samarium1 the absorption spectrum is of very little use as a test4 ,the arc spectrum is very rich in lines1#bii of which the most intense are3 #cgcicj #daebch #dbjcah #dbbedh #dbbihc #dbcfhh #dbefed #dcaiab #dcbiba #dccdcb #dcdgie #dciajc #ddbjgb #ddbacb #ddbdee #ddcdjg #ddcdeb #ddebib #ddedhd #ddehgj #ddfgej #deaihj #debdjh #deddab #deffch #degghh #dfdbda #dfgdgi #bii ,exner and ,haschek2 ,eder and ,valenta2 ,rtten and ,mersch1 ,zeitsch4 wiss4 ,photochem4 #aije1 #c1 #aha4 ,,chapter ,,xiii ,,the ,,terbium ,,group ,in his examination of the yttria earths in #ahdb1 ,mosander described two new oxides isolated from the old yttria4 ,to one of these1 an orange-yellow earth which yielded colourless salts1 he gave the name ,erbia2 the second earth1 which was colourless and gave rose-coloured salts1 he called ,terbia4 ,bahr and ,bunsen examined the yttria oxides in #ahff1 and obtained only the latter earth1 which gave rose-coloured salts2 to this they applied ,mosander's name ,erbia1 and stated that the earth to which ,mosander had given that name had no existence4 ,delafontaine1 however1 confirmed ,mosander's work1 showing that the orange-yellow earth which yielded colourless salts 7,mosander's ,erbia7 had been fractionated out of their material by ,bahr and ,bunsen in the double sulphate separation of the cerium group2 to avoid further confusion1 however1 he proposed to give to this oxide 7,mosander's ,erbia7 the name ,terbia1 leaving for the colourless oxide1 which forms rose-coloured salts 7which ,mosander had called ,terbia7 the name ,erbia applied to it by ,bahr and ,bunsen4 ,this reversed nomenclature has been generally accepted4 ,delafontaine1#cjj continuing his work on the earths from samarskite 7see p4 #afh7 announced in #ahgh the discovery of a new oxide1 ,philippia1 intermediate between terbia and yttria2 but this was subsequently shown to be a mixture of yttria and terbia 7see p4 #acc74 ,in the same year1 ,lawrence ,smith#cja announced the discovery of another oxide1 ,mosandria1 from the samarskite earths2 this was afterwards shown by ,lecoq de ,boisbaudran to be a mixture of terbia with gadolinia4#cjb ,in #ahhj ,marignac#cjc announced the discovery of two more new oxides1 ,y and ,y from the same mineral2 ,y was afterwards found to be identical with samaria1 whilst ,y was subsequently separated from the old terbia earths by ,lecoq de ,boisbaudran1 who proposed1 with the assent of ,marignac1 the name ,gadolinium4#cjd ,the terbia left after removal of the erbia earths and gadolinia was believed by that author to be still a mixture1 a conclusion supported by the work of ,hofmann and ,kruss in #ahic4cje #cjj ,compt4 rend4 #ahgh1 #hg1 #eei4 #cja ,ibid4 #ahgh1 #hg1 #adf4 #cjb ,ibid4 #ahhf1 #ajb1 #fdg4 #cjc ,compt4 rend4 #ahhj1 #ij1 #hii4 #cjd ,loc4 cit4 #cje ,zeitsch4 anorg4 ,chem4 #ahic1 #d1 #bg4 ,in #ahhf ,demaray#cjf isolated from samaria a new oxide1 which he designated ,s4 ,from his work on this oxide in #ahib-ahic1 de ,boisbaudran#cjg concluded that samaria consisted of at least three oxides1 samaria proper1 and two new oxides ,z and ,z4 ,in #ahif1 ,demaray#cjh separated an earth 1 which showed the spark-spectrum of ,z and the reversal spectrum of ,z1 and finally in #aijacji he obtained the new oxide in a fairly pure condition1 and gave it the name ,europia4 #cjf ,compt4 rend4 #ahhf1 #ajb1 #aeea4 #cjg ,ibid4 #ahib1 #aad1 #ege2 ibid4 #ahic1 #aaf1 #faa and #fgd4 #cjh ,ibid4 #ahif1 #abb1 #gbh4 #cji ,ibid4 #aija1 #acb1 #adhd4 ,the complicated history of the terbium group has been entirely cleared up by the work of ,urbain and his co-workers during the early years of the present century1 and processes have been devised by which the separation of the three members of the group from one another1 and from the related elements of the erbium group on the one side1 and samarium on the other1 can be satisfactorily accomplished4 ,the chemistry of this group1 therefore1 may be regarded as satisfactorily settled1 though relatively little is known of the properties of the elements and their compounds4 ,in their general chemical relations1 elements of the terbium group occupy an intermediate position between the cerium group and the elements of the yttrium group in the narrower sense4 ,in the solubility relations of the double salts1 they are bounded on the one side by samarium and the less soluble cerium group1 on the other by dysprosium and holmium and the more soluble yttrium group4 ,they show only very slight differences in electropositive character1 and methods based on differences in basic strength of the oxides1 therefore1 are of very little use for separating them from one another4 ,fractional precipitation with ammonia separates them in the order terbium1 samarium1 gadolinium1 and europium--samaria being less strongly basic than the oxides of gadolinium and europium2 this constitutes an exception to the general rule regarding the solubilities of the double nitrates and sulphates with increasing electropositive character4#caj ,the difficulties of separation are greatly increased by the very small proportions in which the elements are usually found in rare earth minerals4 ,gadolinium usually occurs in the largest quantities2 in consequence of this1 there is little doubt that most of the material described by the earlier workers as terbia consisted very largely of gadolinia4 #caj ,see ,lecoq de ,boisbaudran1 ,compt4 rend4 #ahij1 #aaa1 #cid4 ,the group is not characterised by well-marked absorption spectra2 europium and terbium show weak absorption in the blue region4 ,terbium1 of which the salts are colourless1 forms a very strongly coloured peroxide1 analogous to that of praseodymium2 small quantities of this give to the mixed oxides obtained by ignition the characteristic yellow colour1 whilst mixtures richer in the peroxide become correspondingly darker and darker4 ,,separation ,in the double sulphate separation of the yttrium and cerium groups1 the terbium elements divide themselves between the soluble and the insoluble portions2 if the separation is made as complete as possible by addition of a large excess of alkali sulphate under suitable conditions1 the larger part of the compounds of the group will be precipitated with the cerium elements4 ,in the separation of the cerium elements the terbium elements collect in the most soluble fractions1 and the mother-liquors of the double nitrate crystallisations therefore form a very convenient source of these elements4 ,a considerable proportion1 however1 will usually remain in solution with the double sulphates of the yttrium group2 in the bromate separation of these 7see p4 #aih71 the terbium elements collect in the least soluble fractions4 ,by careful fractionation under suitable conditions1 the double sulphate method may be used to separate the terbium group completely from the cerium and yttrium elements4 ,a very convenient method of separating the terbium group from a rare earth mixture is the ethylsulphate process of ,urbain4 ,by fractional crystallisation of these salts from alcohol or water1 the separation into three groups can be satisfactorily accomplished4 ,for the separation of the terbium elements from one another1 the nitrate and double nitrate methods are most suitable4 ,samarium can readily be separated by crystallisation of the double magnesium nitrates in presence of bismuth magnesium nitrate2 by continuing the fractionation1 europium magnesium nitrate can be separated in a pure state1 as there is a considerable difference between the solubility of this salt and the corresponding compound of gadolinium2#caa the process1 however1 is somewhat long and tedious4 ,for the separation of gadolinium and terbium1 the double nitrates are converted into the simple nitrates1 and these fractionated from nitric acid in presence of bismuth nitrate4 ,the gadolinium nitrate separates before the bismuth nitrate1 and may be obtained fairly pure in this way1 though the process is extremely tedious1 and several thousand recrystallisations are required4#cab ,terbium nitrate has almost the same solubility as bismuth nitrate1 and the two separate together in the middle fractions4 ,the more soluble nitrates of the erbia earths collect in the mother-liquors4 #caa ,james 7,j4 ,amer4 ,chem4 ,soc4 #aiab1 #cd1 #geg7 employs at this stage the fractional crystallisation of the double nickel nitrates4 #cab ,see ,urbain1 ,compt4 rend4 #aijd1 #aci1 #gcf4 ,europium1 ,eu #aebj ,this element is one of the rarest of the whole group1 and occurs only in extremely small quantities4 ,monazite sand is said to contain about #jjjb per cent4 of the oxide1 though on account of the remarkable intensity of some of the stronger lines in the arc spectrum1 ,eberhard#cac was able to detect europium with ease in a mixture of rare earth oxides from that mineral1 after the separation of cerium4 ,the oxide has a pale rose colour2 the salts are also faintly coloured1 and in solution show weak absorption bands4 #cac ,zeitsch4 anorg4 ,chem4 #aije1 #de1 #cgh4 ,europium sulphate1 ,eu7,,so71#h;,h,o1 separates in pink crystals1 which are completely dehydrated at #cge2 europic chloride1 ,eu,cl1 in the anhydrous state forms fine yellow needles2 europium oxychloride1 ,eu,o,cl1 prepared by heating europic chloride in dry air to #fjj1 is a white solid1 insoluble in water1 but soluble in strong acids2 europous chloride1 ,eu,cl1 prepared by reduction of the higher chloride in hydrogen1 is a white amorphous solid1 soluble in water to a neutral solution1 which on boiling throws down the oxide1 ,eu,o4#cad ,several organic salts have been prepared by ,james and ,robinson4#cae #cad ,urbain and ,bourion1 ,compt4 rend4 #aiaa1 #aec1 #aaee4 #cae ,j4 ,amer4 ,chem4 ,soc4 #aiac1 #ce1 #ged4 ,atomic ,weight4--,using the material isolated from samaria1 ,demaray#caf in #aijj1 by the synthetic sulphate method1 found the atomic weight of europium to be about #aea4 ,urbain and ,lacombe#cag determined the value in #aijd1 with material free from gadolinium and samarium1 using the three ratios which they employed in the case of the latter element 7see p4 #ahb72 their values1 corrected by ,brauner1 were #aebjj1 #aeaic and #aeaid respectively4 ,another series of determinations was carried out by ,jantsch#cah in #aijh1 the same method being employed2 he obtained the mean value #aebjc1 with an error of #jb4 ,the ,international ,committee have adopted the value #aebj4 #caf ,compt4 rend4 #aijj1 #acj1 #adfi4 #cag ,ibid4 #aijd1 #ach1 #fbg4 #cah ,ibid4 #aijh1 #adf1 #dgc4 ,detection4--,the absorption spectrum was determined by ,demaray1#cai but is not sufficiently intense or characteristic for ordinary purposes of detection4 ,the spark spectrum has been investigated by the same author 7loc4 cit472 it is very bright1 and shows the three blue rays which characterised ,lecoq de ,boisbaudran's ,z4 ,the reversal spectrum shows the characteristic band of ,z4 ,the pure oxide1 according to ,urbain1#cbj shows no luminescence under the influence of cathode rays1 but when impure1 or very largely diluted with lime or gypsum1 it gives very bright and characteristic spectra4 #cai ,ibid4 #aijj1 #acj1 #dfi4 #cbj ,ibid41 #aijf1 #adb1 #bje1 #aeah4 ,the arc spectrum#cba is very characteristic1 and contains some exceedingly intense lines1 by means of which ,lunt#cbb has detected europium in the sun and in many stars4 ,the lines most suited for identification of the element are the following3 #cba ,exner and ,haschek2 ,eder and ,valenta1 ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aiaj1 #aai1 ,,iia1 #ca4 #cbb ,proc4 ,roy4 ,soc4 #aijg1 #gi2 ,a1 #aah4 #cfhheg #cgbeaj #chaihj #cijgbh #cicjff #cigbaf #dabiij #dbjebj #ddcege #debbgf #deidbg #dfbgdg #dffbaj #ffdedd ,gadolinium1 ,gd #aegc4 ,gadolinia is the commonest of the terbia oxides1 and occurs in considerable quantities in some of the rare earth minerals1 notably in samarskite and gadolinite2 its separation from the neighbouring oxides1 europia and terbia1 is1 however1 exceedingly difficult1 and has only been satisfactorily accomplished in recent times4 ,the gadolinium compounds prepared and examined by the earlier workers1 as appears from the atomic weight determinations1 must have been associated with earths of lower atomic weight1 and undoubtedly also with small quantities of terbium4 ,after the isolation of ,marignac's ,y1 and the examination of the element by ,lecoq de ,boisbaudran1 to whom the name gadolinium is due1 further investigations were carried out by ,bettendorff#cbc and by ,benedicts4#cbd ,pure gadolinia was probably first obtained by ,demaray1#cbe by fractional crystallisation of the magnesium double nitrate2 the oxide obtained by ,urbain and ,lacombe#cbf by crystallisation of the nitrates in presence of bismuth nitrate1 was proved to be spectroscopically pure by ,eberhard4#cbg #cbc ,annalen1 #ahib1 #bgj1 #cgf4 #cbd ,zeitsch4 anorg4 ,chem4 #aijj1 #bb1 #cic4 #cbe ,compt4 rend4 #aijj1 #aca1 #cdc2 ibid4 #aija1 #acb1 #adhd4 #cbf ,ibid4 #aije1 #adj1 #ehc1 etc4 #cbg ,zeitsch4 anorg4 ,chem4 #aije1 #ed1 #cgd4 ,the gadolinia obtained by ignition of the salts of volatile acids should be perfectly white2 presence of terbia causes it to assume a yellow colour4#cbh ,the salts are colourless1 and their solutions show no absorption in the visible region1 though ,urbain#cbi has shown that there are four strong bands in the ultraviolet4 #cbh ,eberhard 7loc4 cit47 has shown that even in the perfectly white oxide1 traces of terbia can be distinguished by spectroscopic examination4 #cbi ,compt4 rend4 #aije1 #adj1 #abcc4 ,the hydroxide1 ,gd7,,oh71 is a gelatinous precipitate with strongly basic properties1 rapidly absorbing carbon dioxide from the air4 ,the oxide1 ,gd,o1 also absorbs carbonic anhydride from the air1 and is easily soluble in acids1 even after strong ignition4 ,the element is therefore strongly electropositive4 ,its position among the yttrium elements1 however1 is justified by the properties of the platinocyanide1 #b;,gd7,,cn71#c,pt7,,cn71#ah;,h,o1 which forms long1 pointed red crystals1 with a green metallic lustre1 belonging to the rhombic system1 and isomorphous with the corresponding yttrium and erbium salts2 the cerium elements1 on the other hand1 give yellow platinocyanides1 with a blue metallic lustre1 which crystallise in the monoclinic system4 ,the nitrate1 ,gd7,,no71#f;,h,o1 separates from aqueous solutions at the ordinary temperatures in large crystals belonging to the anorthic system1 and is isomorphous with the corresponding compounds of praseodymium and neodymium4#ccj ,from solutions in strong nitric acid1 a pentahydrate is obtained1 which melts at #ib2 the hexahydrate melts at #ia4 ,the sulphate separates from aqueous solution as the octohydrate1 ,gd7,,so71#h;,h,o1 isomorphous with the corresponding salts of both groups4 ,the anhydrous sulphate is much less soluble in water at #j than the corresponding compounds of the cerium elements4 ,the selenate forms hydrates with #aj and #h molecules of water of crystallisation respectively2 these are isomorphous with the corresponding selenates of yttrium and the erbium metals4 #ccj ,lang and ,haitinger1 ,annalen1 #aijg1 #cea1 #dej4 ,atomic ,weight4--,the determinations of this constant made by the earlier workers were all carried out with impure material and gave results which were considerably too low4 ,the ,international ,committee have adopted the value #aegc1 which is based on the work of ,urbain4#cca ,in employing the analytical sulphate method1 that author observed that the anhydrous sulphate did not remain constant in weight when allowed to remain in a desiccator1 and that it could not be accurately weighed4 ,he therefore determined the ratio ,gd7,,so71#h;,h,o 3 ,gd,o1 by converting the octohydrate directly to oxide1 and obtained the mean value #aegbd4 #cca ,compt4 rend4 #aije1 #adj1 #ehc4 ,detection4--,pure gadolinium compounds show no absorption in the visible spectrum1 but there are four strong bands#ccb in the ultraviolet1 viz4 #caaf-caje2 #cjfj-cjeg2 #cjef-cjee2 and #cjed-cjej4 ,the arc spectrum#ccc is very rich in lines1 of which the most intense are the following3 #ccb ,urbain1 ibid4 #aije1 #adj1 #abcc4 #ccc ,exner and ,haschek2 ,eder and ,valenta1 ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aiaj1 #aai1 ,,iia1 #ba4 #cjhbae #cajjff #cdbbfb #cedeid #cedieb #ceheab #cfdfcf #cfgaci #cgaifc #cgdcfh #cgfhfj #cgiffb #chadah #chebfe #ciafgj #djcgdi #djejje #djfcfb #djgjea #djgcii #djhegc #djihhj #dacjei #dahddh #dbeaij #dbfbbd #dcbehc #dcbgbi #dcdbce #faadbf ,the spark spectra have been examined by ,demaray1#ccd ,baur and ,marc1#cce ,urbain#ccf and ,crookes4#ccg #ccd ,compt4 rend4 #aijj1 #aca1 #cdc4 #cce ,ber4 #aija1 #cd1 #bdfj4 #ccf ,loc4 cit4 #ccg ,proc4 ,roy4 ,soc4 #aije1 #gd1 #dbj4 ,terbium1 ,tb #aeib ,terbia occurs among the rare earth oxides in exceedingly small quantities1 and its separation has in consequence presented such great difficulties that only within the last few years have terbium compounds been completely freed from gadolinium and neighbouring elements4 ,in #ahhf ,lecoq de ,boisbaudran1#cch by fractional precipitation of the hydroxides with ammonia1 and subsequent fractional crystallisation of the double sulphates1 obtained an oxide much richer in terbia than any specimen previously prepared2 it was dark yellow in colour4 ,in #aijb ,marc#cci obtained from monazite a very dark oxide containing about #ae per cent4 of terbia1 whilst ,feit#cdj in #aije obtained a dark brown oxide consisting of gadolinia with about #ac per cent4 of terbia4 ,pure terbium compounds were obtained by ,urbain in #aijd1cda by fractional crystallisation of the nitrate from nitric acid1 in presence of bismuth nitrate1 and by crystallisation of the double nickel nitrates1 and precipitation with ammonia2 he showed that the element was identical with the ,z and ,z of de ,boisbaudran1#cdb with the of ,demaray1#cdc and with the ,g and possibly the ,g of ,crookes#cdd 7see p4 #aic74 #cch ,compt4 rend4 #ahhf1 #ajb1 #cie1 #dhc4 #cci ,ber4 #aijb1 #ce1 #bchb4 #cdj ,zeitsch4 anorg4 ,chem4 #aije1 #dc1 #bfg4 #cda ,compt4 rend4 #aijd1 #aci1 #gcf2 #aije1 #ada1 #eba2 #aiji1 #adi1 #cg4 #cdb ,ibid4 #ahie1 #aba1 #gji2 #aijd1 #aci1 #ajae4 #cdc ,ibid4 #aijj1 #aca1 #cdc4 #cdd ,trans4 ,chem4 ,soc4 #ahhi1 #ee1 #beh4 ,the element gives the white sesquioxide1 ,tb,o1 and colourless salts4#cde ,the peroxide1 of which the composition corresponds approximately to the formula ,tb,o1 is obtained as a brownish-black powder by ignition of suitable salts4 ,its presence1 even in small quantities1 gives so deep a colouration to the other earths that some kind of salt formation seems probable4 ,it is insoluble in cold acids2 it dissolves in hot nitric acid with evolution of oxygen1 forming a solution from which the nitrate1 ,tb7,,no71#f;,h,o1 melting at #hic1 separates on cooling4 ,in hot hydrochloric acid1 the peroxide dissolves with evolution of chlorine1 forming solutions from which the chloride1 ,tb,cl1#f;,h,o1 can be isolated with difficulty2 this salt is extremely deliquescent1 and easily forms supersaturated solutions4 ,the sulphate1 ,tb7,,so71#h;,h,o1 can be precipitated from a sulphuric acid solution of the oxide by addition of considerable quantities of alcohol2 it is isomorphous with the other sulphate octohydrates1 and is completely dehydrated at #cfj4 #cde ,the terbium compounds here described have been prepared by ,urbain 7loc4 cit47 from carefully purified material2 other compounds have been described by ,potratz 7,chem4 ,news1 #aije1 #ib1 #c71 but her material contained a large proportion of gadolinium4 ,atomic ,weight4--,the value adopted by the ,international ,committee is #aeib1 which was obtained by ,urbain in #aije 7loc4 cit47 from the ratio ,tb7,,so71#h;,h,o 3 ,tb7,,so74 ,this is the only determination on which reliance can be placed1 as the material of the earlier workers was seldom even approximately pure4 ,detection4--,solutions of terbium salts show only one band in the visible spectrum1 at #dhgg in the blue4 ,this band was observed by ,lecoq de ,boisbaudran in a specimen of terbia containing dysprosia1 and assumed by him to belong to a new element1 ,z 7loc4 cit47 ,in the ultraviolet nine absorption bands have been observed 7,urbain1 loc4 cit47 ,the spark spectrum shows the lines observed by ,demaray in #aijj1 and attributed by him to the new element 4 ,lecoq de ,boisbaudran's element ,z showed a green fluorescence with the reversed spark1 a phenomenon which ,urbain has found to be exhibited by pure terbium compounds4 ,the arc spectrum of ,urbain's pure terbia was examined by ,eberhard#cdf--see also ,exner and ,haschek1 and ,eder and ,valenta4#cdg ,the element may be detected in minerals and earth mixtures by the following lines3 #cebchb #cfgfeb #cgjcje #cgjdja #djjefb #dbghga ,the chief lines in the arc spectrum 7,exner and ,haschek7 are the following3 #ccbdec #cejicd #cecahf #cefaij #cefhfi #cfjjfj #cfbhec #cfejfj #cfeijb #cgjdaj #cgaaia #chdhij #chgdcc #chiicd #cibefj #cicige #ciggja #cihbjg #djjegj #djabii #dbghgj #dgebfi ,pure terbia does not exhibit the phenomenon of cathode luminescence1 but gadolinia containing a trace of terbia shows a marked green fluorescence1 which was attributed by ,crookes to a new ,meta-element1 ,g4 ,a trace of terbia in aluminium oxide causes the latter to exhibit a highly characteristic intense white luminescence4 #cdf ,sitzungsber4 knigl4 ,akad4 ,wiss4 ,berlin1 #aijf1 #ah1 #che4 #cdg ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aiaj1 #aai1 ,,iia1 #ad4 ,,chapter ,,xiv ,,the ,,erbium ,,and ,,ytterbium ,,groups--,,yttrium ,,and ,,scandium ,in his examination of the #8,yttria' of ,gadolin and ,ekeberg1 during the years #ahci to #ahdc1 ,mosander1 by methods based on differences in strength of the oxides as bases1 separated the earth into three new oxides1 yttria proper1 the most strongly basic1 terbia1 intermediate in strength1 and erbia1#cdh the least basic4 ,no further separation was effected until #ahgh1 when ,marignac1 by fractional decomposition of the nitrates1 separated from erbia a new oxide1 for which he proposed the name ,ytterbia2 the new oxide was the least basic of the erbia earths4 ,in the following year1 ,nilson#cdi isolated from ytterbia a still less basic oxide1 by the same method2 he proposed the name ,scandia1 to recall the fact that it occurred in gadolinite and euxenite1 which up to that time had been found only in ,scandinavia4 ,in #ahgi also1 ,soret#cej announced the discovery of a new element ,x1 evidence for the existence of which he had obtained during a spectroscopic examination of a mixture of erbia and terbia earths2 the oxide of ,x was isolated in the same year by ,cleve#cea from the old erbia1 by fractional decomposition of the nitrates1 and the name ,holmium1 from the town of ,stockholm1 was proposed for the new element4 ,the same investigation led to the discovery of ,thulium1 which derives its name from ,thule1 an old name for ,scandinavia4 #cdh ,the reversed nomenclature of ,delafontaine is here employed 7see p4 #ahd74 #cdi ,compt4 rend4 #ahgi1 #hh1 #fdb1 #fde4 #cej ,ibid4 #ahgi1 #hi1 #eba4 #cea ,ibid4 #ahgi1 #hi1 #dgh1 #gjh4 ,lecoq de ,boisbaudran#ceb in #ahhf showed ,cleve's ,holmia to be a mixture of at least two oxides2 he retained the name ,holmium for the element which gave the most characteristic absorption bands of the old holmium1 and proposed the name ,dysprosium 7from 1 difficult of access7 for the second element4 ,the name ,erbia was retained for the oxide remaining after the removal of holmia1 thulia1 and dysprosia from the old erbia2 the homogeneity of this erbia has been called in question1 but is now fairly firmly established4 ,the individuality of dysprosium#cec and holmium#ced may also be regarded as definitely established2 that of thulium remains doubtful 7see p4 #bjd74 #ceb ,ibid4 #ahhf1 #ajb1 #ajjc1 #ajje4 #cec ,urbain1 ,compt4 rend4 #aijf1 #adb1 #ghe4 #ced ,holmberg1 ,zeitsch4 anorg4 ,chem4 #aiaa1 #ga1 #bbf4 ,the homogeneity of ytterbia was questioned by ,auer von ,welsbach#cee in #aijf2 by fractionation of the ammonium double oxalates1 that author isolated the oxides of two new elements1 for which he proposed the names ,aldebaranium and ,cassiopeium4 ,by fractionation of the nitrates from nitric acid solution1 ,urbain#cef arrived at the same result1 and proposed the names ,ytterbium 7,neoytterbium7 and ,lutecium1 which have been adopted by the ,international ,committee4 ,the latter author1 employing the same method in the fractionation of the gadolinite earths1 has recently obtained very strong evidence of the existence in this group of another element1 for which he proposes the name ,celtium2#ceg the discovery1 however1 awaits confirmation4 #cee ,monats4 #aijf1 #bg1 #ice2 #aijh1 #bi1 #aba4 #cef ,compt4 rend4 #aijg1 #ade1 #gei4 #ceg ,ibid4 #aiaa1 #aeb1 #ada4 ,,separation ,in the separation of the yttrium elements1 methods based on differences in electropositive character are of much greater importance than in the separation of the cerium and terbium groups1 and the method of nitrate fusion has been very largely employed even in comparatively recent work4 ,this method1 which was introduced by ,berlin in #ahfj1 has been of great value in the separation of yttrium and the ytterbium elements from the erbium group2 it was employed in the isolation of ytterbium by ,marignac1 and of scandium by ,nilson4 ,if a concentrated solution of the nitrates be evaporated down1 and the syrupy residue subjected to gradually increasing temperature1 the nitrates of the ytterbium elements and scandium are converted first into the basic nitrates2 at somewhat higher temperatures the erbium salts are decomposed1 whilst yttrium nitrate and the nitrates of any cerium elements present are the last to break up4 ,if the mixture of basic and neutral nitrates be dissolved in boiling water1 the former1 being less soluble1 crystallise out on cooling1 and may be separated by this means1 the process being repeated with the filtrate containing the unchanged nitrates4 ,in this way1 the weakly basic scandia and ytterbia quickly collect in the first fractions1 whilst the oxides of the erbia group are easily separated from the more strongly basic yttria4 ,the presence of the intermediate terbium group renders the process much less easily workable4 ,the process may be modified by raising the temperature to such an extent that the soluble basic nitrates are converted into insoluble superbasic nitrates1 the temperatures at which this change occurs increasing from element to element as the positive character becomes more marked2 the mixture of basic and superbasic salts is then extracted with dilute nitric acid which leaves that latter undissolved and removes the more positive elements in solution4 ,fractional precipitation of the hydroxides by means of ammonia1 alkalies1 or alkaline earths has also been frequently employed4 ,a modification of this process is the precipitation with aniline1 carried out by ,kruss2#ceh in this method1 the solution of the chloride in warm dilute alcohol is treated with an alcoholic solution of the organic base4 ,another modification is the #8,oxide process' employed by ,auer von ,welsbach#cei for the separation of the cerium elements1 and by ,drossbach#cfj in the yttrium group4 ,the concentrated solution of the mixed salts is thoroughly digested with the oxides obtained by precipitating a fraction of the earths2 the more strongly basic oxides tend to displace the less basic1 so that these accumulate in the insoluble part4 ,the solution is filtered from the undissolved oxides1 another fraction precipitated1 and the oxides obtained from the precipitate digested with the concentrated solution as before4 #ceh ,zeitsch4 anorg4 ,chem4 #ahic1 #c1 #ajh1 #cec4 #cei ,monats4 #ahhc1 #d1 #fcj4 #cfj ,ber4 #aijb1 #ce1 #bhbf4 ,illustration3 ,,group ,b ,,yttrium ,,double ,,suplhates4 ,fractionate as ,bromates4 ---------------------------------------- ----------- ------------------------ #a #b #c #d #e ,gd1 ,tb1 ,dy4 ,tb1 ,dy1 ,ho1 ,dy1 ,ho1 ,er1 ,yt1 ,er1 and ,tm1 ,yb1 ,lu1 ,yt4 ,yt4 ,sc8 etc4 ,for separa- ,transform to ,fractionate ,fractionate ,continue4 tion of ,ethyl- by ,nitrate by ,nitrate ,terbium sulphates4 ,fusion4 ,fusion4 group4-- --- ,terbium ,group4 ---------- ---- ----------- --- ---------- ----- ----- ----- ----- #f #h #aj #ab #ad ,tb1 ,dy4 ,ho1 ,yt4 ,yt1 ,er4 ,tm4 ,lu4 ,continue ,fractionate ,continue4 ,bromate4 ,bromate4 ,ethylsulphate by ,nitrate ,fractiona- ,fusion4 ---- tion4 --- #g #i #aa #ac ,dy4 ,yt4 ,er4 ,yb4 ,ethylsulphate4 ,nitrate4 ,nitrate4 ,bromate4 --------- ---------- ,yb1 ,lu4 ,ct8 ,bromates4 ,bromate4 ,ho4 ,ho1 ,yt4 ,basic ,nitrate4 ,,fig4 #i4--,,separation ,,of ,,the ,,yttrium ,,elements ,the more modern methods of separation combine the above processes with the methods of fractional crystallisation1 for which the bromates and alkylsulphates of these elements are well adapted4 ,the procedure#cfa which experience shows will lead to a fairly rapid separation is roughly represented in ,fig #i4 ,the double sulphates 7,b71 left in solution after removal of the cerium and part of the terbium group1 are transformed into the bromates1 which are separated by fractional crystallisation into five main fractions4 ,the least soluble portion1 fraction #a1 contains the terbium elements with some dysprosium2 in the fractionation of the terbium group by means of the nitrates and double nitrates1 the dysprosium1 with some terbium1 collects in the final fractions 7fraction #f74 ,fraction #b contains terbium1 dysprosium1 holmium1 and yttrium as the bromates2 these are converted into the anhydrous chlorides1 from which1 by treatment with sodium ethylsulphate in alcoholic solution1 the ethylsulphates are obtained4 ,by fractional crystallisation1 dysprosium may be obtained in a fairly pure condition 7fraction #g71 the least soluble part 7fraction #f7 containing the terbium with some dysprosium4 ,holmium and yttrium collect in the most soluble part 7fraction #h71 from which pure holmium can be obtained by the method of nitrate fusion4 ,fraction #c contains yttrium and erbium1 with small quantities of dysprosium and holmium2 the latter are readily separated by the nitrate fusion1 which will also allow of a fairly complete separation of yttrium 7fraction #i74 ,fraction #d contains yttrium and erbium2 scandium if present will also collect here4 ,erbium can be obtained pure by the nitrate fusion2 the second fraction from this process contains both yttrium and erbium1 and may be further worked up with the fraction of similar composition 7fraction #aj7 from fraction #c4 #cfa ,james1 ,j4 ,amer4 ,chem4 ,soc4 #aiab1 #cd1 #geg4 ,the mother-liquors from the bromate separation 7fraction #e7 contain thulium and the ytterbium elements2 the crystallisation is continued1 and allows of complete separation of thulium and ytterbium1 and probably of lutecium1 though the most soluble fractions do not seem to have been fully separated4 ,,the ,,erbium ,,group ,the oxides of this group1 as contrasted with the ytterbia oxides1 give rise to coloured salts1 which in solution show definite absorption spectra in the optical region2 the spectrum of erbium salts is particularly definite and characteristic4 ,erbium has among the yttrium elements the place of neodymium among the cerium elements2 after yttria1 erbia is the commonest oxide of the yttria group1 though on account of the difficulties of separation the chemistry of erbium is by no means so complete and definite as that of neodymium4 ,the oxides in order of decreasing basicity1 as shown by the order in which they are thrown down by ammonia1 are3 dysprosia1 holmia1 erbia1 thulia2 the electropositive character becomes weaker1 therefore--as generally in the rare earth series--as the atomic weight of the elements increases4 ,dysprosium1 ,dy #afbe ,compounds of this element were probably prepared in the pure state for the first time by ,urbain#cfb in #aijf1 by the fractional crystallisation of the ethylsulphate4 ,he showed that after fourteen recrystallisations1 the absorption spectrum of the salts and the mean atomic weight of the element remain unaltered1 and that after removal of terbium by the very efficient ethylsulphate method1 all remaining traces of yttrium could be rapidly removed by crystallisation of the nitrate4 ,the salts have generally a more or less pronounced yellow colour4 #cfb ,compt4 rend4 #aijf1 #adb1 #ghe4 ,the oxide1 ,dy,o1 is a white powder which does not alter in composition when strongly heated in reducing or oxidising atmospheres4 ,it is remarkable in that it is the most strongly paramagnetic oxide known1 having a coefficient of susceptibility much greater than that of ferric oxide4#cfc ,the chloride crystallises with #f1 the sulphate with #h1 and the nitrate with #e molecules of water of crystallisation4 ,the bromate1 ,dy7,br,o71#i;,h,o1#cfd obtained by double decomposition1 melts at #gh4 ,the platinocyanide1 ,dy,pt7,,cn71#ba;,h,o1 forms bright red cubic crystals1 with greenish fluorescence4 #cfc ,compt4 rend4 #aijh1 #adf1 #ibb4 #cfd ,jantsch and ,ohl1 ,ber4 #aiaa1 #dd1 #abgd4 ,several other salts are described by ,urbain1 and by ,jantsch and ,ohl 7loc4 cit474 ,atomic ,weight4--,urbain and ,demenitroux#cfe determined this constant from the ratio ,dy7,,so71#h;,h,o 3 ,dy,o4 ,the mean value of six determinations carried out with material obtained by fractional crystallisation of the nitrate was #afbeb2 with material purified by the ethylsulphate crystallisation1 the mean of six determinations gave the value #afbed4 ,the ,international ,atomic ,weight is #afbe4 #cfe ,compt4 rend4 #aijf1 #adc1 #eih4 ,detection4--,lecoq de ,boisbaudran#cff and ,urbain#cfg give the position of the following absorption maxima in the visible and ultraviolet regions respectively3 #gec #cfhe #cch #dge #cgie #ccbe #deae #cfe #dbge #cea #cff ,ibid4 #ahhf1 #ajb1 #ajjc4 #cfg ,ibid4 #aijf1 #adb1 #ghe4 ,the arc spectrum of ,urbain's material was examined by ,eberhard1#cfh who gives as most suitable for detection of the element in a mineral or oxide mixture the following lines3 #ccheaf #cecahf #cecfag #cfdeed #chihfi #ciddhc #djjjei #djghaa #dahgjj #dbaahb #cfh ,publ4 astrophys4 ,observ4 ,potsdam1 #aiji1 #bj1 ,no4 #fj4 ,see also ,exner and ,haschek1 and ,eder and ,valenta4#cfi #cfi ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aiaj1 #aai1 ,,iia1 #i4 ,the ultraviolet arc spectrum and the cathode phosphorescence have also been examined by ,urbain4#cgj #cgj ,loc4 cit4 ,holmium1 ,ho #afce ,the individuality of this element can hardly be regarded as perfectly established1 though ,holmberg#cga has prepared salts which in solution show only faint indications of erbium and dysprosium1 when tested spectroscopically4 ,that author fractionated the yttrium elements obtained from euxenite by a long process of separation1 which involved crystallisation of the m-nitrobenzenesulphonates1 of the simple nitrates 7two series71 of the double ammonium oxalates1 and finally fractional precipitation of the hydroxides by ammonia4 #cga ,zeitsch4 anorg4 ,chem4 #aiaa1 #ga1 #bbf2 see also ,langlet1 ,abstr4 ,chem4 ,soc4 #aijg1 #ib1 ii4 #iee4 ,he determined the ,atomic ,weight as #afce1 which is the value accepted by the ,international ,committee1 and mapped the absorption spectrum4 ,the oxide1 ,ho,o1 is a pale yellow powder2 the salts are yellow1 with a faint orange tinge4 ,erbium1 ,er #afgg ,although erbia was separated by ,mosander seventy years ago1 it is doubtful if the perfectly pure oxide has ever been prepared4 ,whilst the individuality of the element is well established1 its homogeneity has frequently been called in question4 ,the name #8,neo-,erbia' was given by ,cleve#cgb to the residue left after the separation from the old erbia of ytterbia1 scandia1 thulia1 and holmia 7with which dysprosia 7q4v47 was also separated71 but the spectrum examination of ,kruss and ,nilson#cgc led them to regard ,cleve's oxide as still complex4 ,their results1 however1 were explained by the work of ,hofmann and his pupils1#cgd who consider erbia to be a homogeneous product2 the homogeneity of the element1 therefore1 may be considered as established1 though it would be strengthened by a more complete knowledge of the neighbouring elements1 holmium and thulium4 #cgb ,loc4 cit4 #cgc ,ber4 #ahhg1 #bj1 #bacd4 #cgd ,ber4 #aijh1 #da1 #cjh2 also ,hofmann1 ibid4 #aiaj1 #dc1 #bfca4 ,the element forms a rose-coloured oxide1 and rose-coloured salts1 which give to the compounds of the mixed erbia earths their characteristic colour4 ,the oxide gives a very definite and characteristic reflection spectrum1 but the salts do not possess this property2#cge the reflection spectrum remains unchanged in the presence of foreign oxides1 provided no combination occurs4 ,from the atomic weight determinations1 it seems clear that the salts described by ,cleve and his pupils#cgf were not pure erbium compounds2 a few salts only appear to have been recently obtained in the pure state for the atomic weight determination 7q4v474 #cge ,see ,kruss and ,bugge1 ,ber4 #aijh1 #da1 #cghc4 #cgf ,see ,compt4 rend4 #ahhj1 #ia1 #cha4 ,the sulphate separates from aqueous solutions at ordinary temperatures as the octohydrate1 ,er7,,so71#h;,h,o1 which forms rose-coloured monoclinic crystals isomorphous with the corresponding sulphates of the whole group4 ,the anhydrous sulphate is formed by long heating at #djj1 more quickly at #dge1 and can be heated to #fcj without decomposition4 ,at #hde a basic salt1 ,er,o1,,so1 is formed1 which begins to decompose at #iej2 at #ajee the transformation to the oxide is complete4 ,the ammonium and potassium double sulphates are easily soluble in cold water4 ,the oxalate is thrown down in rosettes of bright rosy plates1 which according to ,hofmann#cgg have the formula ,er7,c,o71#aj;,h,o1 even when dried in the air4 ,cleve believed the salt to be thrown down as the enneahydrate4 ,when kept in vacuo over phosphoric anhydride1 the decahydrate passes into the trihydrate1 which when heated decomposes1 passing into the oxide at a temperature of #ege4 ,the nitrate1 ,er7,,no71#e;,h,o1 separates from aqueous solution as the pentahydrate1 in large stable red crystals4 ,the platinocyanide1 ,er,pt7,,cn71#ba;,h,o1 has the characteristic red colour with green fluorescence4 ,the formate1 ,er7,,hcoo7--,cleve1 loc4 cit4--is a red powder1 obtained by dissolving the oxide in formic acid2 it crystallises from water as the dihydrate4 #cgg ,loc4 cit4 ,atomic ,weight4--,the determinations of the earlier workers1 being carried out with impure material1 gave results which differ very widely1 and are quite unreliable4 ,cleve's value of #ahhj1 for material free from ytterbia1 but not apparently free from earths of lower equivalent1 was #affbe2 ,brauner1#cgh using the same material in #aije1 obtained the much higher value #afgad4 ,the determinations of ,hofmann and ,burger#cgi in #aijh gave the mean value #afgch2 with purer material1 ,hofmann in #aiajchj obtained the mean value #afgfh1 on which is based the value accepted by the ,international ,committee1 #afgg4 #cgh ,abegg1 ,,iii4 i4 #cah4 #cgi ,loc4 cit4 #chj ,loc4 cit4 ,detection4--,salts of erbium give in solution absorption spectra which are well defined and highly characteristic1 though not so intense as those of praseodymium and neodymium4 ,hofmann and ,bugge#cha give the following absorption maxima for a #aj per cent4 solution of their pure nitrate in a layer of #ae mm4 thickness3 #ffg weak #fed strong #eda very weak #ebc very strong #eai shadowy #dib #dhg strong #dej #ddb weak #cha ,ber4 #aijh1 #da1 #cghc4 ,the arc spectrum has been mapped by ,eder and ,valenta#chb and ,exner and ,haschek4 ,the following lines are used by ,eberhard#chc for purposes of detection3 #cbcjgc #cbfdia #ccabef #ccgbib #cdiibh #cfibhe #chifdj #cijfdg #cichgi #chb ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aiaj1 #aai1 ,,iia1 #ah4 #chc ,publ4 astrophys4 ,observ4 ,potsdam1 #aiji1 #bj1 ,no4 #fj4 ,thulium1 ,tm #afhe ,the thulia isolated in #ahgi was described by ,cleve#chd as pale rose in colour2 in the following year1 having obtained it in larger quantity1 he found that it was white1 and dissolved in acids to form colourless solutions which showed absorption bands in the red and blue4 ,the spectra of the thulium compounds prepared by ,cleve were examined by ,thaln1#che who concluded that a new element was certainly present1 though it had not been freed from ytterbium and erbium4 ,incidental observations on the new oxide were made by various investigators1 but no extensive researches were carried out upon it until #aiaa1 when ,james#chf published an account of the separation and purification by the bromate method1 stating that after some #ae1jjj operations1 his products remained unaltered2 he gives1 however1 no spectroscopic determinations1 though part of his material1 spectroscopically examined by ,sir ,william ,crookes1 was described as #8,very good thulium1 with a trace of ytterbium4' ,in the same year ,auer von ,welsbach#chg published an account of a spectroscopic investigation1 as a result of which he concludes that thulium is a mixture of at least three elements1 of which the second1 ,tm ,,ii1 agrees fairly well in properties1 so far as the two accounts allow of comparison1 with the thulium of ,james4 #chd ,loc4 cit4 #che ,compt4 rend4 #ahhj1 #ia1 #cgf4 #chf ,j4 ,amer4 ,chem4 ,soc4 #aiaa1 #cc1 #accc4 #chg ,zeitsch4 anorg4 ,chem4 #aiaa1 #ga1 #dci4 ,thulia is described by ,james as a dense white powder1 with a greenish tinge1 which #8emits a carmine coloured glow1 when carefully made to incandesce4' ,the salts have a greenish tint1 very susceptible to traces of erbium2 addition of erbium compounds turn the solution first yellowish-green1 then colourless1 and finally pink4 von ,welsbach describes ,thulium ,,ii as forming an almost white sesquioxide1 which1 when heated in the flame1 gives a purplish light quickly succeeded by a splendid characteristic glow2 the salts are pale yellowish-green by daylight1 emerald-green by artificial light1 the colour being almost complementary to that of erbium salts4 ,in solution1 salts of ,tm ,,ii give the bands at #fhe and #dfd ascribed by ,james and other workers to thulium4 ,until further researches on these interesting results are published1 the elementary nature of thulium cannot be considered definitely settled2 it appears probable1 however1 that homogeneous salts of a definite element were obtained by ,james4 ,the following salts are described by ,james 7loc4 cit474 ,the chloride1 ,tm,cl1#g;,h,o1 separates at ordinary temperatures from the concentrated solution of the oxide in hydrochloric acid as greenish crystals1 very soluble in alcohol and water4 ,the bromate1 ,tm7,br,o71#i;,h,o1 forms pale bluish-green hexagonal prisms1 isomorphous with the analogous salts of the group4 ,the sulphate and nitrate separate as the octohydrates4 ,the precipitated oxalate has the formula ,tm7,c,o71#f;,h,o1 and is soluble in excess of alkali oxalate4 ,the acetylacetone derivative was prepared by dissolving the precipitated and well-washed hydroxide in alcoholic acetylacetone2 it recrystallises from absolute 787 alcohol as the dihydrate1 ,tm7,c,h,o71#b;,h,o4 ,the phenoxyacetate1 ,tm7,c,h,o,,ch,,coo71#f;,h,o1 was obtained in a similar manner by addition of the hydroxide to a solution of phenoxyacetic acid in dilute alcohol4 ,atomic ,weight4--,cleve gave the value #agjg for this constant1 but his material was very impure4 ,in a footnote to a paper published in #aijg1 ,urbain#chh pointed out that the value could not be above #afhe4 ,analyses of the salts prepared by ,james agree fairly well with the theoretical values calculated on this basis1 but a systematic determination with pure material has not yet been made4 ,the ,international ,committee 7#aiab7 have adopted the value #afhe4 #chh ,compt4 rend4 #aijg1 #ade1 #gfj4 ,detection4--,the element can be detected in solution by its absorption spectrum1 the most intense bands being in the neighbourhood of #fhe1 and #dfd4 ,for provisional arc spectra see ,exner and ,haschek1 and for spark spectra ,auer von ,welsbach 7loc4 cit47 and ,eder and ,valenta4#chi #chi ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aiaj1 #aai1 ,,iia1 #ajc4 ,ytterbium 7,neoytterbium1 ,aldebaranium71 ,yb #agbj4 ,lutecium 7,cassiopeium71 ,lu #agdj4 ,the first indication of the complexity of ,marignac's ,ytterbium was furnished on spectroscopic grounds by ,auer von ,welsbach in #aije2cij he showed that a separation could be effected by the fractional crystallisation of the ammonium double oxalates from concentrated ammonium oxalate4 ,three years later#cij he published a full account of his method1 gave atomic weight determinations1 and mapped the spectra of the two new elements4 ,in #aijg1 ,urbain#cia independently effected a separation by the fractional crystallisation of the nitrates from nitric acid1 and proposed the names ,lutecium 7from the old name for ,paris7 and ,neoytterbium for the elements4 #cij ,see ,monats4 #aijh1 #bi1 #bjd4 #cia ,compt4 rend4 #aijg1 #ade1 #gei4 ,the two new elements resemble one another so closely in chemical properties that the account given by ,astrid ,cleve in #aijbcib of the compounds of the old ytterbium applies in practically every detail to the new elements4 ,the oxides are white1 and yield colourless salts1 showing in solution no absorption bands in the visible region4 #cib ,zeitsch4 anorg4 ,chem4 #aijb1 #cb1 #abi4 ,the oxides1 ,r,o1 though perfectly white1 are coloured yellow or brown by the faintest traces of thulium4 ,they are attacked by acids only slowly in the cold1 but dissolve readily on warming2 lutecia is slightly the less strongly basic4 ,the chlorides crystallise with six molecules of water1 and are extremely soluble and deliquescent2 when heated in a stream of hydrogen chloride1 they form oxychlorides of the type ,r,o,cl4 ,the platinocyanides crystallise with #ah molecules of water1 and have the characteristic appearance of the analogous compounds of the yttrium elements4 ,the sulphates crystallise at all temperatures as the normal octohydrates1 and are moderately easily soluble in water2 conductivity measurements show that they are partially hydrolysed in solution4 ,the nitrates crystallise from concentrated aqueous or nitric acid solutions as the tetrahydrates2 by evaporation of the aqueous solutions over sulphuric acid1 the trihydrates are obtained4 ,these compounds are anomalous among the rare earth nitrates1 by reason of their low water content4 ,the neutral carbonates are thrown down by ammonium carbonate as the tetrahydrates2 if a stream of carbon dioxide be led into aqueous suspension of the hydroxides1 basic carbonates of the formula ,r7,,oh7,,co1,h,o1 are obtained4 ,the oxalates are precipitated as the decahydrates2 they are readily soluble in excess of alkali oxalate4 ,many other salts of the old ytterbium have been prepared4 ,atomic ,weights4--,the values determined by ,urbain 7loc4 cit47 for the fractions obtained by the nitrate method gave the number #agja for the least soluble fraction free from terbium1 and #agcd for the most soluble fraction4 ,auer von ,welsbach 7loc4 cit47 obtained the values #agbi and #agdb for the least soluble and most soluble fractions from the double oxalate crystallisation respectively4 ,more recently#cic he has determined these constants with highly purified material1 employing a modified method4 ,the weighed anhydrous sulphates are transformed into the oxalates1 which are then ignited to the oxides4 ,he obtained the values ,yb #agcjj1 ,lu #agejj4 #cic ,monats4 #aiac1 #cd1 #agac4 ,the values adopted by the ,international ,committee are ,yb #agbj and ,lu #agdj4 ,spectra4--,the spark spectra are of more use in distinguishing the two elements than the arc spectra4 ,the spark spectrum of the old ytterbium was mapped by ,exner and ,haschek1#cid and of the two compounds by both discoverers 7loc4 cit474 ,see also ,eder and ,valenta4#cie #cid ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #ahii1 #ajh1 ,,iia1 #aabc4 #cie ,ibid4 #aiaj1 #aai1 ,,iia1 #c4 ,the arc spectra have been mapped by ,eder and ,valenta 7loc4 cit47 and by ,exner and ,haschek2 the latter authors give as the most intense lines the following3 ,yb ,lu #cjcabf #bfaeej #ccigba #dabdhg #cajgii #biaaec #cdgbfe #dahddj #cbhiej #cjggge #cejgeg #deahgd #cdfddg #caihbg #cejhee #edgfhh #cihhaf #cbedde #ceedeh #eihcib #eeeffg #cbhahi #cefhjj #eihdcb #ccabcj #cfbdaj #fbbbaj #cceigd #cfcfda #fdfcdj #ccgffi #chgfhj ,celtium ,the separation of ,marignac's ytterbium into the two elements described above was accomplished by ,urbain with the yttria earths extracted from xenotime4 ,in carrying out the same process with the ytterbia earths from gadolinite1 that author#cif obtained from the mother-liquor an earth for which the coefficient of magnetisation was found to be #da #aj2 lutecia has a coefficient three to four times as great4 ,a spectroscopic examination revealed the presence of lines which did not correspond with those of any known body1 and ,urbain considered that a new element1 for which he proposed the name ,celtium1 with the symbol ,ct1 must be present4 ,lutecia from xenotime shows no trace of the new element4 #cif ,compt4 rend4 #aiaa1 #aeb1 #ada4 ,spectroscopic evidence for the existence of a third ytterbium element had previously been brought forward by ,auer von ,welsbach#cig and also by ,exner and ,haschek4#cih #cig ,monats4 #aijh1 #bi1 #bjd4 #cih ,exner and ,haschek1 ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aiaj1 #aai1 ,,iia1 #gga4 ,the new element appears to be intermediate between lutecium and scandium1 and therefore may be expected to have a higher atomic weight than the former element4 ,its chloride is more volatile than that of lutecium1 less volatile than that of scandium2 its hydroxide is more feebly basic than that of lutecium1 but more strongly basic than that of scandium4 ,urbain 7loc4 cit47 gives the following as the principal lines in the spectrum2 strong lines are denoted by a single1 very strong by a double1 asterisk3 #bdeid #bdfic #bdhaf 99 #becfi 99 #bfggg #bfheb 9999 #bgbia 99 #bgcgi #bgfeh 9999 #bhcdc 99 #bhcgc 99 #bhdeb 99 #bhgjb #bhhea 99 #bijci 99 #bicai #bidie 99 #cjhjg 9999 #caahf 9999 #cagad 99 #caigi 9999 #ccbfj 99 #cciae 99 #cffef ,yttrium1 ,yt #hij ,since the separation of yttria proper from the old yttria earths by ,mosander1 in #ahdb1 the individuality of yttrium has been well established4 ,the yttria of the workers of the sixties and seventies1 to judge from the atomic weight determinations1 must have been very impure1 but no doubts were raised as to its homogeneity4 ,by examination of the cathode luminescence spectra1 ,crookes#cii concluded that the oxide was of a complex nature2 ,lecoq de ,boisbaudran1 however1 showed that the phenomena observed by ,crookes were due to traces of impurity in his material1 a conclusion confirmed by the work of ,baur and ,marc4#djj #cii ,trans4 ,chem4 ,soc4 #ahhi1 #ee1 #bee4 #djj ,ber4 #aija1 #cd1 #bdfj4 ,the oxide is the most strongly basic of all the yttria earths2 in the basicity methods of separation1 therefore1 it collects in the end fractions1 and is easily separated from the erbia and ytterbia earths by the nitrate fusion and similar processes4 ,the terbia earths1 however1 which are comparable to it in basic strength1 cannot be easily separated by such methods2 processes of fractional crystallisation are very convenient in this case1 since yttrium falls1 with regard to the solubility of its simple salts1 among the erbium group--between holmium and erbium generally--which is easily separated from the less soluble terbium elements4 ,the separation of yttrium1 therefore1 affords an example of the combination of methods of both kinds4 ,the methods for the separation and purification of yttrium have recently been exhaustively examined by ,meyer and ,wuorinen4#dja ,they consider the chromate method suitable only if the terbium elements have already been removed4 ,the ethylsulphate method is said to be tedious1 whilst the ferrocyanide method indeed effects very rapid concentration1 but with great loss4 ,for purposes of concentration they find the most suitable method in the fractional hydrolysis of the phthalates2 these salts are soluble in cold water1 but hydrolyse when the solution is warmed1 the most positive elements remaining of course longest in solution4 ,for the final purification1 they recommend fractional precipitation of the iodate from nitric acid solution2 yttrium iodate being more soluble than the iodates of the erbium and ytterbium group1 the latter collect in the first precipitates4 #dja ,zeitsch4 anorg4 ,chem4 #aiac1 #hj1 #g2 ,meyer and ,weinheber1 ,ber4 #aiac1 #df1 #bfgb4 ,pure yttria is quite white1 and gives rise to colourless salts1 which in solution show no absorption spectrum in the visible region4 ,a very large number of yttrium compounds have been prepared1 of which sufficiently detailed accounts have been given in the general description of rare earth compounds4 ,for an exhaustive treatment1 the reader is referred to ,abegg's #8,handbuch4' ,the metal has probably not been obtained in the pure state2 impure yttrium has been obtained by ,winkler#djb by the action of magnesium on the oxide1 and by ,cleve#djc by the action of sodium on a mixture of the chloride with common salt1 and by electrolysis of the mixture of fused chlorides4 ,it is described as a greyish metal1 resembling iron in appearance2 it oxidises in the air and readily decomposes boiling water4 ,the hydroxide is thrown down as a gelatinous precipitate by alkalies2 ammonia throws down basic salts1 but in presence of hydrogen peroxide an hydrated peroxide is obtained4 ,the oxide absorbs carbon dioxide from the air1 and liberates ammonia from ammonium salts4 #djb ,ber4 #ahij1 #bc1 #ggb4 #djc ,bull4 ,soc4 ,chim4 #ahgd1 ii41 #ba1 #cdd2 ,cleve and ,hglund1 ibid4 #ahgc1 ii41 #ah1 #aic2 see also ,popp1 ,annalen1 #ahfd1 #aca1 #cei4 ,the anhydrous chloride has been prepared by many authors2 it melts at a relatively low temperature1 #fhj1 and is the most easily volatilised of all the rare earth chlorides4 ,after fusion1 it forms a mass of brilliant white lamell4#djd ,it is characterised by the ease with which it dissolves in pyridine4 ,from aqueous solution it separates as the hexahydrate1 ,yt,cl1#f;,h,o1 which melts at #afj4 ,the bromide separates from solution as the enneahydrate1 ,yt,br1#i;,h,o2 the bromate#dje also separates with #i molecules of water of crystallisation4 #djd ,compt4 rend4 #aijb1 #acd1 #acjh4 #dje ,james and ,langelier1 ,j4 ,amer4 ,chem4 ,soc4 #aiji1 #ca1 #iac4 ,the nitrate cannot be obtained anhydrous2 the normal hydrate1 ,yt7,,no71#f;,h,o1 loses #c molecules of water at #ajj1 but further heating converts it into basic salts4 ,a basic nitrate1 #c,yt,o1#d,n,o1#bj;,h,o1 is described by ,james and ,pratt#djf as stable at ordinary temperatures1 and in contact with solutions of the normal nitrate4 ,the sulphate octohydrate is isomorphous with analogous compounds of the rare earth elements1 and with the selenate1 ,yt7,se,o71#h;,h,o2 the latter compound can also form an enneahydrate4 ,the phosphate1 ,yt,p,o1 occurs in nature in the mineral xenotime1 and has been obtained in the laboratory in the crystalline form2 many other phosphates have been prepared4 ,the platinocyanide1 ,yt,pt7,,cn71#ba;,h,o1 has the characteristic red colour with greenish-blue fluorescence4 #djf ,j4 ,amer4 ,chem4 ,soc4 #aiaj1 #cb1 #hgc4 ,many organic yttrium salts have been prepared by ,james and ,pratt#djg and by ,tanatar and ,voljanski4#djh #djg ,j4 ,amer4 ,chem4 ,soc4 #aiaa1 #cc1 #accj4 #djh ,vide ,abstr4 ,chem4 ,soc4 #aiaj1 #ih1 i4 #hji4 ,atomic ,weight4--,the numbers obtained by the investigators who have determined this constant vary to such an extent that considerable uncertainty attaches to the value1 #hij1 at present accepted by the ,international ,committee4 ,the determinations carried out prior to #ahgj gave such diverse results that they are of little use in fixing the constant2 since that date1 all the investigations1 with the exception of the most recent1 have given values below #ij1 the sulphate method being generally employed4 ,cleve and ,hglund1#dji in #ahhc1 carried out six determinations by the synthetic method2 their results were concordant1 and gave the mean value #hieg4 ,brauner considers this result if anything too low1 as traces of undecomposed acid sulphate may have been present in the anhydrous sulphate4 ,the same method was employed again by ,cleve in #ahhd2daj the mean of twelve very concordant results gave the number #hiaa4 #dji ,loc4 cit4 #daj ,compt4 rend4 #ahhc1 #ie1 #abbe4 ,much stress is laid by ,brauner#daa on an unpublished determination of ,marignac1 carried out with material entirely free from terbia1 which gave the value #hhhh4 ,h4 ,c4 ,jones in #ahiedab carried out two series of determinations with material purified by ,rowland's method1 i4e4 precipitation with potassium ferrocyanide2#dac the results in both series were very concordant1 the synthetic method giving the value #hhie1 the analytical method the value #hhig4 ,this work has been taken by the ,international ,committee as the basis for the accepted value4 ,according to ,brauner1 the ferrocyanide method does not give perfectly pure material4#dad #daa ,abegg's ,handbuch1 ,,iii4 i4 #cbh4 #dab ,amer4 ,chem4 ,j4 #ahie1 #ag1 #aed4 #dac ,rowland1 ,chem4 ,news1 #ahid1 #gj1 #fh2 compare also ,crookes1 ibid4 #gj1 #ha-hb4 ,bettendorff 7see ,bhm1 ,die ,darstellung der seltenen ,erden1 ,i4 #dhj7 has also used the method4 #dad ,see also ,meyer and ,wuorinen 7loc4 cit474 ,egan and ,balke#dae have recently found the ratio ,yt,o 3 #b,yt,cl to be very suitable as a basis for atomic weight determinations2 the oxide is converted into the anhydrous chloride in a quartz flask4 ,in a preliminary experiment1 they obtain as a mean of three consistent determinations the provisional value #ijab2 the yttria employed was considered to contain not more than one-half per cent4 of erbia4 #dae ,j4 ,amer4 ,chem4 ,soc4 #aiac1 #ce1 #cfe4 ,recent work by ,meyer and his co-workers#daf indicates that the accepted value is too high4 ,preliminary work with the synthetic sulphate method gave the values 7corrected7 #hhga and #hhgc2 the mean value of six analytical sulphate determinations1 made on material carefully purified by the iodate method1 was #hhge1 the extreme values being #hhga and #hhgf4 ,they consider that the true atomic weight is #hhg1 the value of the second decimal figure being a little uncertain4 #daf ,meyer and ,wuorinen2 ,meyer and ,weinheber1 loc4 cit4 ,detection4--,the spark spectrum of yttrium has been examined by many authors1 and the ultraviolet as well as the visible regions have been mapped2 vide ,exner and ,haschek2 ,eder and ,valenta1 also ,becquerel4#dag #dag ,compt4 rend4 #aijh1 #adf1 #fhc4 ,the arc spectrum has been examined by ,kayser1 ,eberhard1#dah and ,eder and ,valenta2#dai ,exner and ,haschek give the following as the most intense lines3 #dah ,zeitsch4 wiss4 ,photochem4 #aiji1 #g1 #bde4 #dai ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aiaj1 #aai1 ,i,ia1 #a4 #cbafhc #cbdbdb #ccbhjb #cfjjib #cfaabj #cfbaaj #cfccbh #cffdgh #cgajdg #cggdeb #cghhhh #ciejeb #cihbgi #djgged #dajbeg #dabhej #dadcjc #dagggd #dcjbde #dcjigi #dcdhic #dcgeab #dhhchi #faiaia #fdcebg ,pure yttrium compounds should be colourless1 show no absorption in the visible region1 and yield a perfectly white oxide4 ,scandium1 ,sc #dda ,the scandia obtained by ,nilson in #ahgi was isolated from the minerals gadolinite and euxenite2 it consisted very largely of ytterbia1 as shown by spectrum examination#dbj and by atomic weight determinations1 which gave the value #ij4 ,in the same year#dba ,cleve prepared the oxide in a much purer state1 using as his source the minerals gadolinite and keilhauite2 he described several salts1 carried out atomic weight determinations by the analytical and synthetic sulphate methods1 and showed that scandium corresponds with the ,eka-boron of which the existence was predicted by ,mendelejeff in #ahga4dbb ,starting from a large quantity of euxenite1 ,nilson#dbc in the following year prepared several grams of approximately pure scandia1 which contained only traces of ytterbium4 #dbj ,thaln1 ,compt4 rend4 #ahgi1 #hh1 #fdb2 #ahhj1 #ia1 #de4 #dba ,compt4 rend4 #ahgi1 #hh1 #dai4 #dbb ,see also ,mendelejeff1 ,ber4 #ahha1 #ad1 #bhba4 #dbc ,ber4 #ahhj1 #ac1 #adci4 ,the investigation of scandium1 which occurs only in extremely small quantities in the minerals employed by ,nilson and ,cleve1 and was therefore believed to be exceedingly rare1 was not continued until #aijh1 when ,sir ,william ,crookes#dbd made a systematic investigation of a large number of minerals in order to find a convenient source of the element4 ,he showed that scandium is present in many rare earth minerals1 and selected as the most suitable for the extraction of the element a complex mineral named ,wiikite1 some specimens of which he found to contain over #a per cent4 of scandia 7see p4 #gj74 ,the mineral was decomposed by fusion with potassium hydrogen sulphate1 and scandia extracted from the rare earths by the nitrate fusion4 ,the separation effected on these lines was very thorough1 ,crookes considering a specimen of scandia unsatisfactory if it showed any trace of the dominant ytterbium line1 #cfidcdd1 on an over-exposed plate1 or if it gave an atomic weight for the element higher than #dda4 #dbd ,phil4 ,trans4 #aijh1 ,a1 #bji1 #ae4 ,a systematic investigation of the common rocks and minerals for scandium was carried out by ,eberhard in #aijh1 as a result of which processes for the extraction of the oxide from wolframite were worked out by ,r4 ,j4 ,meyer 7see pp4 #c1 #aca74 ,wolframite is a tungstate of iron and manganese1 containing1 in addition to other oxides1 small quantities of the rare earths1 of which considerable proportions are found to be scandia4 ,the mineral is fused with soda in the usual way1 and the rare earths concentrated by the oxalate method4 ,scandium is precipitated as the fluoride by addition of sodium silicofluoride to the boiling acid solution1 and purified by precipitation as the double ammonium tartrate4#dbe #dbe ,meyer and ,goldenberg1 ,chem4 ,news1 #aiab1 #ajf1 #ac4 ,whilst the researches of ,crookes and ,eberhard have shown how widely distributed the element really is1 the minerals which they found richest in scandium still contained extremely small quantities of the oxide4 ,the discovery of the mineral ,thortveitite 7see p4 #dd71 which contains about #cg per cent4 of scandia1 is therefore of the greatest scientific interest1 and will doubtless allow of a very searching examination of the properties of this interesting element4 ,whilst the low atomic weights of scandium and yttrium place them1 to some extent1 apart from the other rare earth elements1 the latter element at least is so closely allied in properties to the other members of the group that yttria is one of the typical oxides of the family4 ,scandium and its compounds1 however1 present many peculiarities of behaviour when compared with the typical members1 on the grounds of which ,urbain#dbf has contended that scandia should not be classed among the rare earths at all4 ,whilst this contention is perhaps rather extreme1 especially in view of the fact that in nature scandia always occurs with other yttria oxides1 it must be admitted that in many respects the element is anomalous4 ,the oxide is the weakest base of the whole group1 yet the oxalate is comparatively readily soluble in mineral acids 7compare p4 #acb71 and the potassium double sulphate is almost insoluble in potassium sulphate4 ,the sulphate is altogether exceptional in that it is very easily soluble in water1 and crystallises out with #f molecules of water of crystallisation4 ,the fluoride and the carbonate both dissolve readily in excess of precipitant1 whilst sodium thiosulphate precipitates a basic salt from neutral solutions4 #dbf ,chem4 ,news1 #aije1 #ij1 #cai4 ,meyer has pointed out the close resemblance between beryllium and scandium4 ,the oxide and salts are colourless2 the latter have a peculiar sweet astringent taste1 and readily yield basic salts4 ,the hydroxide1 ,sc7,,oh71 is thrown down by alkalies as a bulky white gelatinous mass2 the oxide is a white powder1 less readily soluble in dilute acids than most of the rare earths4 ,the fluoride is important on account of its insolubility in mineral acids1 which exceeds that of all the other rare earth fluorides1 and approaches that of thorium4 ,it is thrown down from neutral or acid solutions by addition of hydrofluoric acid or a soluble fluoride2 if the solution be boiled1 a soluble silicofluoride will also precipitate scandium fluoride1 though no precipitate is obtained in the cold4 ,this behaviour is due to the ease with which the silicofluoride is hydrolysed at high temperatures1 according to the equation3 ,sc7,si,f7 #f;,h,o #b,sc,f #c,si,o #f;,h,f and is of great value in separating scandium from the other earths4 ,the fluoride is extremely resistant to acids1 being completely decomposed only by fused bisulphate4 ,in the absence of acids1 the freshly precipitated fluoride dissolves in excess of concentrated alkali fluoride1 forming double salts2 in this behaviour1 scandium resembles zirconium1 but differs from thorium and the cerium and yttrium elements4 ,the chloride separates from solution at ordinary temperatures as the dodecahydrate1 ,sc,cl1#ab;,h,o1 which loses #i molecules of water when kept for six hours at #ajj4 ,the trihydrate ,sc,cl1#c;,h,o1 is converted into scandia at a red heat1 with the loss of #f molecules of hydrogen chloride4 ,the iodate1 ,sc7,,io71#ah;,h,o1 is obtained as an almost insoluble white crystalline powder by addition of ammonium iodate to a salt in solution2 hydrates with #ae1 #ac1 and #aj molecules of water are known1 and at #bej the anhydrous compound is obtained4 ,it resembles the iodates of the cerium and yttrium group in being soluble in strong nitric acid1 but the separation of thoria and scandia by this method is tedious and unsatisfactory4#dbg #dbg ,meyer1 ,winter and ,speter1 ,zeitsch4 anorg4 ,chem4 #aiaa1 #ga1 #fe4 ,the platinocyanide1 ,sc,pt7,,cn71#ba;,h,o1 was obtained by ,crookes#dbh by double decomposition of the sulphate with barium platinocyanide1 in crimson monoclinic prisms1 with a green fluorescence4 ,it dissolves in water to a colourless solution4 ,orlov#dbi shows that it can occur also in a second form1 stable at higher temperatures2 this is yellow1 with a blue fluorescence and crystallises with #ah molecules of water4 ,the two modifications resemble respectively the platinocyanides of the yttrium and of the cerium elements2 in this respect1 therefore1 scandium occupies an intermediate position between the two groups4 #dbh ,phil4 ,trans4 #aiaj1 ,a1 #baj1 #cei4 #dbi ,abstr4 ,chem4 ,soc4 #aiac1 #ajd1 i4 #bg4 ,the sulphate1 ,sc7,,so71 is obtained anhydrous by evaporating the excess of acid from a solution of the oxide in the concentrated acid1 care being taken to avoid too high a temperature4 ,the compound dissolves very easily in water1 and slowly hydrates itself with evolution of heat2 no crystals can be obtained from the solution until it has been concentrated to the consistency of a syrup1 when on cooling it slowly deposits the hexahydrate4 ,this effloresces in a dry atmosphere1 forming the pentahydrate1 which appears to be the most stable hydrate at ordinary temperatures4 ,according to ,nilson1 the hexahydrate loses #d molecules of water when maintained at #ajj4 ,at #bej it becomes anhydrous2 above that temperature1 basic salts are formed4 ,the potassium double sulphate1 #c,k,,so1,sc7,,so71 was shown by ,nilson to resemble the analogous cerium compounds in being insoluble in a saturated solution of potassium sulphate4 ,the nitrate1 ,sc7,,no71#d;,h,o1 separates from concentrated solutions over sulphuric acid as the tetrahydrate2 it is very soluble in water and alcohol1 and extremely deliquescent4 ,the carbonate1 ,sc7,,co71#ab;,h,o1 is thrown down by addition of ammonium carbonate as a bulky white precipitate1 easily soluble in a hot solution of the precipitant2 the solubility in excess may be used in the separation of scandia from yttria4 ,addition of water to such solutions causes separation of a basic carbonate1 but crystalline double carbonates may be obtained by evaporation of concentrated solutions containing a large excess of alkali carbonate4 ,the sodium compound1 ,sc7,,co71#d,na,,co1#f;,h,o1 is very sparingly soluble1 and has been used in the separation from thorium4 ,the oxalate1 ,sc7,c,o71#e;,h,o1 differs from other oxalates of the group1 which generally separate with #aj molecules of water of crystallisation1 not only in its water content1 and in its solubility in acids1 but also in the ease with which it forms double oxalates soluble in excess of alkali oxalate2 in this latter property it shows a further resemblance to zirconium and thorium4 ,the formate and acetate have the formul ,sc7,,oh77,,hcoo71,h,o and ,sc7,,oh77,,ch,,coo71#b;,h,o1 respectively4 ,a large number of organic salts have been described by ,sir ,william ,crookes4#dcj #dcj ,loc4 cit42 see also ,meyer1 ,zeitsch4 anorg4 ,chem4 #aijh1 #fj1 #acd2 ,meyer and ,winter1 ibid4 #aiaj1 #fg1 #cih4 ,atomic ,weight4--,the mean values obtained by ,cleve#dca in #ahgi were #ddif and #debj by the analytical and synthetic sulphate methods respectively4 ,in the following year ,nilson1#dcb using purer material1 obtained the value #ddac by the synthetic method4 ,meyer and others 7loc4 cit47 have criticised ,nilson's estimation on the ground of his empirical method of obtaining the neutral anhydrous sulphate4 ,determinations made with material purified from thorium by the iodic acid method gave the values #ddaa1 #ddaa1 #ddbj2 material purified by the double ammonium tartrate method gave the atomic weight #dcij4 ,meyer has shown that small quantities of thoria in the oxide cannot be detected spectroscopically2 the value of the magnetisation coefficient1 however1 showed the oxide obtained by the last method to be free from thoria1 and he considers another determination of the atomic weight to be necessary4 #dca ,loc4 cit4 #dcb ,loc4 cit4 ,the value accepted by the ,international ,committee is #dda4 ,detection4--,scandium gives no absorption spectrum in the visible region4 ,the spark spectrum has been examined by ,thaln 7loc4 cit47 and ,nilson2#dcc see also ,exner and ,haschek1 ,lockyer and ,baxendall1#dcd and ,crookes 7loc4 cit474 ,the arc spectrum has been examined by ,fowler1#dce ,eder and ,valenta1#dcf and ,exner and ,haschek4 #dcc ,compt4 rend4 #ahhj1 #ia1 #ef1 #aah4 #dcd ,proc4 ,roy4 ,soc4 #aije1 #gd1 #ech4 #dce ,phil4 ,trans4 #aijh1 ,a1 #bji1 #dg4 #dcf ,sitzungsber4 kaiserl4 ,akad4 ,wiss4 ,wien1 #aiaj1 #aai1 ,,iia1 #egf4 ,the most intense lines of the arc spectrum are the following3 #ccecij #ccgbcc #ceehfi #cefghi #cegbgc #cegfec #cfadjj #cfcjic #cfdbii #cijgfi #ciabjc #djbjfj #djbchh #dbdgjb #dcadca #dcbjih #dcbebb #dcgdfi #ddjjfc #ddaegh #fcjeid ,fowler 7loc4 cit47 examined the arc spectrum with reference to solar spectra4 ,for detection of the element in minerals see ,crookes 7loc4 cit47 and ,eberhard 7loc4 cit474 ,the purity of scandium preparations may be determined by the following tests3 7#a7 ,precipitation with thiosulphate in boiling solution should remove all the rare earth content from solution4 7#b7 ,the iodate test for thorium should give no result4 7#c7 ,the oxide must be perfectly white1 and salt solutions show no absorption4 7#d7 ,r4 ,j4 ,meyer has found that whilst #je per cent4 of thoria cannot be detected spectroscopically in scandia1 the magnetisation coefficient affords an exceedingly delicate test4 ,the value for pure scandia is -#jab #aj1 the oxide being diamagnetic2 for scandia with #je per cent4 thoria the coefficient was found to be #jjd #aj1 the mixture being paramagnetic4 ,,chapter ,,xv ,,the ,,group ,,iva ,,elements--,,titanium ,the oxides zirconia and thoria were generally classed among the rare earths by the earlier chemists4 ,this view was based partly upon the mode of occurrence of the oxides1 which are very generally associated in nature with rare earths1 and were believed to be equally sparingly distributed1 and partly on fallacious chemical analogies4 ,thus ,berzelius regarded thoria as a monoxide1 ,th,o1 and classed it with the other earth oxides1 magnesia1 lime1 ceria1 lanthana1 etc41 to all of which the general formula ,,ro was assigned4 ,zirconia was regarded as a sesquioxide1 ,zr,o1 analogous to alumina1 ,al,o1 which in turn showed many points of resemblance to the rare earths4 ,the introduction of the periodic classification1 and a wider knowledge of the chemical properties of the oxides1 have gradually altered the older conceptions1 and zirconia and thoria are now only classed under the head #8,rare ,earths' when that term is used in its widest sense4 ,more generally1 the term is restricted to the oxides of the cerium and yttrium elements1 which1 whilst they cannot all be placed in ,group ,,iii of the table1 yet constitute a series with properties which entitle them to be considered in that relation4 ,the elements which fall into group ,,iva of ,mendelejeff's classification are titanium1 zirconium1 cerium1 and thorium2 the elements of lower atomic weight1 carbon and silicon1 are placed by some authors in ,group ,,ivb1 by others in ,group ,,iva4 ,it is a feature of the periodic system that the members of the ,a and ,b families show great differences in the end groups1 ,i and ,,vii1 ,,ii and ,,vi1 which disappear as the middle groups are approached2 in group ,,iv the families ,a and ,b show only slight differences in properties1 corresponding to their amphoteric character and electrochemical indifference1 so that the elements carbon and silicon may be placed as well in the one as in the other4 ,generally they are placed in family ,b4 ,in its tetravalent condition1 titanium shows a close relationship to silicon2 the similarity is manifested by the ease with which the dioxide replaces silica in many minerals1 and the isomorphism of many titanates with corresponding silicates4 ,yet the strengthening of electropositive character1 which always accompanies the change in atomic weight in descending a vertical column of the table1 is very apparent in the case of titanium1 and its ability to form salts in the tetravalent state is a very important property4 ,this strengthening of the electropositive character is still more marked in the case of the succeeding elements4 ,the salts of zirconium are highly hydrolysed in solution1 but they are considerably more stable than those of tetravalent titanium2 the ceric salts show the same change1 whilst thorium salts are comparatively stable in solution1 and can be recrystallised from water without change4 ,zirconium hydroxide will not dissolve in alkalies1 though zirconates may be obtained in the dry way2 thorium hydroxide shows no acidic properties whatever4 ,the change in electrochemical character is accompanied by corresponding changes in physical properties of the elements and their compounds4 ,with the exception of cerium1 which has a very low melting-point 7#fbc71 the elements fuse only at high temperatures2 titanium is the most refractory1 zirconium melts at over #aejj1 and thorium at about #adej4 ,the boiling-points of the chlorides rise as the series is descended2 titanium tetrachloride boils at #acf1 zirconium and thorium chlorides at #djj-dej and #iej respectively2 zirconium chloride partly sublimes1 whilst ceric chloride decomposes when heated4 ,the elements of ,group ,,iva are distinguished from the rare earth elements by their much less strongly marked electropositive character4 ,this is apparent not only in the amphoteric nature of the oxides1 and in the ease with which the salts are hydrolysed in solution1 but in the more pronounced tendency to the formation of complex salts4 ,the complex fluorides of the type ,k,,rf are peculiarly characteristic1 and in the case of titanium and zirconium have been very important for purposes of analysis and atomic weight determination4 ,the solubility of zirconium and thorium salts in excess of alkali oxalate or carbonate is also in harmony with the less pronounced electropositive character of these elements4 ,the sulphates of titanium and zirconium appear to be of complex constitution1 whilst their neutral chlorides cannot be obtained from solution4 ,as is to be expected from its high atomic weight1 thorium approaches most nearly to the rare earths in chemical properties2 thus it forms stable double nitrates of the type ,r,th7,,no7 and its salts1 especially the sulphate1 resemble those of the rare earth elements in their solubility relations4 ,the elements titanium1 zirconium1 and thorium are distinguished also by the fact that they form no definite hydroxides4 ,the precipitates thrown down from solutions of the salts1 on addition of alkali1 are hydrated oxides1 which lose water continuously when dried1 giving rise to no definite chemical individuals until constant weight is reached with the anhydrous oxides4 ,the hydroxides have the further characteristic1 common also to the other members of ,group ,,iv1 of readily forming colloidal solutions and gels1 a property possessed to some extent also by the elements themselves1 and particularly by zirconium1 which1 when reduced from its compounds1 shows a great tendency to go into colloidal solution merely on washing4 ,highly characteristic also is the property of forming #8meta'-oxides 7acids7 and #8meta'-salts1 which is common to all the ,group ,,iv elements which have solid oxides4 ,in presence of hydrogen peroxide1 alkalies throw down characteristic hydrated peroxides1 which have definite acidic properties in the case of titanium3 the zirconium compound is less strongly acidic1 the cerium compound shows no tendency to salt formation1 whilst if hydrogen peroxide be added to a neutral or faintly acid solution of a thorium salt1 the precipitate is a peroxy-salt1 containing some acid grouping1 e4g4 ,,so1,,no4 ,with regard to valency1 the elements in the typical compounds are tetravalent4 ,titanium forms three series of salts1 in which the element is respectively di-1 tri-1 and tetravalent2 salts of the first two series have powerful reducing properties1 and the compounds in which the metal is tetravalent are most stable4 ,zirconium is always1 with the doubtful exception of its peroxy-compounds and the lower oxides1 tetravalent4 ,cerium1 as already described1 can form two series of compounds1 in which it is respectively tri- and tetravalent2 thorium1 like zirconium1 is always tetravalent4 ,titanium1 ,ti #dha ,though generally classed among the rare elements1 titanium is probably at least as widely distributed in nature as most of the common metals4 ,it occurs as the dioxide in small quantities in all the common silicate rocks and minerals1 and in traces in the animal and vegetable kingdoms2 the element has been identified in the sun and in many stars1 and has been found in meteorites4 ,probably the commonest mineral in which the element occurs in quantity is ilmenite1 or titaniferous ironstone1 which occurs in enormous quantities in many parts of the world 7see p4 #eg74 ,the pure dioxide occurs in the three forms ,rutile1 ,brookite1 and ,anatase 7q4v471 in which it is said to be isotrimorphous with tin dioxide4 ,other important titanium minerals are ,perovskite1 ,titanite or ,sphene1 the ,euxenite series1 and other minerals of the tantalo-columbate group 7see ,part ,i74 ,the commercial sources of titanium compounds are the minerals rutile and ilmenite4 ,these may be opened up by fusion with alkali or alkali carbonate2 the residue after extraction with water is dissolved in acid1 and precipitated with ammonia2 the mixture of iron and titanium oxides thrown down may be separated by one of the methods outlined on p4 #cci4 ,fusion with potassium bisulphate has also been employed4 ,a very satisfactory method is that of ,sthler1#dcg in which the ore is fused with carbon in the electric furnace4 ,the carbides so obtained are heated in a stream of chlorine1 when the volatile titanium tetrachloride distils over1 and may be obtained quite pure by redistillation2 by appropriate methods1 the required compounds may be obtained from this4 7,see also pp4 #cbf-g47 #dcg ,ber4 #aijd1 #cg1 #ddje2 #aijf1 #ch1 #bfai4 ,the ,metal4--,the difficulty of isolating metallic titanium in the pure state is very great1 on account of its great affinity for nitrogen1 oxygen1 hydrogen1 carbon1 etc41 the ease with which it forms alloys with all the common metals1 and the extremely high melting-point2 in consequence1 it is only within recent times that the element has been obtained in a state approximately approaching purity1 and the accounts given of its physical properties vary very widely4 ,berzelius prepared an impure titanium 7,ti #hf per cent47 by reduction of potassium titanofluoride with potassium2 the method was modified by ,whler1 who heated a tube containing two boats1 of which one was filled with the fluoride1 the other with sodium1 reduction being effected by the sodium vapour4 ,many authors have attempted the reduction of titanium tetrachloride by means of hydrogen4 ,by heating the tetrachloride with sodium in a cast iron bomb1 ,nilson and ,pettersson obtained a product containing #ie per cent4 of the element4 ,reduction of the dioxide by means of sodium1 magnesium1 silicon1 or aluminium has not been found to yield good results1 by reason of the ease with which titanium alloys with these elements4 ,reduction of the dioxide with carbon yields good results only when precautions are taken to avoid the formation of the compound which the element so readily forms with carbon and nitrogen4 ,moissan#dch found that if temperatures high enough to decompose this compound were used1 the product contained as the only impurity carbon1 which could be partly removed by fusing with the dioxide2 the product then contained #ih per cent4 of titanium4 #dch ,compt4 rend4 #ahie1 #abj1 #bij4 ,the element has been obtained in the fused condition by ,weiss and ,kayser1#dci who pressed the amorphous form into sticks1 under a pressure of #gj1jjj atmospheres1 and employed these as pencils for the electric arc in vacuo2 the metal fused1 forming globules on the ends of the electrodes1 which were detached after the apparatus had been allowed to cool4 #dci ,zeitsch4 anorg4 ,chem4 #aiaj1 #fe1 #chh4 ,the amorphous element is a dark powder1 resembling finely divided iron 7,ferrum reductum71 of density #ce-cf4 ,the specific heat rises rapidly with the temperature1 so that the atomic heat has the values #edj between #j and #ajj1 #fah between #j and #baj1 #gac between #j and #cjj1 and #ggg between #j and #ddj4 ,the amorphous element is said to be paramagnetic4 ,the fused carbonaceous product of ,moissan formed an extremely brittle mass1 with a shining white lustre on the fractured surface1 sufficiently hard to scratch quartz and steel2 its density was determined as #dhg4 ,the product of ,weiss and ,kayser was also extremely hard and brittle2 when rubbed against steel1 it gave bright sparks4 ,its density was found to be #eagd1 and the heat of combustion for the gram-atom1 #iggi ,k4 ,the amorphous variety is fairly stable in air1 but burns vigorously when heated in air1 oxygen1 or halogens4 ,heated in nitrogen or ammonia1 it reacts vigorously1 forming the nitride ,ti,n2 if carbon is present1 a peculiar substance of uncertain composition1 known as titanium cyanonitride1 is formed4 ,this substance is also obtained when air is passed over a heated mixture of the dioxide with coke1 and is found in blast-furnaces in which ores containing small quantities of titanium are worked2 it forms brilliant red cubes1 which are extremely hard and resistant to acids4 ,this substance1 as well as the nitride itself1 yields ammonia when heated in steam1 and has been proposed as a medium for #8fixing' atmospheric nitrogen 7see p4 #ccg74 ,the amorphous element also absorbs hydrogen1 when heated in the gas1 but no definite hydride is known4 ,it combines when heated with almost all the known non-metals1 and forms alloys with all the common metals4 ,moissan#ddj claims to have prepared a compound as hard as diamond by heating titanium with boron in the electric furnace4 ,the element attacks steam at a red heat4 #ddj ,loc4 cit4 ,the element is fairly resistant to acids in the cold1 but is readily attacked1 with evolution of hydrogen1 on warming4 ,hot dilute hydrochloric acid gives the trichloride2 but dilute sulphuric acid is variously reported to give the di- and tri-salt4 ,hot nitric acid oxidises it readily1 forming the so-called metatitanic acid4 ,hydrofluoric acid attacks it very readily1 forming the tetrafluoride4 ,,compounds ,,of ,,divalent ,,titanium4 ,the compounds of divalent titanium show resemblances to those of divalent iron1 chromium and vanadium1 but on account of the great difficulty of preparing them and protecting them from oxidation1 little is known of their properties and behaviour2 even the colour of the salts in solution is not known with certainty4 ,in its divalent state2 the element does not appear to act as a strongly positive metal2 the salts in solution are said to show an acid reaction1 whilst the precipitates thrown down with alkali oxalates and acetates are soluble in excess of the precipitant1 forming deeply coloured solutions4 ,with sodium phosphate the soluble salts give a bluish-black precipitate1 with potassium ferrocyanide and ferricyanide1 dark brown and reddish-brown precipitates respectively4 ,they are distinguished from salts of the higher oxides of titanium by the brown colouration produced by potassium thiocyanate in presence of hydrochloric acid4#dda #dda v4 d4 ,pfordten1 ,annalen1 #ahhf1 #bcd1 #beg2 #ahhg1 #bcg1 #bja2 see also ,ber4 #ahhi1 #bb1 #adhe4 ,the hydroxide is thrown down from solutions by addition of alkali1 alkali carbonate1 alkali cyanide1 or ammonium sulphide1 as a black precipitate4 ,it cannot be transformed to the corresponding oxide by drying1 since it attacks the water with evolution of hydrogen1 forming the dioxide4 ,the monoxide1 ,ti,o1 has probably never been obtained in the pure state2 it is formed by reduction of the dioxide with zinc or magnesium4 ,moissan#ddb obtained it in the form of black prismatic crystals by treating the dioxide with the calculated amount of charcoal in the electric furnace4 ,the sulphide1 ,ti,s1 is an extremely stable compound2 it can be prepared by heating the higher sulphides in a stream of hydrogen to a very high temperature1 and then forms pseudomorphs after these4#ddc ,it is a dark red metallic mass1 which reacts in the air only when heated1 forming the dioxide2 dilute acids and alkalies have no action on it1 concentrated nitric acid oxidises it slowly4 #ddb ,loc4 cit4 #ddc ,see v4 d4 ,pfordten 7loc4 cit472 ,thorpe1 ,chem4 ,news1 #ahhe1 #ea1 #bfj4 ,the dichloride1 ,ti,cl1 is obtained in the impure state as a black powder by decomposition of the trichloride at a red heat3 the tetrachloride is formed at the same time1 and volatilises4#ddd ,according to v4 d4 ,pfordten1#dde it is obtained by reduction of the tetrachloride by sulphuretted hydrogen or sodium amalgam in the cold4 ,the latter author states that it dissolves in alcohol or water in absence of air to a dark brown solution2 ,friedel and ,gurin1 however1 state that it acts energetically on these solvents with evolution of hydrogen1 forming a yellow solution4 ,when heated in the air it burns1 evolving fumes of the tetrachloride and leaving a residue of the dioxide4 ,the iodide1 ,ti,i1 has been obtained by ,defacq and ,copaux#ddf by reduction of the tetraiodide with silver or mercury1 as a black1 lustrous1 infusible sublimate4 ,it is insoluble in organic solvents1 but reacts with water and aqueous alkalies1 and is readily attacked by acids4 ,hydrogen at a bright red heat reduces it to amorphous titanium4 #ddd ,friedel and ,gurin1 ,compt4 rend4 #ahge1 #ha1 #hhi2 #ahgf1 #hb1 #eji1 #hgb4 #dde ,loc4 cit4 #ddf ,compt4 rend4 #aijh1 #adg1 #fe4 ,,compounds ,,of ,,trivalent ,,titanium4#ddg #ddg ,compounds of trivalent titanium are frequently referred to in ,english chemical and technical literature as #8,titanous ,compounds1' the salts of the tetravalent element being tacitly recognised as #8,titanic ,compounds4' ,in view of the existence of compounds of divalent titanium1 to which the name #8,titanous ,compounds' might be more logically applied1 the former nomenclature cannot be regarded as altogether satisfactory1 and it is therefore not adopted here4 ,these salts are obtained when the element is dissolved in hydrochloric and sulphuric acids1 and by reduction of the compounds of tetravalent titanium in solution by means of zinc and hydrochloric acid1 or by electrolysis4 ,according to ,diethelm and ,forster#ddh the reduction may also be effected by hydrogen in presence of finely divided platinum4 ,the salts have strong reducing properties1 transforming nitro-bodies to amines and decolourising azo-derivatives very rapidly2 they reduce unsaturated bodies1 and reduce dyes to the leuco-bases2 they reduce sulphurous acid to sulphur1 precipitate gold1 silver and mercury from their salts1 and reduce cupric and ferric salts to cuprous and ferrous compounds respectively4 ,the salts are green or violet in solution1 showing the phenomenon of hydrate-isomerism which is exhibited by the chromic salts2 they are to some extent hydrolysed in aqueous solution1 as shown by the acid reaction of the chloride4 ,they resemble the salts of ferric iron and aluminium in giving precipitates of basic salts when boiled with sodium acetate or sodium formate1 and in giving no precipitate with alkalies in the presence of organic hydroxy-acids4 ,ferrocyanide and ferricyanide give brown precipitates4 #ddh ,zeitsch4 physikal4 ,chem4 #aijh1 #fb1 #abi4 ,the hydroxide1 ,ti7,,oh71x,h,o1 is thrown down as a dark precipitate with strong reducing properties2 it attacks water with evolution of hydrogen1 forming the dioxide2 when an aqueous suspension is shaken with air1 autoxidation occurs1 hydrogen peroxide being formed4 ,the sesquioxide1 ,ti,o1 has been prepared by ,friedel and ,gurin#ddi by heating the dioxide to a white heat in a current of hydrogen and titanium tetrachloride2 it forms black lustrous crystals1 isomorphous with hmatite4 ,the sulphide1 ,ti,s1 is best obtained by reduction of the disulphide1 at a moderate temperature1 in a stream of hydrogen or nitrogen1 but is also prepared by the action of a mixture of carbon disulphide and sulphuretted hydrogen on the dioxide at a high temperature4 ,it is a dark grey metallic powder1 stable towards air1 water1 alkalies and dilute acids4 #ddi ,loc4 cit4 ,titanium ,nitride1 ,ti,n1 is obtained in all reduction processes in which titanium compounds are used1 if air or nitrogen is admitted2 it is formed when the element is heated in nitrogen1 and by the action of ammonia on the chloride4 ,it forms lustrous1 bronze-coloured leaflets1 which appear blue or violet when powdered4 ,it is extremely hard1 and very stable1 but is attacked by alkalies with evolution of ammonia4 ,it reduces the oxides of copper and lead in the fused state4 ,ruff and ,eisner have shown that it is a true nitride of the trivalent element1 and that only one nitride exists4#dej #dej ,ber4 #aije1 #ch1 #gdb2 #aijh1 #da1 #bbej4 ,the fluoride1 ,ti,f1 has been obtained as an insoluble violet powder by reduction of potassium titanofluoride1 ,k,ti,f1 with hydrogen4 ,from a solution it may be obtained by reduction of the same salt with zinc and hydrochloric acid1 or sodium amalgam4 ,it forms complex salts with alkali or ammonium fluoride1 of which the compound 7,,nh7,ti,f is an example2 this salt appears to be isomorphous with the analogous compounds1 7,,nh7,,vf1 7,,nh7,cr,f1 and 7,,nh7,fe,f4 ,by autoxidation in the air1 the solutions form fluoroxypertitanates4 ,the complex salts appear to exist in two forms1 a violet insoluble form and a green soluble modification4 ,the chloride1 ,ti,cl1 is obtained anhydrous by reduction of the tetrachloride--mercury1 silver1 and hydrogen being the most suitable agents4 ,heated in hydrogen1 it breaks up1 forming the tetrachloride and the dichloride2 heated in air it burns1 evolving the tetrachloride and leaving a residue of dioxide4 ,in solution1 in combination with alkali chlorides1 and as the solid hydrate1 it exists in the green and violet forms4 ,concentrated aqueous solutions deposit the violet hexahydrate1 ,ti,cl1#f;,h,o4 ,if such a solution be covered with ether1 and saturated at #j with hydrogen chloride1 the green modification is formed1 and may be extracted by the ether2 it is stable only in the presence of hydrochloric acid4 ,in the violet form1 all the chlorine is in the ionic condition1 and can be removed by silver nitrate2 similar determinations have not been made with the green form1 but it is most probable1 as in the case of the analogous chromic salts1 that only part of the chlorine content can be removed by silver nitrate4 ,bck and ,moser#dea have recently described a brown substance1 obtained by the action of the silent electric discharge on a mixture of hydrogen and the vapour of titanium tetrachloride at the ordinary temperature1 which they believe to be a monotropic modification of the ordinary violet trichloride2 the change of this brown form to the violet form is irreversible4 #dea ,monats4 #aiab1 #cc1 #iga2 #aiac1 #cd1 #ahbe4 ,the bromide and iodide resemble the chloride1 but are very unstable4 ,the sulphate1 ,ti7,,so71 is obtained as a green crystalline powder by heating with sulphuric acid the violet solution obtained by reduction of a solution of the dioxide in sulphuric acid4 ,it dissolves in dilute acids1 forming violet solutions4 ,with alkali sulphates it forms titanium alums1 which can be recrystallised from dilute sulphuric acid1 and have the general formulae1 properties1 and crystal form of the other alums4 ,an acid sulphate1 #c,ti7,,so71,h,,so1#be;,h,o1 is obtained by electrolytic reduction of a strongly acid solution of the dioxide in sulphuric acid1 or by treating the chloride repeatedly with hot dilute sulphuric acid4 ,it forms a crystalline violet powder1 with silky lustre1 insoluble in alcohol1 ether1 and #fj per cent1 sulphuric acid2 it dissolves slowly in water1 forming a violet solution4 ,when the aqueous solution is treated with excess 7#b molecules7 of alkali sulphate1 it forms sparingly soluble double sulphates1 which separate in bright blue crystals2 the compounds ,ti7,,nh77,,so71#i;,h,o1 and ,ti,rb7,,so71#ab;,h,o1 have been obtained in this way4 ,the ,use of ,salts of ,trivalent ,titanium in ,volumetric ,analysis4--,owing to their powerful reducing properties1 these salts have been proposed as very convenient reagents in volumetric analysis1#deb the chloride being most useful in this respect4 ,the estimations must be carried out in absence of air1 to avoid atmospheric oxidation2 generally the apparatus is filled with carbon dioxide4 ,the titanium solutions for use must also be preserved from the oxidising action of the air4 #deb ,see ,knecht1 ,ber4 #aijc1 #cf1 #aff2 ,knecht and ,hibbert1 ibid4 #aijc1 #cf1 #aedi2 #aije1 #ch1 #ccah2 #aijg1 #dj1 #chai4 ,for estimation of ferric salts1 an aliquot quantity is titrated directly with the titanium solution1 ammonium thiocyanate being used as indicator4 ,ferrous salts and ferric salts in the same solution are easily estimated by titrating the former with permanganate solution1 or better with hydrogen peroxide1 and then estimating the total ferric salt with the titanium solution4 ,oxidising agents like nitrates and chlorates can be estimated in acid solution by treatment with an excess of a ferrous salt1 and estimation of the ferric compound formed by means of titanium4 ,azo-bodies and organic dyes can be titrated directly1 if soluble in hydrochloric acid1 the disappearance of colour marking the end of the reaction2 nitroso-compounds can also be estimated in this way4 ,if the compound is insoluble1 it may be reduced in hydrochloric acid suspension with excess of the titanium salt1 and the excess then determined by means of ferric iron4 ,insoluble dyes may also be converted into soluble sulphonic acids1 and estimated directly in solution4 ,ammonium persulphate may be estimated by reduction with excess of the chloride1 and back titration of the excess with ferric iron4 ,hydrogen peroxide may be estimated directly1 the disappearance of the yellow colour formed at the first addition marking the end of the reaction4 ,tin may be estimated by addition of an excess of a ferric salt1 and estimation of the excess by titanium in the usual way4 ,cupric salts also may be estimated directly1#dec the end point being reached when the bluish-green solution becomes colourless4 #dec ,moser1 ,chem4 ,zeitg4 #aiab1 #cf1 #aabf4 ,,compounds ,,of ,,tetravalent ,,titanium ,the compounds of tetravalent titanium are much more stable than the compounds in which the element has a lower valency1 and are very readily formed from them4 ,the dioxide is amphoteric in character1 and acts as a weak acid as well as a weak base2 the salts it forms with acids as well as those it forms with bases are very easily hydrolysed1 with separation of the hydrated oxide4 ,titanium salts1 therefore1 can only be held in solution by a considerable excess of acid4 ,the tendency to the formation of complex compounds is very pronounced1 particularly in the case of the fluoride1 oxalate and tartrate4 ,the hydroxide1 or hydrated oxide1 is capable of existing in two modifications1 according to the conditions under which it is thrown down1 though the two can hardly be said to be very definitely differentiated4 ,the or ortho form is obtained as a voluminous white precipitate by the addition of ammonia or alkali hydroxide in the cold to a freshly prepared solution of a titanium salt4 ,it is insoluble in water and alcohol1 but dissolves readily in dilute mineral acids1 and to some extent also in dilute alkalies4 ,the water content is very variable1 and no definite hydrate or hydroxide can be prepared2 when the substance is heated1 it loses water continuously1 and at a definite temperature glows1 doubtless by reason of some polymeric change4 ,if it be maintained for some time at a temperature somewhat below the normal temperature of glowing1 this phenomenon no longer occurs when the temperature is further raised4 ,the modification1 or metatitanic acid1 as it is called1 is obtained by hydrolysis of the salts by boiling1 or by addition of alkali at #ajj1 as a fine white precipitate4 ,it is almost insoluble in dilute acids and alkalies1 but dissolves in water to a colloidal solution2 when heated it does not glow4 ,the form is also obtained when the metatitanates are treated with water2 these compounds hydrolyse very readily1 but the precipitated dioxide carries down alkali by adsorption4 ,the dioxide1 ,ti,o1 occurs crystalline in nature in the three forms ,rutile1 ,brookite1 and ,anatase1 all of which can be prepared by laboratory methods2#ded the amorphous form is obtained by ignition of the hydrated oxide1 and of suitable salts4 ,the oxide melts at #aefj1 forming a mobile 787 liquid of density #da2 for the physical properties1 see the accounts of the naturally occurring forms in ,chapter ,v4 ,when heated in a current of hydrogen or carbon monoxide1 it gives rise to intermediate oxides1 ,ti,o1 ,ti,o1 etc41 which are not very well known1 and are of doubtful individuality4 ,it reacts when heated in chlorine1 and with many non-metallic chlorides1 forming the tetrachloride2 with carbon disulphide at high temperatures it gives the disulphide1 ammonia at a red heat forms the nitride4 ,it is exceedingly resistant to acids1 but is attacked slowly by boiling sulphuric acid1 more quickly by fused bisulphate4 #ded ,see p4 #gi2 also ,hautefeuille1 ,ann4 chim4 phys4 #ahfc1 iv41 #d1 #abi4 ,titanium disulphide1 ,ti,s1 is obtained in the pure state when a mixture of the vapour of the tetrachloride and sulphuretted hydrogen is led through a strongly heated porcelain tube4 ,it is a fairly stable substance1 forming metallic crystals which yield the dioxide when heated in air4 ,when heated in a stream of hydrogen or nitrogen it yields one or other of the lower sulphides according to the temperature employed4 ,it is not attacked by water1 but dissolves in acids1 and is decomposed by boiling potash1 forming a titanate2 it is insoluble in alkali sulphides4 ,the carbide1 ,ti,c1 was prepared by ,moissan by heating the oxide with carbon in the electric furnace2 any excess of carbon separates on cooling as graphite4 ,it has the density #dbe1 and resembles the fused element in appearance4 ,it dissolves in nitric but not in hydrochloric acid4 ,titanium tetrafluoride1 ,ti,f1 is obtained by the action of fluorine on the element or the carbide1 and by the action of anhydrous hydrofluoric acid on the element or the tetrachloride4 ,it is a white powder1 and boils at #bhd2 it is very hygroscopic1 and dissolves easily in alcohol and water1 showing little tendency to form basic salts4 ,from the concentrated aqueous solution it separates as the dihydrate1 ,ti,f1#b;,h,o2 basic salts are obtained only by repeated evaporation with water4 ,the anhydrous compound forms additive products with ammonia and with pyridine4 ,with aqueous hydrofluoric acid it forms the complex ,h,ti,f1 as shown by conductivity measurements1 and the fact that only a slow and incomplete precipitation of the hydroxide is effected by addition of ammonia4 ,the solution dissolves metallic oxides and carbonates1 forming titanofluorides1 which are for the most part isomorphous with the corresponding silicofluorides1 stannofluorides1 and zirconofluorides4 ,they are very stable crystalline salts1 of the general formula ,r,ti,f2 many salts of the types ,r,ti,f1 ,r,ti,f1 etc41 have been prepared4 ,the most important is the potassium salt1 ,k,ti,f1 which crystallises from acid solutions in monoclinic tablets2 from aqueous solution it separates as the monohydrate1 ,k,ti,f1,h,o1 isomorphous with the compounds ,k,cb,o,f1,h,o and ,k,,wo,f1,h,o4 ,the hydrate loses its water at #ajj1 and melts at a white heat without decomposition4 ,it is moderately soluble in hot1 very sparingly soluble in cold water1 and hence is readily recrystallised4 ,the tetrachloride1 ,ti,cl1 is important1 on account of its low boiling-point1 for the separation and purification of titanium compounds4 ,in physical as well as chemical properties1 it resembles the chloride of a non-metallic element rather than a normal salt1 and is distinguished by the ease with which it combines or reacts with the most widely differing organic compounds4 ,it is prepared by the action of chlorine upon the element1 the carbide1 or a mixture of the dioxide with carbon1 and by the action of chloroform or carbon tetrachloride upon the dioxide at a bright red heat4 ,it is a colourless1 transparent liquid1 of density #agf at #j2 it freezes at -#bc1 and boils at #acf under atmospheric pressure4 ,in moist air it fumes excessively1 yielding hydrogen chloride by hydrolysis3 ,ti,cl ,h,o ,ti,o,cl #b;,h,cl1 and is decomposed by water with separation of the hydrated oxide4 ,if the compound be added slowly to a large quantity of cold water1 and the clear solution warmed1 the oxide formed by hydrolysis remains in colloidal solution4 ,the chloride dissolves in fuming hydrochloric acid1 forming a deep yellow solution1 which becomes colourless when diluted4 ,the solution appears to contain the unstable complex acid ,h,ti,cl1 or its ions2 by addition of ammonia1 or organic bases1 salts of the type 7,,nh7,ti,cl can be obtained as yellow crystalline solids4 ,an interesting property of the chloride is its ability to form stable additive compounds with the chlorides of negative elements4 ,a long series of these are known1 of which the compounds ,ti,cl1,p,cl1 ,ti,cl1,p,cl1 ,ti,cl1,p,o,cl1 and ,ti,cl1#b,p,o,cl may be considered examples2 for the most part1 they can be distilled without decomposition4 ,a very long series of compounds1 partly additive and partly condensation products1 with all kinds of organic substances1 is also known4 ,a series of oxychlorides1 or basic chlorides1 ,ti,cl7,,oh71 ,ti,cl7,,oh71 and ,ti,cl7,,oh71 has been obtained by addition of hydrochloric acid1 in certain quantities and concentrations1 to the chloride2 they are amorphous solids1 of which little is known4 ,the tetrabromide1 ,ti,br1 is a yellow crystalline solid1 melting at #ci and boiling at #bcj4 ,its solutions in concentrated hydrobromic acid are of a blood-red colour1 and by treatment with ammonia and organic bases yield deep red crystalline salts of the type 7,,nh7,ti,br4 ,the tetraiodide1 ,ti,i1 is a reddish-brown metallic-looking solid1 melting at #aej1 and boiling at #cfj2 no complex salts are known4 ,the sulphates4--,many compounds of doubtful composition and individuality have been described as titanium sulphates1 but relatively little is known with certainty of this class of derivatives4 ,the most stable seems to be the titanyl sulphate1 ,ti,o,s,o1 obtained as a white powder1 which is slowly hydrolysed by water1 by evaporating a solution of the dioxide in concentrated sulphuric acid4 ,under suitable conditions1 e4g4 when separated from acid or alcoholic solutions1 it is said to form hydrated compounds2 the mono-1 di- and penta-hydrate have been described4 ,when solutions of this compound in concentrated sulphuric acid are treated with concentrated aqueous solutions of alkali sulphates1 salts of the formul 7,,nh7,ti,o7,,so71,h,o and ,k7,ti,o77,,so71#aj;,h,o1 are obtained4 ,by treating solutions of the dioxide in a large excess of concentrated acid with solutions of calcium or strontium sulphate in sulphuric acid1 salts of the type ,r,ti7,,so7 are obtained2 the barium salt has the formula #c,ti7,,so71#b;,ba,s,o4 ,all these compounds are rapidly hydrolysed by water4 ,phosphoric ,acid ,derivatives4--,solutions of titanium compounds are completely precipitated by the addition of phosphoric acid1 or soluble phosphates1 even in presence of a large excess of mineral acid1 but the composition of the precipitate obtained is unknown4 ,by heating the oxide with orthophosphoric acid1 a crystalline compound1 ,ti,o1,p,o1 is obtained1 and various alkali double phosphates may be prepared by suitable fusions4 ,concentrated aqueous oxalic acid solutions readily dissolve one equivalent of titanium dioxide1 forming greenish-yellow solutions which contain titanyl oxalate1 ,ti,o7,c,o74 ,from alcoholic solution1 this substance can be precipitated by ether as the alcoholate1 ,ti,o7,c,o71,c,h,,oh1 a micro-crystalline precipitate soluble in water and alcohol4 ,titanyloxalic acid1 ,ti,o7,,hc,o71,h,o1 and its salts are stable compounds2 the latter are obtained by dissolving the dioxide in alkali binoxalate1 the acid itself being obtained by treatment of the sparingly soluble barium salt with sulphuric acid4 ,complex acids are also formed with tartaric acid1 and other organic hydroxy-acids2 from its solutions in these acids1 the dioxide cannot be again precipitated by boiling1 or by addition of alkalies4 ,titanates and ,pertitanates4--,on account of the weakly acid character of the dioxide1 stable titanates can be prepared only in the dry way4 ,the dioxide resembles silica in the conditions under which it forms salts1 and in the nature1 and generally the crystallographic properties1 of the products obtained4 ,the commonest salts are the metatitanates of the formulae ,r,ti,o and ,r,ti,o1 which are obtained by fusing the dioxide with metallic oxides and carbonates1 sometimes with addition of a suitable agent to act as a crystallising medium1 e4g4 sodium tungstate1 calcium chloride1 magnesium chloride1 etc4 ,calcium metatitanate1 ,ca,ti,o1 prepared by heating titanium dioxide with calcium carbonate in presence of calcium chloride1 is identical in properties with the naturally occurring compound1 ,perovskite 7q4v474 ,orthotitanates of divalent metals only are known2 these have the general formula ,r,ti,o1 and are prepared by similar methods4 ,the iron compound ,fe,ti,o is also identical in properties with the mineral ilmenite1 and isomorphous with the sesquioxides ,fe,o1 ,ti,o4 ,magnesium titanates of both the ortho type 7,mg,ti,o7 and the meta type 7,mg,ti,o7 have been prepared in the laboratory2 the latter is identical with the mineral ,geikielite 7q4v474 ,the compounds prepared in this way are all insoluble in water1 doubtless by reason of the slowness with which such compact solids can be attacked2 they dissolve easily in dilute acids4 ,the weakly acid character of titanium dioxide is shown by the fact that if the fusion with metallic carbonates be carried out in vessels so adjusted that the carbon dioxide exerts a pressure of one atmosphere1 a condition of equilibrium is reached1 in which a considerable part of the carbonate remains unattacked4 ,in the presence of hydrogen peroxide1 however1 the acidic properties are considerably strengthened1 and the per-salts can be obtained in the wet way4 ,addition of hydrogen peroxide to a neutral or acid solution of a titanium compound gives a yellow colour1 due to the formation of a peroxide1 ,ti,o1aq4 ,such solutions have the same oxidising powers as hydrogen peroxide1 but do not give the blue colouration with chromium salts4 ,by treatment of the solution with dilute alkalies1 an hydrated peroxide is thrown down1 which1 when dried over phosphoric anhydride1 has the formula ,ti,o1#c;,h,o1 and forms a yellow1 horny mass4 ,the freshly precipitated peroxide dissolves in acids and alkalies2 from the latter solutions1 by addition of hydrogen peroxide and alcohol1 pertitanates of various composition can be obtained1 of which the following are examples 3 ,na,o1,ti,o1#c;,h,o2 7,,nh7,o1,ti,o1,h,o2 ,ba,o1,ti,o1#e;,h,o2 ,k,o1,k,o1,ti,o1#aj;,h,o1 etc4 ,these salts lose hydrogen peroxide when treated with dilute acids1 and their constitutions are unknown4 ,an interesting series of fluoroxypertitanates has been prepared by oxidation of the solution of titanium dioxide in hydrofluoric acid with hydrogen peroxide1 and addition of metallic fluorides4 ,the ammonium compound1 7,,nh7,ti,o,f1 crystallises in yellow octahedra1 isomorphous with the salts ,zr,f1#c,,nh,f and ,cb,o,f1#c,,nh,f4 ,the potassium salt1 ,k,ti,o,f1 crystallises well from water1 and is easily obtained in the pure state2 various barium salts are known4 ,similar compounds with oxalic acid have also been prepared4 ,atomic ,weight of ,titanium4--,the first reliable determinations of this constant were carried out by ,h4 ,rose in #ahbi4 ,he determined the ratio ,ti,cl 3 #d;,ag,cl1 by dissolving the pure tetrachloride1 weighed in sealed glass bulbs1 in water in closed flasks1 precipitating the dioxide by ammonia1 and weighing the silver chloride obtained by adding silver nitrate to the filtered and acidified solution4 ,he obtained the values #dhbg and #dhac1 which agree very well with the accepted value1 #dha4 ,in the same year1 ,mosander1 using a method not specified1 obtained the value #dgae4 ,determinations carried out by ,pierre 7#ahdg7 and ,demoly 7#ahdi7 led to widely varying results4 ,a series of determinations carried out by ,thorpe during the years #ahhc-ahhe gave consistent results4 ,the method used was the precipitation of silver halide from the tetrachloride and tetrabromide1 and the mean value of seven series of determinations gave the number #dhjh4 ,the ,international ,committee have adopted this result as the basis of the accepted value1 #dha4 ,detection4--,the specific reactions for the element are frequently masked by the presence of other metals1 especially of iron1 columbium1 tantalum1 and vanadium1 which most frequently accompany it in nature1 and from which a quantitative separation is frequently very difficult 7see p4 #cch74 ,the most characteristic reactions are the following3 7#a7 ,reduction in acid solution by means of tin or zinc gives an intense violet colour1 due to the formation of trivalent titanium salts4 ,various colours are given by vanadium1 columbium1 and tungsten1 so that the test is not decisive if these are present4 7#b7 ,hydrogen peroxide in acid solution gives a reddish-yellow colour1 which is very delicate1 and is used in quantitative estimation2 vanadium compounds interfere4 7#c7 ,in sulphuric acid solution1 characteristic colours are obtained with many phenolic compounds2 thymol gives a blood-red colour which is exceedingly intense4 7#d7 ,a very characteristic and intense colour is given in acid solution on the addition of #a3h-;dihydroxynaphthalene-#b3d-;disulph onic acid 7chromotropic acid74 ,the methods for the estimation of titanium are given in ,chapter ,,xxii4 ,,chapter ,,xvi ,,the ,,group ,,iva ,,elements 7continued7--,,zirconium ,,and ,,thorium ,zirconium1 ,zr #ijf ,the oxide zirconia was isolated as a new earth from zircon from ,ceylon by ,klaproth in #aghi2 six years later the new earth was obtained also from hyacinth1 the gem-variety of the same mineral4 ,the new oxide was examined in #ahah by ,berzelius1 who pointed out its resemblance to alumina1 and gave it the formula ,zr,o2 during the next two decades he thoroughly investigated its properties1 preparing the element itself1 and determining its equivalent4 ,in #aheg a determination of the vapour density of the chloride1 by ,deville and ,troost1 showed that the element is really tetravalent1 and that the formula ,zr,o must be assigned to the oxide2 this formula was shown to accord with the isomorphism of rutile 7,ti,o7 and zircon 7,zr,o1,si,o7 by ,rose in #ahei1 whilst in the following year ,marignac observed the isomorphism between the fluozirconates of zinc and nickel and the fluosilicates1 fluotitanates1 and fluostannates of these metals4 ,the homogeneity of the oxide has been questioned2 ,svanberg in #ahde considered it to be a mixture of at least three earths1 whilst ,sorby and ,forbes in #ahfi claimed to have discovered in it a new oxide1 #8,jargonia4' ,these claims1 however1 have been shown to have been founded on inaccurate experimental work1 and the individuality of the element is at the present time considered to be well established4 ,zirconium is fairly widely distributed in nature1 but generally in very small quantities1 and can be rightly classed as one of the rarer elements4 ,it occurs in some silicates1 and in small quantities in almost all the rare earth minerals4 ,the most important source of the element and its compounds was until quite recently the mineral ,zircon1 with its gem-varieties ,hyacinth and ,jargon1 and the large number of secondary altered zircon minerals4 ,since its discovery in #ahib1 however1 the naturally occurring oxide1 ,baddeleyite1#dee has become increasingly important for the extraction of zirconium compounds1 especially for the preparation of the pure oxide for fire-resistant materials4 #dee ,for accounts of the zircon minerals1 see pp4 #dg and #ge1 and the alphabetical list4 ,the minerals may be treated by any of the usual methods4 ,zircon may be fused with alkali or alkali carbonate2 the cooled melt is extracted with water1 and the insoluble alkali zirconate decomposed by dilute acids2 from the solution1 zirconia is thrown down by alkalies4 ,potassium hydrogen fluoride and potassium hydrogen sulphate may be used for the treatment either of zircon or of baddeleyite2 in the first case1 the potassium fluozirconate formed may be dissolved by boiling with dilute hydrofluoric acid1 and separates out readily on cooling1 whilst the fluosilicate formed is not dissolved2 the second treatment yields the sulphate1 which may also be dissolved out by dilute acid4 ,a very convenient method consists in reducing with carbon1 either alone or in presence of lime1 at the temperature of the electric arc2 the infusible zirconium carbide is formed1 whilst silica1 if present1 is reduced to the carbide1 which is volatile at that temperature and is therefore driven off4 ,the zirconium carbide may be dissolved in warm aqua regia4 ,in all these methods the compounds obtained are contaminated with iron1 which clings to zirconium very tenaciously4 ,many methods have been devised for its removal4 ,a very suitable method is the thiosulphate precipitation4 ,zirconia is thrown down quantitatively1 mixed with sulphur1 from a not too strongly acid solution by addition of sodium thiosulphate at the boiling-point1 sulphur dioxide being at the same time evolved1 by decomposition of the potential thiosulphuric acid formed by hydrolysis4 ,thorium and titanium accompany the zirconium1 but iron1 aluminium1 and the rare earths remain in solution4 ,another method depends on the fact that zirconium is not precipitated from alkaline solution by ammonium sulphide in the presence of tartaric acid1 whereas this reagent does not inhibit the precipitation of ferrous sulphide4 ,iron may also be removed from a solution in concentrated hydrochloric acid by means of ether1 in which medium ferric chloride is easily soluble4 ,zirconium compounds may be obtained free from iron by repeated crystallisations of the oxychloride4 ,zirconium forms only one series of compounds1 in which the metal is tetravalent4 ,its chemical behaviour accords well with its position in the periodic classification4 ,it is somewhat more electropositive than titanium1 as shown by the fact that the hydroxide will not dissolve in alkalies1 though zirconates may be obtained by the fusion methods2 the oxide1 however1 is still a weak base1 and the salts are to a large extent hydrolysed in solution4 ,the formation of a stable oxychloride1 which can be recrystallised without change in composition1 shows clearly the strengthening of the electropositive character4 ,it has still1 however1 in a high degree1 the property of forming complex salts1 which is characteristic of the less electropositive metals4 ,the group relations are borne out by the isomorphism of many related salts4 ,the hydroxide and oxide show polymeric modifications1 and the former has the usual tendency of compounds of this group to form colloidal solutions1 a tendency which extends to the element itself4 ,the metal resembles titanium in the eagerness with which it combines with other elements1 especially with oxygen1 nitrogen1 and carbon1 whilst the chloride closely resembles titanium tetrachloride in general properties1 and in the ease with which it forms addition and condensation products with other substances4 ,the ,metal4--,all the difficulties which attend the attempts to prepare metallic titanium in the pure state have to be encountered in the preparation of metallic zirconium4 ,the attempts which have been made have used the same methods1 and obtained much the same kind of result as those employed in the case of titanium4#def ,the reduction of potassium fluozirconate by metallic potassium1 first employed by ,berzelius1 gives an amorphous product of unknown metal-content2 it certainly contains a considerable percentage of oxygen4 ,the monoxide is obtained when zirconia is reduced by magnesium 7,winkler's method74 ,the reduction of the fluozirconates of potassium by means of sodium gives better results if the reaction is carried out in presence of sodium chloride in a sealed iron bomb2 the product after careful washing contains #ig-ih per cent4 of the metal4 ,reduction with aluminium leads to the formation of alloys2 ,weiss and ,neumann#deg have used these in the form of pencils as electrodes between which they pass the electric arc in vacuo1 and so obtain an almost pure zirconium4 ,the #ig-ih per cent4 amorphous product obtained by the sodium reduction also yields the practically pure metal when treated in this way 7compare ,titanium1 p4 #bbc74 ,a very pure zirconium has been obtained by ,wedekind#deh by heating the oxide with fine calcium turnings in an evacuated iron tube2 the powdered product is washed1 in absence of air1 and heated in an evacuated porcelain tube to #hjj-ajjj1 at which temperature the powder sinters into lumps which take a brilliant polish and contain #iia per cent4 of the metal4 ,attempts to prepare a purer product from this by the method of ,weiss and ,neumann were unsuccessful4 #def ,for a detailed account of these1 see ,lewis1 ,studien ber das elementare ,zirconium1 ,stuttgart1 #aiab4 #deg ,zeitsch4 anorg4 ,chem4 #aiji1 #fe1 #bdh4 #deh ,annalen1 #aiac1 #cie1 #adi4 ,the amorphous metal is a dark powder1 which when washed with water on the filter paper passes through as a dark blue colloidal solution2 it burns readily when heated in the air4 ,according to ,wedekind and ,lewis1#dei amorphous zirconium is really the colloidal form of the metal4 ,the fused metal is very hard 7#g-h1 ,mohs' scale--it scratches quartz but not topaz7 and very brittle2 it has the density #fd1 and is of a whitish colour1 with good metallic lustre on freshly broken surfaces4 ,the atomic heat is abnormally high1 being approximately #gc2 the element is paramagnetic4 ,the melting-point was given by ,wedekind and ,lewis#dfj as #bccj-bchj1 but later work of the former author#dfa gives the much lower value of #aecj1 which seems more probable in view of the fact that the element cannot be employed for electric lamp filaments 7see p4 #cbb74 #dei ,ibid4 #aiaj1 #cga1 #cfg4 #dfj ,weiss and ,neumann1 loc4 cit42 also ,wedekind1 loc4 cit4 #dfa ,annalen1 #aiac1 #cie1 #adi4 ,metallic zirconium is highly resistant to acids2 it is attacked only by hydrofluoric acid and by aqua regia4 ,in the compact form it burns in the air only at very high temperatures1 though when powdered it glows in the air at a red heat1 forming probably a mixture of lower oxides4 ,it is attacked by chlorine and by hydrogen chloride at a red heat1 with formation of the chloride2 fused potash also oxidises it1 with evolution of hydrogen4 ,when heated in a current of hydrogen at a red heat1 it forms the hydride1 ,zr,h1#dfb as a velvet-black powder1 which burns with an intense bluish flame in oxygen1 forming the sesquioxide1 ,zr,o4 ,when heated in nitrogen or ammonia1 amorphous zirconium yields nitrides1 which are also obtained when any attempt is made to reduce zirconium compounds to the metal in air4 ,the most definite is the compound ,zr,n1#dfb which forms a bronze-coloured powder1 resistant to all mineral acids except hydrofluoric acid4 ,chlorine and bromine transform this to the halide4 #dfb ,wedekind and ,lewis1 ,annalen1 #aiaj1 #cga1 #cfg4 ,the hydroxide is of doubtful individuality1 since on drying it loses water progressively as the temperature is raised1 no definite stable compound being known2 in this respect zirconium resembles titanium4 ,when heated to #ajj1 its composition corresponds approximately with that required by the formula ,zr,o1,h,o1 but the percentage of water varies with the history of the specimen4 ,when precipitated by alkalies in the cold1 it forms the so-called or ortho modification1 which1 like the analogous titanium compound1 is readily soluble in dilute acids1 and glows when heated4 ,by precipitation at the boiling point1 the form is obtained2 this is less soluble in acids1 and does not glow when heated4 ,the differences between the two forms are by no means sharply marked2 they are rather the limiting forms of a continuously varying series than distinct chemical individuals1 and the properties of any hydroxide precipitate depend very largely on the conditions under which it is thrown down4 ,the hydroxide is insoluble in water1 but can be obtained in colloidal solution after it has been repeatedly heated with dilute acids1 which serve to break down the molecular complexes2 it can be also readily obtained in colloidal solution by dialysis of the nitrate1 chloride1 or acetate4 ,in these solutions it is positively charged2 electrolytes precipitate it with great ease4 ,the gel has a very high power of forming adsorption products4 ,when thrown down from solution by soda or potash1 it carries down considerable quantities of alkali1 to which it clings so tenaciously that the most careful washing cannot entirely remove them4 ,if the gel be placed in contact with an ammoniacal solution of a cupric compound1 it removes the cuprammonium complex entirely from the solution1 becoming itself deep blue in colour1 and leaving the liquid quite clear and colourless4 ,in colloidal solution it forms adsorption compounds with negatively charged colloids1 especially metals1 the gels obtained from such solutions containing both colloids4 ,in the presence of hydrogen peroxide1 ammonia throws down an hydrated peroxide1 which is also obtained#dfc by electrolysis of a brine solution in which the hydroxide is suspended1 oxidation being effected by the sodium hypochlorite formed4 ,this reaction is expressed by the equation3 ,zr7,,oh7 ,na,o,cl ,zr7,,ooh77,,oh7 ,na,cl #dfc ,pissarjewski1 ,zeitsch4 anorg4 ,chem4 #aijj1 #be1 #cgh4 ,it is an endothermic compound1 and is very unstable1 losing oxygen on standing2 by the action of acids it gives hydrogen peroxide4 ,it dissolves in alkalies containing hydrogen peroxide2 from such solutions1 alcohol precipitates salts of the formula ,r,zr,o1#i;,h,o4 ,zirconium oxide1 ,zr,o1 occurs in nature2 it can be obtained in the laboratory as a voluminous white powder by ignition of the hydroxide or a suitable salt4 ,the physical properties are described under the mineral ,baddeleyite 7p4 #ge7 and in ,chapter ,,xxi 7p4 #cbc71 in which an account of its technical applications is given4 ,the melting-point is probably about #bgjj2 at #cjjj it begins to volatilise4 ,it dissolves readily in mineral acids1 unless previously ignited very strongly2 all specimens dissolve easily in hydrofluoric acid1 and are readily converted by concentrated sulphuric acid into the sulphate4 ,when fused with metallic oxides or carbonates1 it gives crystalline zirconates1 of which a large number have been prepared2 the calcium compound1 ,ca,zr,o1 is said to be isomorphous with perovskite1 ,ca,ti,o4 ,a suboxide1 ,zr,o1 of somewhat doubtful individuality1#dfd is said to be obtained when the dioxide is reduced with magnesium2 it forms a dry black powder1 which is not attacked by acids1 and when heated glows1 forming the dioxide4 ,a sesquioxide1 ,zr,o1 is obtained as a greenish powder when the hydride is burnt in oxygen2 when heated in the air1 it oxidises very slowly1 forming the dioxide4 #dfd ,wedekind and ,teletow 7,annalen1 #aiac1 #cie1 #adi7 have recently denied the existence of this oxide4 ,an oxysulphide1 ,zr,o,s1 is obtained when the anhydrous sulphate is heated in a current of sulphuretted hydrogen2 it is a bright yellow powder1 which ignites spontaneously in the air4 ,no disulphide is known4 ,the carbide1 ,zr,c1 is obtained1 according to ,moissan and ,lengfeld1#dfe when the oxide is heated with carbon in any proportions1 excess of carbon separating on cooling as graphite2 the process is hastened by addition of lime4 ,it is a hard1 dark-grey solid1 and is a very good conductor of electricity4 ,when heated in oxygen or nitrogen1 it reacts readily1 forming the oxide and nitride respectively2 halogens attack it at quite low temperatures 7#bej-djj71 forming the halide compounds1 which are indeed best prepared in this way4 ,strong mineral acids1 with the exception of hydrochloric acid1 attack it1 and fused alkalies dissolve it readily4 #dfe ,compt4 rend4 #ahif1 #abb1 #fea4 ,the fluoride1 ,zr,f1 is best obtained by the action of anhydrous hydrofluoric acid on the chloride4 ,it forms a white crystalline mass1 which readily sublimes1 and is soluble in hydrofluoric acid2 from the solution it crystallises as the trihydrate1 ,zr,f1#c;,h,o4 ,the anhydrous substance is very slightly soluble in water in the cold2 when warmed1 it hydrolyses1 forming the hydroxide4 ,the solution in hydrofluoric acid dissolves metallic carbonates and oxides1 forming the numerous fluozirconates or zirconofluorides4 ,there are many types of these compounds1 of which the potassium salt1 ,k,zr,f1 is the most important4 ,the solubility of this salt increases very rapidly with the temperature2 #ajj parts of water dissolve1 at #ae1 #ada parts1 at #ajj1 #be parts of the compound4 ,it has been frequently used for the purification of zirconium compounds1 for the preparation of the element1 and for analytical determinations4 ,other potassium salts1 ,k,zr,f and ,k,zr,f1,h,o1 are obtained by using a large excess of potassium fluoride and zirconium fluoride respectively4 ,the ammonium compounds are analogous in composition to the potassium salts1 but the sodium salt1 ,na,zr,f1 is obtained from mixtures of the components in all proportions2 on account of its very low solubility1 it can be obtained by double decomposition of the potassium salt with sodium chloride4 ,of the salts with divalent metals1 the types ,r,zr,f1x,h,o and ,r,zr,f1x,h,o1 are the most common4 ,the chloride1 ,zr,cl1 is known1 on account of the ease with which it hydrolyses1 in the anhydrous state only4 ,it can be obtained by all the usual methods1 of which perhaps the action of chlorine on the carbide1 and of carbon tetrachloride1 or a mixture of chlorine and sulphur monochloride1 on the oxide1 are the most convenient2 an interesting method consists in heating the oxide with phosphorus pentachloride in a closed tube at #aij4 ,it forms a volatile white sublimate1 which fumes strongly in air1 and reacts vigorously with water2 it is soluble in ether4 ,it forms a series of addition compounds with ammonia and organic bases1 as well as with the chlorides of non-metallic elements2 warmed with phosphorus pentachloride1 it forms a stable solid1 #b,zr,cl1,p,cl1 which melts at #bdj1 and boils at #cde4 ,with organic compounds1 especially with esters1 acids1 and phenols1 it forms a long series of addition and condensation products1 of which the compounds ,zr,cl7,c,h,,cooc,h7 and ,zr,cl,o,c,h,,cho may be taken as examples4 ,by addition of organic bases to a solution of the chloride in alcoholic hydrogen chloride1 double chlorides of the type 7,c,h,,nh7,zr,cl are obtained4 ,the oxychloride1 ,zr,o,cl1#h;,h,o1 separates in characteristic tetragonal prisms when the tetrachloride is dissolved in water or hydrochloric acid of any concentration4 ,it is readily soluble in water and alcohol1 but sparingly soluble in hydrochloric acid1 from which therefore it is generally recrystallised4 ,according to ,chauvenet1#dff it effloresces in dry air1 forming the hexahydrate1 ,zr,o,cl1#f;,h,o2 when dried in a vacuum1 it forms the hydrate1 ,zr,o,cl1#c;,h,o1 whilst the dihydrate1 ,zr,o,cl1#b;,h,o1 is obtained by heating at #ajj-aje in hydrogen chloride4 ,when the dihydrate is heated to #bcj1 it forms another basic chloride1 ,zr,o,cl,zr,o1#dfg which is stable up to #fjj2 above this temperature1 it breaks up1 forming the volatile tetrachloride1 and leaving a residue of the dioxide4 #dff ,compt4 rend4 #aiab1 #aed1 #hba4 #dfg ,ibid4 #abcd4 ,by repeated evaporation of the oxychloride with small quantities of water1 a #8metazirconium chloride' is obtained1 which dissolves in water to a colloidal solution1 and on dialysis yields a colloidal solution of #8metazirconic acid4' ,the bromide1 ,zr,br1 very closely resembles the chloride2 when treated with water it forms the oxybromide1 which separates from solution according to the conditions in various hydrated forms1 of which the commonest is the octohydrate1 ,zr,o,br1#h;,h,o4 ,the iodide1 ,zr,i1 is a very reactive body1 which closely resembles the preceding2 it forms an oxyiodide1 ,zr,o,i1#h;,h,o4 ,zirconyl chlorate1 ,zr,o7,cl,o71#f;,h,o1 is obtained from the sulphate by double decomposition with barium chlorate2 it forms very soluble colourless needles4 ,alkali iodates or iodic acid throw down a voluminous oxyiodate1 very sparingly soluble1 like the corresponding ceric and thorium salts1 in water and acids4 ,the ,sulphates4--,when zirconium dioxide is dissolved in concentrated sulphuric acid1 and the excess of acid removed by heating to #djj1 the #8neutral' sulphate1 ,zr7,,so71 remains4 ,the compound dissolves in dilute sulphuric acid to form solutions which contain various #8complexes' as shown by conductivity measurements1 and the behaviour towards oxalic acid4 ,whilst solutions of the nitrate or chloride give immediate precipitates with this reagent1 solutions of the #8sulphate' give no precipitate1 or at most a very gradual one2 moreover1 addition of sulphuric acid or of alkali sulphates to other zirconium salts inhibits the oxalate precipitation4 ,these facts are explained by regarding the #8neutral' sulphate1 ,zr7,,so71#d;,h,o1 as zirconylsulphuric acid1 ,zr,o,s,o1,h,,so1#c;,h,o1 which in solution ionises to #b;,h4 and ,zr,o,s,o1,,so4 ,this conclusion is confirmed by the fact that whilst in solutions of the chloride in hydrochloric acid1 zirconium goes on electrolysis to the cathode1 on addition of sulphuric acid to the solution it travels to the anode4 ,the anhydrous compound and the hydrate are extremely soluble in water1 but much less readily soluble in dilute sulphuric acid4 ,probably in solution more complex salts are formed by further hydrolysis1 for by addition of concentrated alkali sulphate solution in the cold1 double salts of the formula ,zr,o7,,rso71#h;,h,o are obtained4 ,when the solution is kept for some time at #ci-dj1 a basic sulphate1 #d,zr,o1#c,,so1#ad;,h,o1 separates slowly4 ,when concentrated solutions are boiled1 a salt1 #b,zr,o1#c,,so1#e;,h,o1 separates as a crystalline precipitate2 in contact with water it slowly hydrates itself to the compound #b,zr,o1#c,,so1#ad;,h,o2 when heated to #cjj1 it becomes anhydrous without further change4 ,various other basic1 acid and complex salts have also been described4 ,the nitrate1 ,zr7,,no71#e;,h,o1 separates from concentrated solutions of the oxide in nitric acid by evaporation over sulphuric acid and sodium hydroxide2 it is believed to be a zirconylnitric acid1 ,zr,o7,,no71#b;,,hno1#d;,h,o by analogy with the sulphate4 ,when its aqueous solutions are warmed1 basic salts separate4 ,kolbe#dfh has described an additive compound with antipyrine1 ,zr7,,no71#f;,c,h,,on1 which is soluble in water1 and melts at #bag-bah4 #dfh ,zeitsch4 anorg4 ,chem4 #aiac1 #hc1 #adc4 ,when phosphoric acid or a soluble phosphate is added to a solution of a zirconium salt1 zirconium phosphates of doubtful composition are thrown down2 by fusion methods1 various double phosphates have been prepared4 ,a hypophosphate1 ,zr7,,po71,h,o1 has recently been obtained by ,hauser and ,herzfeld#dfi by precipitation4 ,the same authors have prepared a hypophosphite1 which is sensitive to light4 ,when hypophosphorous acid1 ,h,,po1 is added to a solution of zirconium nitrate1 a precipitate is obtained1 which dissolves in excess of the acid2 by addition of alcohol to the clear solution1 the hypophosphite1 ,zr7,h,,po71,h,o1 is thrown down in colourless1 highly refracting prisms1 which on exposure to sunlight for a short time become deep violet1 without further perceptible change4 #dfi ,zeitsch4 anorg4 ,chem4 #aiac1 #hd1 #ib4 ,zirconium carbonate has recently been obtained by ,chauvenet4#dgj ,addition of sodium carbonate precipitates a basic orthocarbonate1 ,zr,c,o1,zr,o1#h;,h,o1 soluble in excess2 when dried in vacuo1 the precipitate loses water1 forming the dihydrate1 ,zr,c,o1,zr,o1#b;,h,o4 ,when the latter compound is treated with carbon dioxide at a pressure of #cj-dj atmospheres1 the neutral orthocarbonate1 ,zr,c,o1#b;,h,o1 is formed4 ,when the compounds are heated1 other basic salts are obtained4 #dgj ,bull4 ,soc4 ,chim4 #aiac iv41 #ac1 #ded4 ,zirconyl oxalate1 ,zr,o1,c,o1 is obtained in the hydrated form when oxalic acid is added to a zirconium salt in the presence of hydrochloric or acetic acid4 ,it is a white powder1 soluble in oxalic acid1 and easily hydrolysed by water4 ,if an aqueous solution of oxalic acid be saturated with zirconium hydroxide1 an acid oxalate1 ,zr,o,h7,,hc,o71#g;,h,o1 is obtained on evaporation4 ,double oxalates are readily obtained by dissolving zirconium hydroxide in solutions of alkali hydrogen oxalates1 the general form being ,zr7,c,o,r71x,h,o4 ,the tartrate precipitated when tartaric acid is added to a zirconium salt in solution probably has the cyclic structure1 ,c,o,o,zr7,,oh7 ,,ch--,o ,zr7,,oh7 _/ ,,ch--,o ,c,o,o,zr7,,oh7 as shown by the great rise in the specific rotatory power of solutions of alkali oxalates on addition of zirconium compounds4 ,the precipitate dissolves readily in alkalies1 and various double alkali tartrates have been prepared2 the potassium salt1 ,zr,o7,c,h,o,k71#c;,h,o1 is analogous to the thorium alkali tartrates4 ,the solubility in alkalies is of great importance for the separation of iron and zirconium4 ,atomic ,weight of ,zirconium4--,the value of this constant is not very accurately known4 ,the ,international ,committee has adopted the value #ijf1 but there is some uncertainty as to the value of the decimal fraction4 ,berzelius in #ahbe employed the analytical sulphate method1 and found ,zr #hhdg4 ,the numbers of ,hermann 7#ahdd71 obtained by the analysis of the oxychloride1 #b,zr,o,cl1#i;,h,o1#dga were very discordant1 the mean giving the value #hief4 ,marignac in #ahfj analysed the potassium salt1 ,k,zr,f2 this he heated with strong sulphuric acid1 the residue being ignited until all the zirconium sulphate was transformed to oxide2 the weighed mixture was then freed from potassium sulphate1 and the residual oxide dried and weighed4 ,from the three ratios ,k,zr,f 3 ,zr,o1 ,k,zr,f 3 ,h,,so1 and ,k,,so 3 ,zr,o1 he obtained the mean values #ijjb1 #iaee1 and #ijfh respectively4 ,weibull in #ahha-ahhb determined the ratios ,zr7,,so7 3 ,zr,o and ,zr7,se,o7 3 ,zr,o by ignition of the sulphate and selenate respectively2 he obtained the values #hiee and #ijha4 #dga ,chauvenet 7loc4 cit47 could not confirm the existence of this hydrate4 ,bailey carried out a series of analytical sulphate determinations in #ahij1 obtaining the mean value #ijfef4 ,brauner criticises the method on the ground that the preparation of the pure neutral anhydrous sulphate is almost impossible2 the sulphate heated to #djj is not yet anhydrous1 so that ,bailey's result1 on this ground1 is probably too low4 ,venable in #ahih analysed the oxychloride2 he claimed to have obtained the compound ,zr,o,cl1#c;,h,o1 by heating the crystallised salt at #ajj-abe in hydrogen chloride1 a method which ,chauvenet 7loc4 cit47 has found to lead to the dihydrate1 ,zr,o,cl1#b;,h,o4 ,his value was #ijhjc4 ,detection and ,estimation4--,the following reactions may be employed to distinguish zirconium3 7#a7 ,the oxalate precipitated from neutral or faintly acid solution dissolves readily in excess of oxalic acid2 the oxalates of thorium and of the rare earth elements are practically insoluble under these conditions4 ,the fluoride also dissolves in excess of hydrofluoric acid or of alkali fluoride1 behaviour characteristic of this element alone among the group4 7#b7 ,by fusion with sodium carbonate in the oxidising flame1 a bead is obtained1 which1 when dissolved in boiling hydrochloric acid1 forms a solution which gives a voluminous precipitate on addition of disodium hydrogen phosphate1 if zirconium is present4 ,iron1 aluminium1 titanium1 thorium1 and rare earths have no influence on the test4#dgb #dgb ,biltz and ,mecklenburg1 ,zeitsch4 angew4 ,chem4 #aiab1 #be1 #baaj4 7#c7 ,a solution of a zirconium salt in hydrochloric acid gives an orange colouration with curcuma paper4 ,ferric and titanium salts1 if present1 must be reduced by means of zinc before the test is applied4 ,the estimation of zirconium is complicated by the difficulty of separating it from the accompanying elements4 ,the solubility of the oxalate in oxalic acid allows of a rapid and easy separation from thorium and rare earth elements1 so that iron1 aluminium1 and chromium only remain to be removed4 ,iron may be separated by the thiosulphate method1 or other processes mentioned on p4 #cch2 when free from that element1 zirconium may be separated from aluminium and chromium by precipitation with alkali iodate in presence of the least possible excess of acid4 ,the precipitates in the thiosulphate and iodate methods may be washed1 and ignited directly to the dioxide1 which is weighed as such2 if the zirconium is left after separation in solution1 it may be precipitated with ammonia1#dgc and after washing and drying1 ignited and weighed as dioxide4 #dgc ,on account of the adsorption of alkalies by the zirconium oxide gel1 potash or soda is never used for this precipitation4 ,thorium1 ,th #bcbd ,the name ,thoria 7thorina7 was proposed by ,berzelius in #ahag for what appeared to be a new earth1 but which in #ahbd was recognised as a basic yttria phosphate4 ,in #ahbh a new mineral was discovered by ,esmark near ,brevig in ,norway2 to the oxide isolated from this1 ,berzelius gave the name thoria1 from its resemblance to the substance he had obtained in #ahag4 ,the homogeneity of the new element was questioned by ,bergmann in #aheg1 and also by ,bahr in #ahfb1 but the conclusions of those authors have been shown to be quite unfounded4 ,thorium occurs in traces in a large number of common minerals1 and in varying quantities in most of the uranium and rare earth minerals4 ,its occurrence in monazite1 and the distribution of the latter mineral1 have already been dealt with2 the commercial treatment of monazite is described in ,chapter ,,xviii4 ,the oxide forms the chief constituent in ,thorite1 with its gem-variety ,orangite1 and the various secondary minerals1 and in the mineral ,thorianite1 in which the only other important constituent is uranous oxide4 ,the extraction from these minerals is a comparatively simple matter4 ,decomposition is easily effected by hydrochloric or sulphuric acid1 thorianite dissolving easily also in nitric acid2 the solutions obtained1 after appropriate treatment to remove silica1 excess of acid1 etc41 are treated with sulphuretted hydrogen1 to remove lead1 bismuth1 and similar foreign metals1 and freed from the rare earths by the carbonate1 oxalate1 or sulphate methods4 ,the last depends on the fact that thorium sulphate and its hydrates are much less soluble than corresponding compounds of the rare earth elements2 the first two on the fact that thorium salts dissolve readily in excess of alkali carbonates or oxalates1 whilst the rare earth compounds are much less easily soluble4 ,thorium1 like zirconium1 forms only one series of salts1 in which the metal is tetravalent4 ,the formula ,th,o was originally put forward by ,berzelius for the oxide1 from its resemblance to the ceria and yttria oxides1 and its general occurrence with these4 ,the true formula was deduced1 when the valency of zirconium had been decided by the vapour density experiments of ,troost and ,deville1 in #aheg1 from the isomorphism of zircon and thorite1 and the close relationship between the compounds of the two elements1 especially among the double fluorides1 and was confirmed by a determination of the specific heat of the metal by ,nilson in #ahhc4 ,in its chemical relations1 the element resembles zirconium1 though1 as is to be expected from the high atomic weight1 it shows a much more marked electropositive character1 approaching in this respect the elements of the yttrium group4 ,the oxide has no longer acid properties1 and the neutral salts1 though they hydrolyse readily and are therefore acid to indicators in solution1 may be recrystallised unchanged from aqueous solution4 ,the tendency to form double salts is still present1 though diminished2 the oxalate is soluble in a large excess of alkali oxalate1 but not in oxalic acid1 and the double fluorides are less numerous and varied than those of zirconium and titanium4 ,on the other hand1 it forms a well-crystallised and characteristic series of double nitrates1 ,r,th7,,no71 isomorphous with the analogous ceric salts4 ,in the behaviour of its sulphate it differs markedly from zirconium1 and closely approaches the rare earth elements4 ,the hydroxide has the characteristic tendency to form colloidal solutions and gels4 ,thorium is peculiar1 among the elements which have been considered1 through its property of giving characteristic radiations1 and disintegrating with formation of a whole family of new elements2 or1 as it is commonly expressed1 through its radioactive properties4#dgd ,the element has a half-life period of the order of #d #aj years2 in the course of decay1 it gives rise to mesothorium #a1 which is rayless1 but decays to mesothorium #b1 with its product radiothorium1 both of which give powerful radiations4 ,mesothorium #a of course occurs in all thorium-containing minerals1 and may be separated from monazite by addition of a barium compound during the sulphuric acid decomposition2 in consequence of the powerful radiating properties of its products1 it is itself of considerable importance1 and proposals for extracting it from monazite in the preparation of the thorium nitrate of commerce have been put forward 7see p4 #bgf74 #dgd ,the nature of the present work allows only the briefest reference to be made to the exceedingly interesting phenomena which centre about this subject2 for a more complete account1 the student should consult ,soddy1 ,the ,chemistry of the ,radio-,elements1 ,part ,i1 #aiaa4 ,mesothorium appears to be chemically identical with radium2 since monazite1 like all other thorium-bearing minerals1 contains uranium and radium1 the latter element is separated with the mesothorium1 and indeed1 having a very much larger half-life period1 constitutes by far the greater part of such #8mesothorium' preparations4 ,on account of the great activity of the mesothorium products1 the best preparations from monazite1 though estimated to contain only #a per cent4 of mesothorium to #ii per cent4 radium1 are said to be four times as active as pure radium compounds4 ,the chemical identity of the two products seems to preclude any possibility of determining the physical properties and constants of mesothorium4 ,the element radiothorium1 which was discovered by ,hahn in #aije1 in the mineral thorianite1 is chemically identical with the parent element thorium1 but can be separated by means of the intermediate element1 mesothorium #a4 ,the latter is readily separated by the sulphate precipitation1 and the radiothorium to which it gives rise may be separated by precipitation with ammonia4 ,thorium is also chemically identical with ionium1 the parent of radium1 and the thorium nitrate of commerce therefore contains important quantities of ionium--important that is1 in view of the high radiating power of the latter element4 ,the study of these relationships constitutes one of the most important and interesting fields in the province of radioactivity4 ,the ,metal4--,elementary thorium has not yet been obtained in the pure state1 owing to the ease with which it forms compounds and alloys with all the common elements1 and to its great affinity for oxygen2 the high melting-point also increases the difficulty of obtaining the pure metal4 ,berzelius attempted to reduce the alkali double fluorides and double chlorides with sodium or potassium2 ,nilson carried out the same reaction in a closed iron cylinder1 but his product still contained #bj per cent4 of thoria4 ,reduction of the oxide with magnesium is never complete1 and the carbon method gives only a mixture of carbide and metal4 ,electrolytic methods give no better results1 since the metal liberated at the cathode always encloses oxide and other impurities4 ,moissan and ,hnigschmid in #aijf1 by heating the carefully purified anhydrous chloride with sodium in a sealed glass tube from which air and moisture had been removed1 claim to have obtained a product containing only #c per cent4 of the oxide4 ,the element has recently been prepared in leaf form by forcing the amorphous product into the bore of a copper tube1 hammering into sheets1 and removing the copper by dilute nitric acid4#dge #dge v4 ,bolton1 ,zeitsch4 ,elektrochem4 #aijh1 #ad1 #gfh4 ,the amorphous impure metal is a dark grey powder1 of specific gravity #aac2 the hammered and strongly heated leaf has the density #abaf4 ,it burns readily in air with great brilliance1 and when finely powdered ignites if crushed or rubbed4 ,when heated in the electric furnace1 it melts1 according to von ,bolton1#dgf at about #adej2 von ,wartenburg#dgg found the melting-point to be about #agjj2 the fused beads resemble platinum in physical properties4 ,it is somewhat resistant to acids1 dissolving easily only in aqua regia1 and more slowly in fuming hydrochloric acid4 ,it combines directly when heated in sulphur or halogens1 and in nitrogen and hydrogen4 #dgf v4 ,bolton1 ,zeitsch4 ,elektrochem4 #aijh1 #ad1 #gfh4 #dgg ,ibid4 #aiji1 #ae1 #hff4 ,the hydride1 ,th,h1 is best obtained by heating the metal in hydrogen1 an energetic reaction taking place at a red heat4 ,winkler observed that a mixture of the dioxide with magnesium absorbs hydrogen readily when heated4 ,the hydride is a stable greyish-black powder1 not attacked by water1 but dissolving readily in hydrochloric acid1 with evolution of hydrogen4 ,the nitride1 ,th,n1 is prepared by heating the metal in the gas1 or the carbide in a stream of ammonia4 ,it is a brown powder1 decomposed by water with evolution of ammonia and formation of the dioxide4 ,the azide has been used for purposes of detection and estimation1 since in boiling solution it is hydrolysed with separation of the hydroxide2 zirconium and ceric salts also show this reaction1 but the rare earth salts give no precipitate4 ,the hydroxide1 ,th7,,oh71x,h,o1 is precipitated from solutions of thorium salts by alkalies or ammonia1 as a gelatinous white precipitate1 insoluble in excess4 ,it dissolves readily in mineral acids or in alkali carbonates4 ,hydrogen peroxide and ammonia throw down an hydrated peroxide1 ,th,o2 from neutral solutions hydrogen peroxide alone throws down peroxy-salts1 which contain acid groups4 ,this peroxide may also be obtained by the action of sodium hypochlorite or hydrogen peroxide on the hydroxide1 as in the case of the zirconium compound4 ,it readily gives up oxygen1 passing into the more stable peroxide1 ,th,o4 ,since in neutral or faintly acid solutions zirconium and the rare earths give no precipitate with hydrogen peroxide1 the reaction is extremely useful in the detection and estimation of thorium4 ,thorium dioxide1 ,th,o1 is obtained by the ignition of the hydroxide or of suitable salts as a white powder1 of which the properties and appearance depend largely on the method and temperature used in its formation4 ,whilst the residue obtained by ignition of the nitrate is an extraordinarily voluminous and light flaky mass1 the sulphate yields a dense thick powder2 the nitrate was therefore always preferred in the manufacture of incandescent mantles 7q4v471 as it was thought that the oxide obtained from it was the most suitable for illumination4 ,in the crystalline form the oxide has been obtained in the laboratory by fusion with borax and with potassium phosphate4 ,the first method gives tetragonal crystals1 probably isomorphous with those of rutile and cassiterite2 the phosphate fusion is said to give cubic crystals 7see p4 #gd74 ,the oxide is insoluble in acids1 but can be transformed into the sulphate by evaporation with concentrated sulphuric acid1 or fusion with alkali bisulphate4 ,it does not liberate carbon dioxide when fused with alkali carbonates4 ,by repeated evaporation with small quantities of acids1 thoria can be transformed into a gel soluble in water 7thorium meta-oxide74 ,the sol is an opalescent fluid1 orange-red by transmitted light1 and contains small quantities of the acid employed4 ,the hydroxide may also be obtained in this form by carefully washing it1 and boiling with small quantities of acids1 or with thorium or other salts1 or even by long continued washing with pure water2 similarly1 continued dialysis of thorium salts eventually yields such gels4 ,the colloid is positively charged1 and resembles the zirconium oxide gel in its relation to negatively charged colloids4 ,the gel is easily precipitated by electrolytes4 ,ignited thorium oxide has found considerable application in recent years a catalyst in the preparation of ketones by the contact method of ,sabatier and ,senderens4#dgh ,by passing mixtures of the vapours of appropriate acids over the catalyst heated to the necessary temperature1 good yields of the required ketones are obtained4#dgi #dgh ,cf4 ,senderens1 ,ann4 ,chim4 ,phys4 #aiac viii41 #bh1 #adc4 #dgi ,cf4 ,pickard and ,kenyon1 ,trans4 ,chem4 ,soc4 #aiac1 #ajc1 #aibc4 ,the sulphide1 ,th,s1 is obtained1 together with the oxysulphide1 ,th,o,s1 according to ,duboin1#dhj by passing a current of sulphuretted hydrogen over a mixture of thorium chloride with excess of sodium chloride1 at a red heat4 ,the former forms large brown crystals1 from which the small orange-yellow crystals of the oxysulphide may be separated by means of a sieve2 the latter is purified by treatment with warm nitric acid1 which dissolves the sulphide very readily4 ,the oxysulphide is also obtained when the anhydrous sulphate is heated in sulphuretted hydrogen4#dha #dhj ,compt4 rend4 #aijh1 #adf1 #hae4 #dha ,hauser1 ,zeitsch4 anorg4 ,chem4 #aijg1 #ec1 #gd4 ,the carbide1 ,th,c1 is obtained by the action of carbon on the oxide in the electric furnace2 it is a yellow crystalline mass1 decomposed slowly by water1 energetically by dilute acids in the cold1 with evolution of a complex mixture of hydrogen and hydrocarbons1 in which many members of the paraffin1 olefine and acetylene series have been observed4#dhb ,hydrogen constitutes over #ej per cent4 of the mixture1 the next most important constituents being the acetylenic hydrocarbons1 followed by ethane4 #dhb ,lebeau and ,damiens1 ,compt4 rend4 #aiac1 #aef1 #aihg4 ,thorium fluoride1 ,th,f1 is obtained anhydrous by passing hydrogen fluoride over the anhydrous chloride or bromide at a temperature of #cej-djj4 ,the tetrahydrate1 ,th,f1#d;,h,o1 is precipitated by addition of hydrofluoric acid to a solution of a thorium salt1 or by the action of the acid on the hydroxide4 ,hydrofluosilicic acid also throws down the fluoride1 even in the cold1 from solutions of thorium salts4 ,the fluoride is insoluble in water and mineral acids1 as well as in excess of precipitant2 this behaviour allows of a complete and easy separation of thorium from titanium and zirconium4 ,the rare earth fluorides are also much more easily soluble in concentrated mineral acids than thorium fluoride1 so that this compound may also be used in the separation from the rare earths4 ,when heated in a stream of the acid to #hjj1 the hydrated salt yields the oxyfluoride1 ,th,o,f2 ignited in the air1 it leaves the dioxide4 ,precipitation with potassium fluoride gives the double fluoride1 ,k,th,f1,h,o1 which may be obtained anhydrous by fusion of the mixed fluorides2 it is insoluble4 ,an amorphous insoluble compound1 ,k,th,f1#d;,h,o1 is obtained by boiling the hydroxide with a mixture of potassium hydrogen fluoride and hydrofluoric acid4 ,sodium and ammonium fluorides throw down the simple fluoride4 ,thorium chloride1 ,th,cl1 is obtained in the anhydrous form by all the usual methods1 the most convenient being perhaps the action of chlorine and sulphur monochloride on the heated dioxide4 ,it almost invariably contains small quantities of oxychloride4 ,when pure1 it forms colourless needles fairly stable in dry air2 the impure product gradually darkens in colour4 ,it dissolves in water with considerable evolution of heat1 and is soluble also in alcohol and moist ether4 ,it melts at about #hbj1 and sublimes unchanged at somewhat higher temperatures2 the vapour begins to dissociate at about #ajej1 the dissociation increasing rapidly as the temperature rises4 ,it resembles zirconium chloride in the ease with which it forms additive compounds with ammonia and organic bases1 and addition and condensation products with organic oxygen-compounds2 many double and complex chlorides are also known1 among which the platinum compounds ,th,pt,cl1#ab;,h,o and ,th,pt,cl1#bd;,h,o1 and the pyridine salt 7,c,h,,nh7,th,cl may be mentioned4 ,from aqueous solution the octohydrate1 ,th,cl1#h;,h,o1 separates at ordinary temperatures2 a heptahydrate and an enneahydrate have been described as precipitated from the alcoholic solution by addition of water4 ,the basic salts1 ,th7,,oh7,cl1#g;,h,o and ,th7,,oh7,cl1#e;,h,o1 have been obtained by addition of the hydroxide to alcoholic hydrogen chloride4 ,the oxychloride1 ,th,o,cl1 may be obtained by the carefully regulated action of carbon tetrachloride on the dioxide1 according to the equation3 ,th,o ,c,cl ,th,o,cl ,c,o,cl ,it is a colourless crystalline solid1 which takes up moisture from the air1 forming the hexahydrate4 ,thorium bromide1 ,th,br1 is a volatile solid which boils at #gbe2 it closely resembles the chloride4 ,the iodide and a basic iodide1 ,th7,,oh7,i1#aj;,h,o1 are known4 ,no cyanide of thorium is known1 addition of potassium cyanide merely causing separation of the hydroxide4 ,a ferrocyanide1 ,th,fe7,,cn71#d;,h,o1 is thrown down as a white powder by potassium ferrocyanide2 with potassium ferricyanide no precipitate is obtained4 ,the platinocyanide1 ,th,pt7,,cn71#af;,h,o1 is obtained by double decomposition in yellowish-brown prisms4 ,among the halogen oxysalts1 the perchlorate1 chlorate1 bromate1 and iodate were prepared by ,cleve4 ,the iodate is of great importance for purposes of detection and estimation1 from the fact that1 in presence of a large excess of alkali iodate1 it is insoluble in strong nitric acid1 whilst the analogous compounds of the rare earth elements dissolve readily in that solvent4 ,the sulphate1 ,th7,,so71 is obtained anhydrous by evaporating the excess of acid from a solution of the dioxide in oil of vitriol1 or by heating the hydrates4 ,it resembles the sulphates of the rare earth elements1 in that it dissolves in water at #j to form a highly supersaturated solution1 from which the hydrated forms separate out almost quantitatively when the temperature is allowed to rise4 ,the solubility relations of the various hydrates1 on account of their commercial importance1 are somewhat fully treated in ,chapter ,,xviii4 ,a dihydrate1 ,th7,,so71#b;,h,o1 is obtained by keeping the tetrahydrate at #aaj4 ,the ennea- and octohydrates are isomorphous with the corresponding thorium selenate hydrates1 and the ennea- and tetrahydrates with the analogous uranous sulphate hydrates4 ,the hydrates yield the anhydrous salt when heated to #djj2 the anhydrous sulphate has already a considerable dissociation tension 7#ae mm47 at #ege4 ,by treatment with excess of acid1 and subsequent heating to #acj in vacuo1 the acid sulphate1 ,th7,,so71,h,,so1 is obtained4 ,an insoluble basic salt1 ,th,o,s,o1#b;,h,o1 is formed by continued boiling of the tetrahydrate in dilute solution1 or more quickly by heating the solution in a closed tube to #abj-abe2 a monohydrate1 ,th,o,s,o1,h,o1 is also known4 ,halla#dhc has recently obtained the hydrate1 ,th,o,s,o1#e;,h,o1 by boiling a solution of the neutral sulphate with magnesium sulphate1 and also by treating the anhydrous sulphate with a little water in presence of magnesium carbonate4 #dhc ,zeitsch4 anorg4 ,chem4 #aiab1 #gi1 #bfj4 ,by precipitation with potassium sulphate the double salt1 ,th7,,so71#b,k,,so1#b;,h,o1 is formed2 this is soluble in water but insoluble in potassium sulphate solution4 ,the analogous sodium and ammonium salts are soluble both in water and excess of the corresponding alkali sulphate4 ,the sulphite1 ,th7,,so71,h,o1 is obtained as a white amorphous precipitate by warming a solution of a thorium salt with sulphurous acid4 ,basic sulphites and double sulphites are also known2 the precipitates obtained by addition of alkali sulphite dissolve readily in excess4 ,the hydroxide is almost insoluble in sulphurous acid1 behaviour which distinguishes thorium 7and zirconium7 from all the trivalent metals4 ,no thiosulphate is known1 the hydroxide being thrown down from boiling solution by addition of sodium thiosulphate3 this method of precipitation was formerly much used for purposes of estimation1 but it is more tedious and less accurate than the modern methods4 ,thorium nitrate1 ,th7,,no71#ab;,h,o1 crystallises at ordinary temperatures in large hygroscopic tablets1 very soluble in water and alcohol4 ,the hydrates1 ,th7,,no71#f;,h,o and ,th7,,no71#e;,h,o1 have been obtained from hot solution and from nitric acid solution respectively4 ,thorium is employed in commerce almost entirely in the form of this salt1 which is dehydrated until it contains about #dh per cent4 ,th,o1 which approximates to the formula ,th7,,no71#d;,h,o2 the commercial product1 however1 is not a definite hydrate4 ,kolbe#dhd has described the additive product with antipyrine1 #b,th7,,no71#e;,c,h,,on1 which melts at #afh4 ,the extent to which thorium salts are hydrolysed in solution is very considerable1 as is evident from the fact that the nitrate may be titrated with standard potash in presence of phenolphthalein as indicator2 the solution first becomes alkaline to this reagent when #ce molecules of potash have been added for each molecule of thorium nitrate present4#dhe ,of the large number of double nitrates which have been prepared1 the general types ,r,th7,,no71 where ,r ,,nh1,k1,rb1,cs1 and ,r,th7,,no71#h;,h,o1 where ,r ,mg1,mn1,zn1,ni1,co1 are the most important4 #dhd ,zeitsch4 anorg4 ,chem4 #aiac1 #hc1 #adc4 #dhe ,halla1 loc4 cit4 ,thorium phosphates4--,the precipitates obtained by addition of phosphoric acid or alkali phosphates to solutions of thorium salts are gelatinous solids of doubtful composition2 they dissolve in mineral acids and in alkali carbonates1 and their behaviour is of great importance in the technical treatment of monazite4 ,various phosphates and double phosphates are obtained by fusion methods1 but none of these are important4 ,the phosphite1 ,th7,,hpo71#c;,h,o1 and hypophosphite1 ,th7,h,,po71 are insoluble solids obtained by double decomposition4 ,the hypophosphate ,th,p,o1#aa;,h,o1 is of great importance for purposes of detection and estimation1 since it is thrown down quantitatively from strongly acid solutions2 under these conditions the rare earths remain in solution4 ,no neutral carbonate of thorium is known4 ,alkali carbonates precipitate a basic salt1 which dissolves readily in excess2 this fact is of very great importance in the commercial extraction of thorium1 the sodium and ammonium double carbonates of the cerium elements being almost insoluble in alkali carbonates4 ,addition of alcohol to the solution throws down double carbonates1 which can be washed with ice water4 ,the salts ,k,th7,,co71#aj;,h,o1 ,na,th7,,co71#ab;,h,o1 and 7,,nh7,th7,,co71#f;,h,o have been obtained in this way2 they dissolve readily in water or dilute alkali carbonate1 though on warming or diluting the solution1 the hydroxide separates4 ,the thallium compound1 ,tl,th7,,co71 is sparingly soluble1 and is thrown down from a solution of the ammonium compound on addition of a thallium salt2 it has been proposed for the microchemical detection of thorium4 ,the quantitative separation of thorium by means of pure moist lead carbonate has been proposed for the purpose of estimation 7see p4 #bhh74 ,thorium oxalate1 ,th7,c,o71#f;,h,o1 is precipitated quantitatively by means of oxalic acid1 even in presence of considerable quantities of mineral acids4 ,it is less soluble in sulphuric acid than any of the rare earth oxalates1#dhf and is not attacked1 as are the latter compounds1 by concentrated nitric acid4 ,in hydrochloric acid the solubility first increases rapidly with the concentration of the acid1 and then suddenly decreases2 this behaviour is due to the formation of an oxalochloride1 #c,th7,c,o71,th,cl1#bj;,h,o4 ,when the amorphous oxalate obtained by precipitation is allowed to remain for a considerable time in contact with acids1 it forms characteristic tetragonal prisms of the more stable form4 ,the dihydrate1 ,th7,c,o71#b;,h,o1 is obtained when the hexahydrate is dried over sulphuric acid1 or heated to #ajj4 ,the salt dissolves easily in excess of alkali oxalate1 but is precipitated from the solutions by mineral acids1 a fact which allows of another means of separation from zirconium1 the double oxalates of which are much more stable towards acids4 ,the solubility of the oxalate in alkali oxalate allows of separation from the rare earth elements1 whilst its insolubility in excess of oxalic acid can be used for the separation from zirconium4 #dhf ,hauser and ,wirth1 ,zeitsch4 anorg4 ,chem4 #aiab1 #gh1 #ge4 ,the formate and acetate can be obtained in the form of neutral salts by the action of the acids on the hydroxide2 by double decomposition1 amorphous precipitates of basic salts are obtained4 ,with tartaric acid stable complex compounds are formed1 as shown by the fact that alkalies will not precipitate the hydroxide from a solution in presence of that reagent1 and by the elevation of the specific rotatory power4 ,many complex salts are known1 the simplest having the composition ,th,o7,c,h,o,r71#h;,h,o1 where ,r ,k1,na1,,nh2 these are obtained by dissolving thorium hydroxide in concentrated solutions of alkali hydrogen tartrates4 ,thorium acetylacetone1 ,th7,c,h,o71 is precipitated by addition of ammonia to an aqueous solution of the nitrate mixed with acetylacetone dissolved in ammonia2 the solid is recrystallised from alcohol1 and melts at #aga4 ,atomic ,weight of ,thorium4--,the value adopted by the ,international ,committee 7#aiad7 is #bcbd1 but most of the determinations carried out within the last thirty years show considerable discrepancies4 ,the earlier work of ,berzelius 7#ahbi7 and ,chydenius 7#ahfa7 led to very widely varying results1 and for the same reason little reliance can be placed on the results of ,delafontaine 7#ahfc7 and ,hermann 7#ahfd74 ,in #ahgd ,cleve determined the constant by ignition of the sulphate1 obtaining the mean values #bcdjc and #bccig2 the figure #bcd based on these results was for many years accepted as the true atomic weight4 ,a series of determinations carried out by ,nilson in #ahhb led to much lower results4 ,he employed the sulphate ennea- and octohydrates1 first dehydrating these1 and then igniting to oxide1 and showed that ,cleve's value must be too high on account chiefly of the hygroscopic nature of the ignited oxide1 which increases in weight when kept2 but his own values show considerable discrepancies4 ,the ratio ,th7,,so71#i;,h,o-,th,o 3 ,th,o 7enneahydrate converted to oxide7 gave the figure 7corrected to vacuo7 #bcbea1 whilst the ratio ,th,o 3 #b,,so 7anhydrous sulphate to oxide7 gave #bcbaf2 the ratio ,th7,,so7 3 #i;,h,o 7hydrate to anhydrous salt7 gave1 however1 #bccge4 ,the value obtained for the ratio ,th,o 3 #b,,so for anhydrous sulphate prepared from the octohydrate was #bcbdi 7corrected to vacuo74 ,five years later1 ,krss and ,nilson prepared the anhydrous sulphate from the pure octohydrate1 and ignited this to the oxide4 ,the ratio ,th,o 3 #b,,so gave as a mean of very concordant results the figure #bcbdi4 ,brauner criticises these values on the ground that no details are given as to the temperature required to obtain the anhydrous salt from the hydrates1 and that probably some traces of sulphate must be decomposed at the temperatures required 7#dej-ejj7 to drive off all the water4 ,the results obtained from the enneahydrate are to a great extent invalidated by the doubts as to the purity of the hydrate1 completeness of dehydration1 etc41 which arise from the discrepancies in the values deduced from the three ratios4 ,he accepts1 however1 the figure #bcbdi obtained by ,nilson and by ,krss and ,nilson from material separated as octohydrate1 with some uncertainty as to the second decimal figure4 ,brauner himself employed the oxalate method in #ahih2 the purified hexahydrate was used1 the percentage of thoria being determined by ignition1 and of 7,c,o7 by titration with permanganate4 ,the ratio ,th,o 3 #b;,c,o gave results varying from #bcbba to #bcbbi1 but as the value rose continuously as purification was carried further and further1 he did not feel justified in taking a mean value4 ,in #aijj ,urbain determined the constant with material purified by the acetylacetone method4 ,he prepared the octohydrate1 heated it for ten hours in a bath of sulphur vapour at #ddj1 and ignited the anhydrous salt so obtained at a white heat4 ,the ratio ,th,o 3 #b,,so gave the result 7corrected to vacuo7 ,th #bccfg4 ,brauner criticises the value on the ground that the hydrated salt was heated in a vessel open to the air1 and that at the high temperature obtained1 traces of moisture gaining access to the sulphate caused hydrolysis1 with loss of sulphuric acid2 this would cause the results to be too high4 ,in #aije ,meyer and ,gumperz employed the same method1 and obtained values varying from #bcbb to #bcbg1 with the mean #bcbdg4 ,finally ,brauner carried out an extended investigation to disprove the heterogeneity of thorium which had been #8discovered' by ,baskerville 7#aijd71 in the course of which he showed the atomic weight of the element to lie between the limits #bcbcd and #bcbeb4 ,detection of ,thorium4--,the element is best detected in a mixture of earths by the following reactions3 7#a7 ,precipitation with hydrogen peroxide from warm1 faintly acid solution4 7#b7 ,precipitation with sodium hypophosphate1 ,na,h,p,o1 in concentrated hydrochloric acid solution4 ,on boiling1 a perceptible precipitate is obtained if only traces of thorium are present2 but ceric and zirconium salts and titanium must be absent4 ,the latter element gives no precipitate under these conditions if hydrogen peroxide is present2 ceric salts may be decomposed by boiling4 ,the possible presence of zirconium renders it necessary to boil the hypophosphate precipitate with nitric acid2 on addition of oxalic acid to the clear solution1 thorium is precipitated1 whilst zirconium remains in solution1 and may be detected4 7#c7 ,potassium azide1 ,,kn1 throws down thorium hydroxide from boiling neutral or faintly acid solutions4 ,ceric salts if present must be previously reduced2 zirconium must be previously removed by oxalic acid4 7#d7 ,precipitation may be effected with potassium iodate in strong nitric acid solution4 ,here also ceric salts must be reduced before applying the test4 ,zirconium also gives the test2 the precipitate must therefore be washed and warmed with oxalic acid1 in which thorium iodate is insoluble1 whilst zirconium iodate is soluble4 ,the methods of estimating thorium are given in ,chapter ,,xviii4 ,,part ,,iii ,,the ,,technology ,,of ,,the ,,elements ,,chapter ,,xvii ,,the ,,incandescent ,,mantle ,,industry--,,historical ,,and ,,general ,,introduction ,the group of elements which we are considering can be divided1 from the point of view of technical application1 into two classes4 ,the first of these contains one element only1 titanium1 which in its technology1 as in its chemistry1 stands apart from the others2 it will1 accordingly1 be treated in a separate chapter4 ,the second class contains the yttrium and cerium metals1 with zirconium and thorium2 the technical importance of these elements is due chiefly to the use of their oxides in illumination1 to a small extent in ,nernst lamps1 and to a much greater extent in the so-called ,incandescent ,lighting4 ,the manufacture of incandescent mantles#dhg is a large and ever-extending industry1 intimately bound up with the older process of coal-distillation1 with its innumerable ramifications2 indeed1 it may be said that but for the ingenious invention of ,dr4 ,auer1 illumination by means of coal-gas would to-day have been almost obsolete4 ,the discovery which resulted in the production of the familiar incandescent mantle of the present day may be regarded as the culmination of a century's effort to increase the value of coal-gas as an illuminating agent4 ,in the present chapter it is proposed to outline the history of these endeavours1 and to give a short general account of ,auer's work and its results4 #dhg ,the term #8incandescent mantle' is not1 perhaps1 scientifically very desirable4 ,it is used here1 not only on account of its general acceptance1 but also because there seems to be no brief and convenient term which might be used in its stead4 ,soon after the introduction of gas as an illuminating agent it was realised that the luminosity of the flame is dependent on the presence of solid particles1 which by the heat of combustion of the gas are raised to a temperature at which they emit radiations of wave-lengths corresponding to the #8luminous rays' of the spectrum4 ,a non-luminous flame of sufficiently high temperature1 therefore1 can be rendered luminous by the introduction of suitable solids1 and numberless investigators have striven1 during the past century1 to discover the most suitable method of increasing the luminosity of a flame in this way4 ,the luminosity of the ordinary #8bats-wing' or #8flat' flame1 now so rapidly going out of use1 is due to the presence in the outer zone of the flame of heated particles of carbon1 produced by the decomposition--or partial combustion--of #8dense' hydrocarbons1 i4e4 of hydrocarbons having a high percentage of carbon4 ,ordinary coal-gas consists largely of a mixture of hydrogen and methane1 both of which burn with practically non-luminous flames1 with small quantities of olefines1 acetylenes1 etc41 to which the luminosity is chiefly due4 ,it would appear1 then1 that by the introduction of dense hydrocarbons1 a gas of poor illuminating power might be made much more valuable as a source of light4 ,on the other hand1 it is also apparent that the same end might be achieved by the introduction into a non-luminous or feebly luminous flame of an altogether foreign substance1 introduced as such1 and not continuously consumed1 as is the carbon in the former method4 ,both these directions of improvement have been followed2 since1 however1 the results achieved by the latter method have become recently of far greater importance1 the applications of the first method will be dismissed quite briefly1 and the history of the second will then be treated somewhat fully4 ,the first important attempt to increase the illuminating power of gases burning with feebly luminous flames was that of ,faraday1 who in the course of an investigation into the causes of the variations in luminosity of #8portable gas1' discovered benzene1 or bicarburet of hydrogen1 as he called it1 in #ahbf4 ,in #ahcj an engineer named ,dunnovan undertook to illuminate ,dublin by means of water-gas#dhh which he #8carburised' by addition of dense hydrocarbons4 ,during the latter half of the nineteenth century this method became of some importance4 ,it has been applied1 in particular1 to enrich the #8natural gas' of ,ohio1 ,north ,america4 ,the dense hydrocarbons necessary for this purpose are obtained by the process known as #8cracking4' ,the viscous residues from the distillation of the mineral oil of the district are allowed to drop into a brick chamber1 of which the walls are raised to a bright red heat1 and the dense hydrocarbons which are evolved are removed by a current of the gas to be enriched4 ,in this way a gas of relatively high illuminating power is obtained4 #dhh ,water-gas is a mixture of equal volumes of carbon monoxide and hydrogen1 obtained by blowing steam through a glowing coke furnace4 ,at intervals the steam is shut off1 and air is blown through to raise the temperature of the coke4 ,in the year previous to that in which ,faraday first carburised water-gas1 ,berzelius had observed that thoria and zirconia1 when heated in a non-luminous flame1 emit an intense white light4 ,similar behaviour had long before been observed in the cases of magnesia1 alumina1 lime1 zinc oxide1 etc4 ,the first practical application of this property of the oxides was that of ,drummond1 who in #ahbf heated a pencil of lime in the oxy-hydrogen flame and obtained the intense white light which has since become so familiar as the ,drummond or #8lime-light4' ,a further development in this direction was due to du ,motay and ,marchal1 who in #ahfg illuminated the ,place de ,tuileries and the ,htel de ,ville in ,paris by means of pencils of compressed zirconia--magnesia was also used--heated by means of oil vapour and oxygen4 ,the use of non-luminous flames to secure illumination1 by raising the temperature of solids suspended in them to the point of incandescence was proposed in #ahci by ,cruickshank1 who used a mantle of platinum wire1 covered with lime and rare earths1 which he heated by means of water-gas4 ,in #ahdf ,gillard employed mantles of platinum wire1 raised to incandescence in the flame of burning hydrogen1 which he obtained by passing steam over heated iron wire2 later he used water-gas 7#ahdh71 his lamps with this modification being employed in ,paris and in ,philadelphia4 ,narbonne was later illuminated 7#ahef-ahfe7 by a similar device1 but permanent success could hardly be obtained in view of the cost of the platinum mantles1 which lasted only a few months4 ,the same mantle was proposed in #ahhb by ,lewis1 the ordinary ,bunsen flame being suggested as the source of heat4 ,in the same year ,popp exhibited at the ,crystal ,palace lamps in which a platinum mantle was raised to incandescence by means of a flame of coal-gas and heated air4 ,these attempts1 however1 served only to show that no permanent advance could be made in this direction4 ,a new development was made in #ahhj by ,clamond4 ,he prepared a paste by grinding up calcined and powdered magnesia with a concentrated solution of magnesium acetate2 by forcing this through a press he obtained a ribbon which was then wound crosswise on a wooden shaper1 dried carefully1 and ignited4 ,in his later experiments twenty per cent4 of zirconia was added to the magnesia4 ,the mantle was supported in a platinum cage and heated in the flame of a mixture of coal-gas and heated air4 ,this mantle gave an intense light1 but was too fragile for extended use4 ,in the following year1 ,lundgren patented a process by which lime1 magnesia1 and zirconia1 made into a paste by the addition of gum1 were forced through a press1 and the resulting thread wound on a graphite-covered shaper4 ,the mantle so obtained was stable1 and gave an intense white light1 but after having been heated for some time the oxides crumbled to powder4 ,a modification of this process was introduced by ,knfler in #ahid1 in an attempt to use a cellulose solution containing rare earth salts2 this was forced through jets1 and the cellulose precipitated as a continuous thread from which the mantle was made4 ,a further modification of ,knfler's process by ,plaisetty in #aija was technically successful2 but these developments must be taken up in a later chapter 7vide p4 #cjg74 ,in #ahhc a process was patented by ,fahnehjelm in ,stockholm1 by which for the first time a cheap and stable mantle of considerable efficiency was produced1 and which1 but for the advent of the ,auer mantle1 would undoubtedly have been commercially successful4 ,fahnehjelm's mantle consisted of an arrangement of needles or lamell of magnesia1 lime1 zirconia1 etc41 suspended over a burner4 ,the plates and needles were usually arranged in the form of a comb of suitable shape1 and were found to give an intense light1 and to be long-lived4 ,in later forms the combs were made of rods of magnesia dipped into solutions of chromium salts4 ,the great disadvantage of this invention lay in the fact that the combs required to be heated in the flame of water-gas1 in order to secure a good incandescence2 had it been possible to attain a sufficiently high temperature by the use of coal-gas1 it is doubtful whether the ,auer mantle would have ever been evolved4 ,the more important attempts to secure arrangements by which the radiations of heated solids could be used for illumination have now been outlined and the ground cleared for the consideration of the work of ,baron von ,welsbach4 ,there remain yet to be mentioned1 however1 two attempts which are of especial interest in view of that work4 ,the first is that of ,frankenstein1 who in #ahdi made use of a #8,light-multiplier' obtained by impregnating gauze with a paste of chalk and magnesia ground with water4 ,the second is that of ,edison1 who proposed 7#ahgh7 to utilise the observations of ,bahr and ,bunsen 7#ahfd7 and of ,delafontaine 7#ahgd71 of the remarkable incandescence exhibited by the yttria and erbia earths1 and the terbia earths1 respectively1 when heated2 he suggested the employment of a mantle of platinum wire covered with zirconia and the oxides of the rare earth metals1 a proposal similar to that put forward nearly forty years earlier by ,cruickshank4 ,about the year #ahhj ,dr4 ,carl ,auer began the study of the rare earth elements4 ,the chemical aspect of his work has already been dealt with 7vide p4 #afh72 but the results obtained by the technical application of his observation that threads of cotton1 impregnated with a solution of salts of the elements1 leave after ignition a coherent ash of oxide1 which glows brightly when heated1 have been of far greater importance than the purely scientific aspect1 valuable though that is4 ,a series of experiments soon showed that a fabric of suitable shape1 impregnated with a solution of nitrates or acetates of the rare earth elements1 after being dried and drawn together at one end by means of a platinum wire1 can be ignited in a ,bunsen flame in such a way as to leave a coherent skeleton of the earth oxides1 which can be formed and hardened by suitable manipulation with a high temperature burner2 the mantle so prepared1 when suspended from a lateral support in a ,bunsen flame1 gives a light of considerable intensity1 the colour varying with the oxides employed from green to orange tints4 ,the earlier mantles1 which were placed on the market about #ahhc1 consisted chiefly of oxides of lanthanum and zirconium1 with smaller quantities of the other oxides1 selected according to the shade of light desired4 ,these mantles were protected by patents taken out in ,france in #ahhd1 and in ,germany in #ahhe and the following years4 ,the process#dhi was briefly the following3 ,a vegetable fibre1 of cylindrical form1 woven from threads of about #jbb mm4 diameter1 is washed with dilute hydrochloric acid1 then with distilled water1 and impregnated with a #cj per cent4 solution of the selected salts4 ,the fabric is then wrung out and dried1 and cut into suitable lengths1 allowance being made for subsequent shrinkage4 ,one end of each cylinder is then drawn together by means of a platinum wire1 and the mantle hung from a side support over a burner and incinerated4 ,the head is then treated with a solution of aluminium and magnesium nitrates 7beryllium nitrate and the corresponding phosphates are also specified7 to strengthen it1 and the mantle dried1 and #8formed' by means of a very hot flame4 ,this first patent protected several definite mixtures of salts1 chosen so that the mantle should emit light of a definite known tint4 ,the chief oxides employed were lanthana1 yttria1 magnesia1 and zirconia4 ,a ,german patent granted in #ahhfdij protects the use of thorium salts1 and a long list of salts of the elements with numerous acids2 an important advance mentioned in this specification is the process of collodinisation of the finished mantle1 by dipping in a solution of rubber in benzene or of collodion 7cellulose nitrate7 in ether and alcohol1 which renders the product strong enough for transport4 ,from #ahhe to #ahia numerous improvements were effected2 asbestos threads were substituted for platinum wire1 central rods of magnesia replaced the lateral platinum support1 and various mixtures of oxides were tried4 ,none of the innumerable mixtures employed1 however1 was successful in establishing the struggling industry on a firm basis in face of the vigorous competition of the electric lamp1 and it was not till #ahia that the introduction of the final #8,auer ,mixture1' which is in use at the present day1 gave the welcome assurance of a certain success to von ,welsbach and his assistants4 ,the discovery of this mixture was a result of the examination of a quantity of impure thoria2 it was found that mantles made from the nitrate gave a light which steadily decreased in intensity as the impurities were removed4 ,it needed only the observation that the impurities consisted chiefly of cerium compounds to turn the long and arduous investigation in the direction of final success1 and our present mantles1 which consist approximately of #ii per cent4 thoria and #a per cent4 ceria1 were placed on the market in #ahia1 the composition being announced by patent in #ahic4dia #dhi ,vide ,d4 ,r4 ,p4 #ciafb4 ,granted ,september #bc1 #ahhe4 #dij ,d4 ,r4 ,p4 #daide4 #dia ,vide1 e4g4 ,moeller1 ,e4 #abd1 #ahic4 ,the effect of increasing or decreasing the ratio of the two oxides1 and the theories which have been advanced to account for the results1 must be referred to in a later chapter 7vide p4 #bid74 ,it may be mentioned here1 however1 that practically no other known mixture gives such satisfactory results1 though mantles have been manufactured of alumina with small quantities of chromic oxide1 and #8inverted' mantles made of these oxides with zirconia have recently been advocated by ,professor ,lewes1#dib an authority on gas lighting4 ,mixtures of alumina and uranium oxide have also been patented1 but no mantles appear to have been manufactured according to the specifications4 ,in this connection1 also1 may be mentioned the various attempts to evade the ,auer patents by taking advantage of the #8discovery' of #8new' elements4 ,one enterprising firm1 after having an account of a #8new' element1 ,lucium1 inserted in a well-known scientific periodical1 put salts on the market1 and proceeded to manufacture mantles from what were proved by analysis to be cerium compounds4 ,similar #8new' elements were ,russium1 ,kosmium1 and ,neo-kosmium1 names which covered various mixtures of thorium and cerium compounds with other salts4 #dib ,vide ,d4 ,r4 ,p4 #bahccc of ,january #aiaj4 ,after the introduction in #ahia of the final ,auer mixture1 progress became rapid4 ,the original mantles1 made from cotton1 had many disadvantages2 thus after being in use for some time they were found to shrink considerably1 with marked decrease in strength and light-giving power4 ,once the success of the new form of lighting was assured1 numberless investigations were undertaken to lengthen the life and increase the efficiency of the mantles4 ,the most important of these were connected with the endeavour to replace cotton by some fabric which on ignition would leave the oxide skeleton in a harder1 more coherent and more elastic condition4 ,the first great advance in this connection was the introduction of ,ramie fibre by ,buhlmann in #ahih4 ,ramie1 ,china-grass1 or grass-cloth1 as it is sometimes termed1 is a fabric made from the fibres of the tschuma plant of the ,yang-tse-kiang valley and other parts of ,asia2 mantles made from it last longer and maintain their efficiency much better than the earlier cotton mantles1 which they have very largely displaced4 ,the use of artificial silk was patented by ,de ,mare in #ahid1 but his process was unworkable2 it was an effort to adapt to the purposes of incandescent lighting the nitro-cellulose process introduced by ,chardonnet in #ahij for the manufacture of artificial silk4 ,in #ahig ,de ,lery and in #aijj ,plaisetty made further efforts in this direction1 and finally in #aijb-aijc the latter worked out a process by which mantles were made directly from the spun fabric4 ,these mantles are superior in every way to the earlier ramie or cotton kinds1 and are rapidly coming into general use1 especially for lamps using high-pressure gas4 ,numberless patents for the manufacture and improvement of this kind of mantle have been taken out during the last ten years2 the most important of these will be dealt with in a later chapter4 ,attempts have been made to secure greater strength and toughness in mantles in other directions also4 ,the use of metallic wires in the fibre has been suggested2 numerous patents deal with mantles #8strengthened' by doubling the thread at intervals1 and by special methods of weaving the fibre4 ,one method1 which follows on the lines of ,glamond and ,lundgren1 proposes#dic the use of mantles made from various oxides mixed with silica1 the whole being worked into a paste by use of a gum or soap1 from which threads are prepared by pressure2 mantles made from these threads are said to be very strong and porous4 ,another patent#did protects the manufacture of #8incandescence bodies' made from plates or combs prepared from a thread obtained in a rather similar way4 ,a third of these innumerable suggestions recommends a preliminary impregnation of the fabric with an aluminium or magnesium salt1#die from which the oxide is precipitated on the fabric by a suitable means1 impregnation with the ordinary #8lighting fluid' being effected after drying4 ,quite an early patent#dif proposes the impregnation of the prepared mantle1 either after or just before burning off1 with an alcoholic solution of an organic silicon compound1 so that when the mantle is in use a skeleton of silica is formed to #8strengthen' the oxide ash4 ,no useful purpose can be served by extending the list of these proposals2 enough has been said to indicate the various directions in which so many vain attempts at improvement have been made4 #dic ,laigle1 ,d4 ,r4 ,p4 #bafhga of ,december1 #aiji2 see also ,d4 ,r4 ,p4 #bafhgg and #baifdj4 #did ,michaud and ,delasson1 ,d4 ,r4 ,p4 #bajfdj1 ,june1 #aiji2 see also ,d4 ,r4 ,p4 #bbgbeg4 #die ,zdanowich1 ,e4 #bggee1 #aijh4 #dif ,jasper1 ,e4 #cjade1 #ahig4 ,from the mechanical and physical side the recent developments have been very marked4 ,the introduction of the #8inverted' lamp was a tremendous step forward1 and paved the way to the second great improvement1 the use of #8high-pressure' gas1 with which such successful results are being obtained4 ,the form of lamp now coming into use for street lighting gives #aejj candle-power per mantle1 and usually carries three mantles2 each lamp thus develops #dejj candle-power4 ,the purely mechanical devices which are now used to secure #8automatic' lighting are rapidly bringing this form of lamp into favour for street illumination4 ,a full account of these developments would be entirely beyond the scope of the present work4 ,in the following chapters1 therefore1 no complete treatment of the incandescent lighting industry can be given2 but whilst the chemical aspect is treated at some length1 many points of more purely technical character1 which are connected with this1 have also been included4 ,,chapter ,,xviii ,,the ,,chemical ,,treatment ,,of ,,monazite ,it has been stated in the previous chapter that the first ,auer mantles were made of mixtures of various rare earth oxides1 the mixture of thoria with #a per cent4 of ceria being first employed in ,october1 #ahia4 ,the impetus given to the mantle industry by the success of the new mixture caused an immediate demand for thoria1 which was at that time extracted from thorite 7see p4 #dc74 ,a #8thorite-fever' broke out along the coasts of ,scandinavia1 and the price of orangite rose to #fjj marks per kilogram 7about #ac #ajs4 per pound avoirdupois71 sinking again shortly to #hj marks#dig 7about #a #afs4 per lb74 ,the discovery of the monazite sands of the ,carolinas and ,brazil1 which at the present rate of consumption may be considered to be1 for all practical purposes1 inexhaustible1 placed the industry on a firm basis1 and the pure monazite1 extracted from these deposits by the methods outlined in ,chapter ,,vii1 is now almost the sole source of the thorium nitrate of commerce4 ,small quantities are obtained from thorianite1 the separation of the pure material presenting1 in this case1 very little difficulty by reason of the solubility of the mineral in acids and the very high percentage of thoria4 #dig ,vide ,bhm1 #8,die ,thorium ,industrie1' ,chem4 ,ind4 #aijf1 #bi1 #dej and #dhh4 ,the extraction of pure thorium compounds from monazite is a process of very great technical difficulty4 ,the percentage of thoria is small1 whereas that of the ceria oxides is high4 ,the mineral is almost always decomposed by heating with concentrated sulphuric acid1 and when the resulting pasty mass is taken up with water1 a large amount of free sulphuric acid must be present in order to hold the rare earth phosphates in solution4 ,for the separation of thoria from ceria and yttria compounds in acid solution no processes were known until quite recently4 ,when it is remembered that the thorium nitrate used for the manufacture of mantles must be of a degree of purity which very few commercial products ever approach1 some idea of the difficulties of the extraction may be obtained4 ,decomposition of the ,monazite4--,two processes have been used for the working up of monazite4 ,the first of these consists in fusing the mineral with soda1 and extracting the sodium phosphate with water2 the earths may then be taken into solution with acid1 and the separation effected as outlined below4 ,this method is very rarely used4 ,a process has been proposed1 in which the monazite is fused with carbon in an electric furnace2 the cooled mass is treated with mineral acids1 which take the earths into solution free from phosphoric acid4 ,no technical application has so far been made of this proposal4 ,the method commonly used is that in which the sand is decomposed by means of sulphuric acid4 ,the charge usually employed1 about two to three hundred kilograms1 requires from four to six hours' heating1 about twice the weight of concentrated acid being needed4 ,the operation is carried out in cast-iron vessels1 and an efficient draught must be maintained to remove the acid fumes2 the factories are usually isolated4 ,the treatment with sulphuric acid converts the phosphates chiefly into sulphates2 when the reaction is finished1 the liquor fumes strongly and begins to thicken1 heating being stopped when a thick broth is obtained4 ,the cooled mass is extracted with water1 care being taken to maintain a degree of acidity sufficient to prevent any precipitation of the phosphates4 ,it has been already stated in ,part ,i 7vide p4 #gc7 that a strongly radioactive product4 ,radiothorium1 has been obtained from the mineral thorianite4 ,this body is produced by the atomic degradation of thorium1 and an intermediate body1 mesothorium1 has been found to be formed during the change4 ,mesothorium is a substance which1 though it appears to be chemically identical with radium1 has an activity equal to three hundred times that of radium1 and when in equilibrium with its degradation products the #8rays' it emits are very similar to those of the latter element4 ,since mesothorium is a degradation-product of thorium1 it occurs in minute quantities in all thorium minerals1 and by reason of the possibility of using it as a substitute for radium1 its extraction becomes a matter of importance4 ,soddy#dih has shown that if a barium compound be added to monazite before the treatment with sulphuric acid1 the mesothorium remains with the barium sulphate2 this is readily separated from the heavy unchanged grains of sand1 and is purified1 and finally obtained as chloride by treating the solution with hydrogen chloride4 ,on recrystallisation of the barium chloride1 the active products are concentrated in the less soluble part1 and it is possible to prepare on the commercial scale a mixture which1 though it contains only #jbe per cent4 of mesothorium1 has an activity equal to that of pure radium bromide4 ,this mixture contains #be per cent4 of radium compounds1 radium being present as an original constituent of monazite2 owing to the chemical identity of radium and mesothorium1#dih the latter cannot be separated1 but ,soddy1 by removal of much of the barium compound in the laboratory1 has obtained a product four times as active as the pure radium salt4 #dih ,proc4 ,chem4 ,soc4 #aiaj1 #bf1 #ccf1 and ,e4 #beejd1 ,november1 #aiaj4 ,see also ,hahn1 ,chem4 ,zeitg4 #aiaa1 #ce1 #hde4 ,it is probable that the treatment of monazite will in the future be modified by the addition of barium sulphate before the sulphuric acid decomposition1 to allow of the commercial extraction of its mesothorium4 ,separation of ,thorium4--,the separation of a crude thorium product from the acid solution obtained after decomposition of the mineral can be effected in two ways1 both of which are based on the fact that thoria is less basic than the oxides of the cerium and yttrium metals4 ,in the first1 the rare earth elements1 including thorium1 are precipitated as oxalates by the addition of oxalic acid to the acid solution4 ,these are again taken into solution by the action of hydrochloric acid on the hydroxides1 obtained by prolonged digestion of the oxalates with sodium hydroxide2 the acid solution is then treated carefully with sodium hydroxide1 or pure powdered magnesia1 until about one-sixth of the bases has been precipitated1 the liquid being constantly stirred4 ,thorium hydroxide being very weakly basic is precipitated before the other hydroxides1 and the precipitate obtained1 after one or two repetitions1 contains most of the thorium originally present in the monazite4 ,in the second process1 thorium is partially separated from the other metals by adding gradually to the solution obtained after the treatment of the mineral with sulphuric acid1 the quantity of magnesia calculated to precipitate a suitable fraction of the earths1 with constant stirring2 this throws down a mixture of phosphates containing almost all the thorium and some of the other elements4 ,the slimy phosphate precipitate is dissolved in hydrochloric acid1 and the earths precipitated as oxalates2 the precipitate must be washed thoroughly in order to remove phosphoric acid4 ,it will be seen that these two methods differ only in that in the first the phosphoric acid is removed before the precipitation of thorium1 whereas in the second the thorium is precipitated as phosphate1 and this transformed into oxalate4 ,quite recently1 methods have been proposed by which the thorium can be separated in a fairly pure condition from the acid solution obtained from the sulphuric acid treatment4 ,rosenheim1 ,meyer and ,koppel#dii protect the use of hydrofluosilicic acid 7,h,si,f71 and its salts1 for this purpose4 ,the sodium salt1 added to the hot acid liquid1 produces a quantitative separation of thorium silicofluoride2 the precipitate is washed by decantation1 and treated with sulphuric acid1 the thorium sulphate being then purified directly by the sulphate method described below4 ,a second method proposes to make use of the insolubility of thorium hypophosphate1 ,th,p,o1#aa;,h,o1 which was found by ,kaufmann in #ahii to be insoluble in water1 and in acids and alkalies4 ,this method has already been in use for some years for analytical work2#ejj it appears to be readily susceptible of adaptation for the technical extraction1#eja the sodium hypophosphate1 ,na,h,p,o1#f;,h,o required as the precipitating agent being obtainable in large quantities by the electrolytic oxidation of copper phosphide1 employed as the anode in an electrolytic cell4#ejb ,this method also gives a thorium compound sufficiently free from other earths to be subjected at once to the refining process2 the hypophosphate has in fact been suggested as a very suitable compound for the impregnation of artificial silk mantles directly4 ,the thorium nitrate of commerce1 however1 is still prepared almost entirely from the crude product obtained by one or other of the two methods of fractional precipitation first described1 so that it becomes necessary to outline the method generally employed for separating from this a compound pure enough to be suitable for the final refining process4 #dii ,d4 ,r4 ,p4 #badhhf1 ,october1 #aiji4 #ejj ,rosenheim1 ,chem4 ,zeitg4 #aiab1 #cf1 #hba2 also ,koss1 ibid4 #fhf #eja ,wirth1 ,zeitsch4 angew4 ,chem4 #aiab1 #be1 #afgh4 #ejb ,rosenheim and ,pinsker1 ,ber4 #aiaj1 #dc1 #bjjc4 ,the crude oxalate or hydroxide is thoroughly digested with a concentrated solution of sodium carbonate4 ,the carbonates of the cerium elements are much less soluble in sodium carbonate solution than is thorium carbonate4 ,after thorough digestion the liquid is filtered from the undissolved carbonates4 ,the thorium is reprecipitated from the filtrate1 either as oxalate1 by the addition of hydrochloric acid 7if the crude material was in the form of oxalate71 or as hydroxide1 by the addition of sodium hydroxide4 ,the process is again repeated1 and a final digestion is then made with ammonium carbonate2 addition of an alkali to the clear filtrate now gives thorium hydroxide sufficiently pure to be used for the last refining4 ,purification of the ,thorium ,compounds4--,the object of this last stage is to remove from the thorium compound small quantities of cerium and yttrium salts which cannot be separated by the carbonate method4 ,the chief process is the sulphate crystallisation1 the principles underlying which have been thoroughly examined in the patient researches of ,koppel and ,holtkamp4#ejc ,since the process is based on the solubilities of the various thorium sulphate hydrates1 it is necessary to consider these in some detail4 #ejc ,zeitsch4 anorg4 ,chem4 #aiaj1 #fg1 #bff4 ,the solubility-curve of thorium sulphate was examined by ,demaray and by ,roozeboom4 ,three important hydrates are known1 viz4 ,th7,,so71#i;,h,o1 ,th7,,so71#h;,h,o1 and ,th7,,so71#d;,h,o1 other unstable intermediate compounds being said to exist4 ,from a study of the diagram it will be seen that the hydrate with #h molecules of water is labile1 whilst the #i-;hydrate and the #d-;hydrate have a transition temperature at #dc;,c41 the transition temperature of the #h-;hydrate and the #d-;hydrate being just below this4 ,illustration3 ,,fig4 #aj ,since the #h-;hydrate is labile with regard to the #i-;hydrate1 and the transition temperatures are so near1 the former will be formed first as a solution cools1 and by reason of the great similarity of the solubility-curves for the #i- and #h-;hydrates the rate of change of this to the #i-;hydrate will be very slow4 ,in practice1 therefore1 it is always the #h-;hydrate which is formed1 and it is on the separation of this compound that the success of the process depends4 ,the anhydro-compound1 ,th7,,so71 which can be obtained by heating any of the hydrates to #cjj-djj;,c41 is very soluble at #j1 but slowly hydrates itself and separates from the solution as the #h-;hydrate1 which has a very low solubility4 ,the sulphates of the cerium metals1 compounds of which form the chief impurities to be removed1 are considerably more soluble1 and can be separated by repeated crystallisations4 ,the thorium hydroxide to be purified is dissolved in sulphuric acid1 and in the first form in which the method was employed1 the thorium sulphate obtained by evaporation of the solvent was heated until it became anhydrous4 ,this was dissolved to saturation at #j1 and the solution raised to the boiling-point1 the #d-;hydrate being precipitated2 this treatment was repeated several times4 ,it was pointed out by ,bunsen1 from theoretical grounds1 that this method could never yield a pure thorium salt1 and ,krss and ,nilson accordingly introduced a modification4 ,the impure sulphate1 after dehydration1 as before1 is dissolved at #j1 and allowed to come to ordinary room temperature1 #bj2 the hydrate which separates 7the #h-;hydrate7 is collected and dried at high temperature and the crystallisation repeated4 ,this method gives a fairly pure salt after three recrystallisations1 but the process is very tedious1 owing to the time required for drying and heating the hydrate4 ,for this reason the method was further modified by ,cleve and ,witt4 ,the crude sulphate is boiled with ammonia1 and the hydroxide obtained dissolved in hydrochloric acid2 addition of sulphuric acid to the concentrated solution in the cold transforms the chloride into the sulphate1 which separates as the #h-;hydrate at ordinary temperatures4 ,three repetitions give a satisfactory product1 and in this form the method is now much used4 ,the work of ,koppel and ,holtkamp referred to above has placed the process on a sound basis4 ,these authors have examined the solubilities of the various hydrates in presence of hydrochloric1 nitric1 and sulphuric acids1 and mixtures of these1 at different temperatures4 ,they find that hydrochloric acid is to be preferred to nitric acid1 in the process of ,cleve and ,witt1 as besides its lower price1 its use involves less loss than that of the latter acid2 excess of hydrochloric acid is not harmful within wide limits1 whilst a slight excess of sulphuric acid over the quantity required to form the sulphate is desirable1 to secure the greatest yield4 ,finally1 the temperature at the addition of the sulphuric acid must not be allowed to rise above #be1 for in the presence of so much acid the transition temperature to the #d-;hydrate1 normally #db1 is considerably lowered2 it is necessary to avoid separation of the #d-;hydrate1 which is a flocculent unworkable precipitate4 ,recently it has been proposed to carry out the purification by use of alkyl hydrogen sulphates1#ejd as it is stated that the differences of solubilities of the alkyl sulphates of thorium and the cerium metals are greater than in the case of the sulphates themselves4 ,it is also claimed that the presence of a small quantity of the alkyl sulphate in the thorium nitrate which forms the final product has a good effect on the quality of the mantles made from it4 #ejd ,kreidl u4 ,heller1 ,d4 ,r4 ,p4 #bccjbc1 ,march1 #aiaa2 ,f4 #daddfc1 ,june1 #aiaj4 ,another process of purification which has found considerable commercial application is the acetate crystallisation1 thorium acetate being considerably less soluble than the acetates of the cerium elements4 ,the impure hydroxide is dissolved in acetic acid and the solution evaporated to dryness2 repeated washing with small quantities of water removes the cerium acetates1 and a fairly pure salt is obtained4 ,this is repeatedly damped with nitric acid and heated to dryness1 but even after this treatment a certain amount of unchanged thorium acetate is usually present4 ,in a second form of this method1 due to ,haber1 the impure hydroxide is dissolved in hydrochloric acid1 and the acetate precipitated by addition of sodium acetate4 ,the precipitate is filtered off and re-dissolved in acid1 and the acetate again thrown down by means of sodium acetate4 ,the precipitate is then dissolved in nitric acid1 and the solution evaporated to dryness4 ,in this form the method gives very good results1 even from a comparatively crude product2 but the process is1 of course1 considerably more expensive than the sulphate purification4 ,the high price of the necessary reagents1 again1 is a bar to the technical application of the very simple and efficient process of ,wyrouboff and ,verneuil4 ,these authors suggest the precipitation of thorium peroxide from a warm dilute neutral solution by means of hydrogen peroxide1 a process which is quantitative and yields a very pure product4 ,the last traces of the cerium metals can be completely removed by a second precipitation4 ,the cost of hydrogen peroxide is too high1 however1 to allow its employment on such a large scale1 and the method has not1 in consequence1 come into general use4 ,the thorium nitrate obtained after purification by the sulphate method1 or by the less generally employed acetate method1 is usually considered sufficiently pure for technical purposes4 ,even now1 however1 it may contain traces of sulphate1 of iron1 of alkalies1 and of cerium metals4 ,if absolute purity is desired1 the salt may be dissolved1 and freed from all impurities1 except the cerium compounds1 by precipitation with ammonium oxalate and thorough washing2 the oxalate may then be dissolved in chromic acid1 and potassium chromate solution added drop by drop2 the precipitated thorium chromate is nearly free from other rare earth compounds1 and repetition of the process will give a pure salt4 ,the separation from cerium metals may also be effected by the hydrogen peroxide process4 ,if the technical processes are carefully carried out1 however1 a thorium nitrate of a very high degree of purity may be obtained1 and the laboratory purification need only be undertaken if material is needed for very accurate quantitative work4 ,preparation of ,thorium ,nitrate from ,mantle-ash4--,since the ordinary incandescent mantle1 in use1 consists only of the pure thoria and ceria1 with small quantities of alumina1 lime1 and magnesia1 which have been employed to strengthen the #8head1' the working-up of mantle-ash gives an easy means of obtaining the nitrates1 and high prices are accordingly paid for the ash in quantity4 ,at one period of great competition between rival manufacturers1 canvassers went from house to house in many large towns buying up mantle residues1 to be used for the extraction of the thorium for #8lighting-fluid4' ,for this purpose1 the oxides are treated with hot concentrated sulphuric acid1 the cooled residue dissolved in water1 and the thorium and cerium precipitated free from compounds of aluminium1 magnesium1 and calcium by oxalic acid4 ,if pure thorium nitrate1 free from cerium1 is required1 the oxalates are added to the last precipitate from the double carbonate purification in the treatment of monazite 7vide supra71 and the ordinary processes of refinement continued2 more often1 however1 the mixed nitrate for impregnation of the mantle-fabric is required1 and this is obtained by ignition of the oxalates and solution of the oxides so obtained in nitric acid1 more cerium nitrate being added if necessary4 ,extraction of ,cerium ,nitrate4--,since monazite is primarily a phosphate of the cerium metals1 the percentage of thoria being usually quite low 7vide ,monazite1 ,chapter ,,vi71 very large quantities of compounds of the cerium group of elements are annually produced in the process of extraction of thorium4 ,there is at present a very limited demand for these compounds 7vide ,chapter ,,xxi71 no important uses having yet been found for them4 ,in the ordinary process of extraction of the thorium1 these elements remain as the sparingly soluble double carbonates1 whilst the thorium double carbonate is removed in solution4 ,from the mixed salts which contain #ej-fj per cent4 of the cerium compound1 the cerium nitrate required for the manufacture of mantles is prepared1 but the amount so used is a small fraction of the whole1 and large quantities of compounds of cerium and the allied elements are available as soon as profitable uses can be found4 ,three processes are in general use for the preparation of cerium nitrate from the mixed carbonates2 all of these are based on the fact that cerium can become tetravalent1 forming in this condition compounds which can readily be separated from those of the allied elements1 which can be obtained only in the trivalent condition4 ,when ceria is dissolved in hot nitric acid1 ceric nitrate1 ,ce7,,no71 is formed1 though the action of nitric acid on cerous carbonate or oxalate gives rise to cerous nitrate4 ,two of the three processes are based on this reaction1 and for these the mixed carbonates are dissolved in hydrochloric acid1 freed from foreign elements by precipitation with oxalic acid1 and the oxalates ignited to the oxides1 which are then dissolved in the required quantity of nitric acid4 ,in the first process the cerium is precipitated from this solution by merely pouring it into a large excess of very dilute nitric acid1 when a yellow basic ceric nitrate is precipitated2 this is washed with dilute nitric acid by decantation1 dissolved in concentrated acid1 and purified by a second precipitation in the same way4 ,in the second process1 separation is effected by addition to the nitric acid solution of the calculated quantity of ammonium nitrate2 the solution is concentrated to incipient crystallisation1 and on cooling the double ceric ammonium nitrate1 ,ce7,,no71#b,,nh,,no1 separates4 ,this is collected1 washed with dilute nitric acid1 and recrystallised until a pure salt is obtained4 ,the double nitrate can be readily decomposed by ignition1 leaving ceria1 which is dissolved in nitric acid2 the nitrate is obtained by evaporation4 ,the third method1 due to ,drossbach1 is based on the oxidation of cerium salts in neutral solution by potassium permanganate4 ,the mixed carbonates are dissolved in hydrochloric acid1 a further quantity of the carbonates stirred in1 to neutralise excess of acid1 and a solution of the required quantity of potassium permanganate added4 ,the reaction is said to proceed according to the equation3 #c;,ce,o #b,k,mn,o ,h,o #f;,ce,o #b,,koh #b,mn,o ,the precipitated solid is separated1 and dissolved in acid2 the cerium is then precipitated as the oxalate1 which is transformed into nitrate in the usual way4 ,the solution contains the other elements of the cerium group1 which are precipitated by means of sodium hydroxide4 ,the yield obtained by this method is very good1 practically the whole of the cerium being separated without loss2 whilst it has the further advantage that the remaining elements of the group can be precipitated at once after the separation4 ,analysis of a ,monazite or ,monazite ,sand for ,thorium4--,since the commercial value of a monazite sand or concentrate1 or of the pure mineral1 depends1 at present1 entirely on the percentage of thoria1 it is important to have a rapid and reliable method of estimating this constituent4 ,the only reliable methods of quantitatively decomposing the mineral1 however1 all involve acid treatment1 and excess of acid must always be present to prevent precipitation of phosphates4 ,until recently1 no way was known for estimating thorium in an acid solution1 and all the earlier methods therefore involved tedious processes for complete removal of phosphoric acid1 so that the salts could be obtained in neutral solution4 ,this was usually effected by precipitation of the whole rare earth content with oxalic acid1 and thorough washing of the oxalates2 these can then be dissolved directly in fuming nitric acid on the water-bath1 or ignited to the oxides1 which may then be dissolved in the same reagent4 ,the solution of nitrates is evaporated to dryness1 to effect removal of the excess of acid1 the nitrates dissolved in water1 and the thorium estimated in the neutral solution4 ,among the earliest methods employed for the estimation in neutral solution was the thiosulphate precipitation4#eje ,thorium thiosulphate is not known2 when sodium thiosulphate is added to a neutral solution of a thorium salt1 a precipitate of thoria mixed with sulphur is obtained1 by hydrolysis of the potential thiosulphate1 and decomposition of the unstable thiosulphuric acid4 ,the method1 however1 leaves much to be desired2 other earths are partly precipitated1 and the separation of thoria is not complete4 ,for analytical purposes the precipitate obtained is redissolved in hydrochloric acid1 and a second precipitation with thiosulphate effected4 ,the filtrates from the two precipitations are collected1 and the whole earth-content precipitated from these with ammonia2 the hydroxides are dissolved in hydrochloric acid1 and again treated with thiosulphate to throw down any thoria which has escaped the previous precipitations4 ,the three precipitates of thoria are then collected1 dried1 and ignited for weighing as pure thorium dioxide1 ,th,o4 #eje ,full accounts of this and the two following methods will be found in an important paper by ,benz1 ,zeitsch4 angew4 ,chem4 #aijb1 #ae1 #big ,even more tedious and unsatisfactory is the method based on the solubility of thorium oxalate in excess of ammonium oxalate in neutral solution4 ,the solution is boiled1 ammonium oxalate added1 and after some moments a small quantity of ammonium acetate solution4 ,on cooling1 the oxalates of the cerium metals separate1 and can be collected2 thoria is precipitated from the filtrate by addition of ammonia4 ,the process must be repeated two or three times1 the solution being allowed to stand for one or two days each time1 and finally the thoria must be precipitated by thiosulphate to remove traces of the other bases before it can be weighed4 ,benz 7loc4 cit47 gives a complete account of this method1 and quotes numerous analyses carried out to test its accuracy4 ,far more satisfactory than either of the above is the peroxide method used by de ,boisbaudran and ,cleve1 and later by ,wyrouboff and ,verneuil4#ejf ,thorium is completely precipitated as a #8peroxide salt' 7,th,o1,,so or ,th,o1,n,o respectively7 from warm neutral solutions of the sulphate or nitrate on addition of dilute hydrogen peroxide1 a second precipitation being necessary to free it from cerium compounds4 ,wyrouboff and ,verneuil state that the process is rendered difficult by the fact that the peroxide cannot be converted into the dioxide by heating1 either alone or with acids1 as decrepitation takes place and may cause loss2 they accordingly reduce the compound in presence of hydrochloric acid by ammonium iodide1 and precipitate thorium hydroxide by ammonia4 ,benz 7loc4 cit47 does not find this difficulty2 he states that small quantities of the peroxide dissolve easily in acids without loss1 and further finds that if an ammonium salt be added to the neutral solution of the thorium compound before addition of hydrogen peroxide1 the precipitate forms much more readily and is very easily handled4 ,borelli#ejg states that the precipitated peroxide can be ignited without loss to the dioxide1 and weighed as this4 #ejf ,compt4 rend4 #ahih1 #abf1 #cdj4 #ejg ,abstract in ,j4 ,soc4 ,chem4 ,ind4 #aiji1 #bh1 #fbe4 99 99 99 99 99 ,the azoimide method of ,dennis#ejh is of interest rather than of use4 ,he finds that addition of potassium azoimide1 ,n,k1 precipitates thoria quantitatively from a neutral solution1 the reaction being expressed by the equation3 ,th7,,no7 #d,n,k #b;,h,o #d,,kno ,th,o #d,n,h ,cerium1 however1 if present1 is always precipitated with the thorium1 and cannot be removed by re-precipitation2 this fact1 together with the cost of the reagent and the difficulty of obtaining it pure1 renders the method quite useless for mineral analysis4 #ejh ,zeitsch4 anorg4 ,chem4 #ahig1 #ac1 #dab4 ,numberless experiments have been made with organic acids in the hope that an easy method of separation might be found1 but though some useful results have been obtained1 precipitation has always to be effected in neutral solution1 so that all such processes involve the tedious preliminary work of which an outline has been given above4 ,metzger#eji finds that a quantitative separation of thorium can be effected from a solution in #dj per cent4 alcohol by use of fumaric acid2 a second precipitation is needed to secure the complete removal of the cerium elements4 ,neish#eaj uses meta-nitrobenzoic acid1 which precipitates the thorium salt from a boiling solution2 cerium earths1 if present1 are carried down in small quantities1 and are removed by dissolving the precipitate in dilute nitric acid1 adding a further quantity of the organic acid1 and treating carefully with ammonia to almost complete neutralisation4 ,the compound obtained by this second precipitation is the pure thorium salt4 ,more recently1 ,smith and ,james#eaa have shown that sebacic acid gives a quantitative precipitation of the thorium salt1 from boiling neutral solution1 as a voluminous granular precipitate1 readily filtered and washed2 sebacic acid is very sparingly soluble in cold water1 but dissolves readily at #ajj1 and since1 in virtue of this property1 it can be readily recovered after use1 the authors suggest it as a suitable reagent for the technical separation of thorium from monazite4 ,in all cases where thorium is precipitated as an organic salt in quantitative analysis1 the precipitate is dried and ignited1 and the residue weighed as the pure dioxide4 #eji ,j4 ,amer4 ,chem4 ,soc4 #aijb1 #bd1 #bge and #ija4 #eaj ,ibid4 #aijd1 #bf1 #ghj4 #eaa ,ibid4 #aiab1 #cd1 #bha4 ,an interesting method has been worked out by ,giles4#eab ,if pure moist lead carbonate be stirred into a neutral solution of rare earth compounds1 thoria is completely precipitated4 ,only the tetravalent elements are separated by this method1 so that if ceric compounds are present1 they must first be reduced by means of sulphuretted hydrogen or sulphur dioxide2 zirconium1 if present1 must afterwards be separated from the thorium4 ,one precipitation is said to ensure almost complete separation from the trivalent elements4 ,the precipitate is collected1 washed1 and dissolved in hydrochloric acid2 after filtering1 if necessary1 the solution is saturated with sulphuretted hydrogen1 to ensure complete removal of the lead1 and thorium hydroxide is then precipitated by ammonia4 ,the drawback to this method lies probably in the fact that it is necessary to use absolutely pure lead carbonate1 a substance which1 as the author's elaborate process of purification seems to show1 could not be obtained very cheaply on a large scale4 #eab ,chem4 ,news1 #aije1 #ib1 #a and #cj4 ,an account has recently been published#eac of a volumetric method for the estimation of thorium4 ,the mixed oxides are dissolved in concentrated acetic acid1 and the solution titrated with a standard solution of ammonium molybdate4 ,this reagent effects complete precipitation of thorium1 but does not react with compounds of the cerium elements2 excess of the molybdate is shown by a solution of diphenyl carbazide1 ,,co7,,nh,,nh,c,h71 used as an external indicator4 ,the carbazide1 which is obtained by the action of phenyl hydrazine on urea1 has the property of producing definite1 though evanescent1 colourations with compounds of many of the metallic elements2 a drop of the working solution1 brought into contact with a drop of the carbazide solution1 shows a deep rose colouration when excess of ammonium molybdate is present4#ead #eac ,metzger and ,zons1 ,j4 ,ind4 ,eng4 ,chem4 #aiab1 #d1 #dic4 #ead ,vide ,skinner and ,ruhemann1 ,trans4 ,chem4 ,soc4 #ahhh1 #ec1 #eed2 also ,cazeneuve1 ,compt4 rend4 #aijj1 #aca1 #cdf4 ,the iodate process of ,meyer and ,speter#eae has the great advantage that it is carried out in a strongly acid solution1 so that here the tedious purification from phosphoric acid is no longer necessary4 ,after decomposition of the mineral with sulphuric acid1 the sulphates are extracted with water1 and a suitable quantity of nitric acid added2 the solution is then treated with a nitric acid solution of potassium iodate1 and the thorium iodate which separates is dissolved in concentrated nitric acid1 and re-precipitated to remove traces of the cerium elements4 ,the iodate1 after washing1 is dissolved in hydrochloric acid1 and reduced by sulphur dioxide2 the hydroxide is then precipitated by ammonia4 ,since zirconium is also thrown down under these conditions1 the hydroxide is dissolved in hydrochloric acid2 pure thorium oxalate is precipitated from this solution by oxalic acid1 and is ignited and weighed as oxide1 in the usual manner4 ,since ceric iodate is also insoluble in dilute nitric acid1 it is necessary to reduce any ceric compound which may be present before the iodate treatment by the usual methods4 #eae ,chem4 ,zeitg4 #aiaj1 #cd1 #cjf4 ,see also ,zeitsch4 anorg4 ,chem4 #aiaa1 #ga1 #fe4 ,another method which can be carried out in acid solution is based on the insolubility of the hypophosphite1 ,th,p,o1#aa;,h,o1 in dilute acids4#eaf ,to the boiling acid solution1 an aqueous solution of sodium hypophosphate1 ,na,h,p,o1#f;,h,o1 is added drop by drop4 ,the precipitate1 which contains any titanium and zirconium present in the original solution1 is best treated with a mixture of sulphuric and fuming nitric acids2 the phosphates produced by the oxidation are freed from nitric acid by evaporation1 dissolved in water1 with addition of sulphuric acid1 and thorium precipitated as the oxalate1 which is then ignited as usual4 ,this method has been suggested for the technical separation of thorium from monazite 7vide p4 #bgh74 ,since the precipitations by means of sodium hypophosphate and potassium iodate can be carried out with solutions obtained directly from the product of the action of sulphuric acid on the mineral1 these two methods are probably more suitable for the rapid and accurate estimation of thorium for technical purposes than any of the others mentioned4 #eaf ,wirth1 ,zeitsch4 angew4 ,chem4 #aiab1 #be1 #afgh2 see also ,koss1 ,chem4 ,zeitg4 #aiab1 #cf1 #fhf1 and ,rosenheim1 ibid4 p4 #hba4 ,,chapter ,,xix ,,the ,,manufacture ,,of ,,mantles ,,from ,,cotton ,,and ,,ramie ,the fabric chosen for the manufacture of the original ,welsbach mantles was a specially selected cotton1 woven from threads of a specified thickness4 ,the oxide skeleton left after burning off the impregnated fabric1 however1 showed many serious defects4 ,gradual shrinkage occurred during use1 so that the mantle was gradually withdrawn from the hottest zone of the flame2 the contraction also resulted in crumpling1 which caused the fragile fabric to fall to pieces4 ,the light-giving power showed a gradual but continuous diminution1 so that after a hundred hours1 the decrease sometimes amounted to thirty per cent4 of the original intensity4 ,lastly1 owing to the fragility due to the torsion introduced by the twisting together of so many short fibres in the spinning of the fabric1 the life of these mantles was very short1 and their susceptibility to shock very great4 ,with the introduction of ramie1 many of these defects disappeared4 ,mantles made from this fibre do not shrink continuously1 nor to any considerable extent1 so that crumpling does not occur2 the decrease in light-giving power is very much less than with the cotton mantles1 the life is much longer1 and the resistance to shock very much greater4 ,microscopic examination of the fibres1 and of the ash left after burning off1 shows that these differences are traceable to differences in the mechanical structure of the two fabrics4 ,the cotton thread is spun from a very large number of very short fibres1 which are twisted together1 whereas the separate fibres of ramie are of much greater length1 and the torsion in the thread correspondingly less4 ,in the case of artificial silk1 continuous filaments are spun into threads1 and this simple fact accounts for the very much greater durability and elasticity of mantles made from this fabric4 ,the introduction of ramie for the manufacture of mantles effected no great alterations in the processes employed in the case of cotton2 the treatment of artificial silk1 however1 requires a profoundly modified method1 and in consequence the preparation of this fabric and the manufacture of mantles from it1 are considered separately in another chapter4 ,though the manufacture of artificial silk was first commenced in ,france1 it is in ,germany that its adaptation to the incandescent mantle industry has been successfully effected4 ,its adoption1 however1 has not yet become general1 and by far the greatest number of mantles are to-day made from ramie4 ,in the ,united ,states1 where the early working of the monazite deposits gave a great impetus to the industry1 the manufacturers still cling largely to the older methods1 so that even now quite a considerable number of mantles are made from cotton4 ,in the present chapter1 a short account will be given of the methods employed in the manufacture of mantles from ramie and cotton4 ,the general methods of preparation of cotton fabrics are well known4 ,ramie is prepared from the tschuma plant1 which is found in ,india1 ,china1 and other parts of ,asia4 ,the fibre is obtained from the inner side of the bark2 this is dried1 pressed into bales1 and exported4 ,after removal of gum and resin1 by heating with sodium hydroxide solution under pressure1 the fibre is bleached1 dried and cleaned1 and then combed and spun in the usual manner4#eag #eag ,for the preparation and technical uses of ,ramie1 or ,rhea1 as it was formerly called1 vide ,cross1 #8,the ,industrial ,uses of ,cellulose1' in the ,cantor ,lectures of the ,society of ,arts1 #ahig1 vi1 p4 #bj4 ,washing4--,the influence of even small quantities of impurities on the intensity of the light emitted by a mantle is remarkably great1 and the manufacture requires a degree of care and attention far beyond that needed in ordinary technical processes4 ,washing of the fabric in particular must be very thorough and careful1 if a mantle of reasonable quality is required4 ,if the mineral content of the fabric1 i4e4 the ash left on incineration1 amount to more than #jjc per cent4 of the total weight1 the quality of the mantle is seriously affected4 ,particularly is this the case if even the smallest traces of iron come in contact with the fabric2 on this account wooden implements must be used as far as possible in the washing house1 and all iron parts must be carefully protected so that no water can drip from them on to the material4 ,the fabric is used in the form of a long cylindrical tube usually of about twice the diameter required for the base of the finished mantle4 ,before the mineral impurities can be removed1 this must be entirely freed from grease4 ,it is therefore washed thoroughly with a warm solution of sodium carbonate1 which removes all the hydrolysable fats4 ,if paraffin or other non-hydrolysable grease is present1 the alkaline wash must be followed by a soap wash4 ,the fabric is now cleansed from alkali and soap by running water1 and mineral impurities are removed by treatment with dilute hydrochloric acid 7#a-c per cent47 at a temperature of #ej-fj;,c42 it is finally washed free from acid with distilled water4 ,so susceptible is the mantle to traces of impurity that the use of ordinary tap water1 or even of a distilled water which has become contaminated to the smallest degree1 for this final washing1 will considerably lower its efficiency4 ,a centrifugal machine removes most of the water1 and the drying is completed by passage over wooden rollers1 through a small chamber1 of which the air is kept at #cj-dj;,c4 ,the dried fabric is now cut into lengths ready for the next process4 ,illustration3 ,,fig4 #aa ,impregnation4--,the composition of the #8,lighting ,fluid1' as the solution of salts used for impregnation is technically termed1 varies slightly according to the nature of the mantle required1 and the conditions of washing4 ,it is of the greatest importance that the ratio of thoria to ceria should be constant and definite2 the usual proportions are chosen so that the ratio of the oxides is #ii 3 #a4 ,fig4 #aa shows at a glance to what a remarkable extent small variations in the percentage of ceria affect the luminosity of the finished product4#eah ,the thorium nitrate is made up with distilled water to a solution of #be-ce per cent4 strength1 and the calculated quantity of a standard solution of cerium nitrate is added4 ,it is usual to add to the mixture a small quantity of another nitrate1 which on ignition will leave an oxide of which the function is to strengthen the skeleton of ash4 ,beryllium1 zirconium1 magnesium1 or aluminium nitrate is usually employed1 in quantity calculated to leave an amount of oxide constituting about #je per cent4 of the total oxides2 for ramie fabrics1 beryllium nitrate is generally chosen4 #eah ,numberless theories have been advanced to account for the extraordinarily high light-emitting power of this particular mixture of thoria and ceria4 ,an account of these would be beyond the province of the present work2 the reader who desires to pursue the subject should consult the interesting work of ,dr4 ,h4 ,w4 ,fischer1 ,der ,auerstrumpf1 ,ahren's ,sammlung1 #aijf1 vol4 xi4 ,vide also ,lvy1 ,l'clairage l'incandescence par le gaz1 ,paris1 #aiaj1 ,ch4 ,,ii2 and ,foix1 ,thse prsente la ,facult des ,sciences de ,paris1 ,paris1 ,gauthier-,villars1 #aiaj4 ,the diagram is after ,drossbach1 ,j4 ,gasbel4 #ahih1 #ceb4 ,after having been immersed for two to five minutes in the solution1 the separate lengths are freed from excess of the lighting fluid by means of a small wringing machine4 ,the pressure between the rollers must be regulated very exactly1 since on the amount of solution taken up by the fabric will depend the mass of the oxide skeleton4 ,the weight of oxides left after ignition should be #je-jf gm4 for a #8normal' upright mantle of #ie cm4 length1 corresponding to #aj-ab gms4 of the nitrates1 or1 for a #cj per cent4 solution1 to #cc-dj gms4 of solution4 ,the weight of the fabric before impregnation is approximately #e gms4 for cotton1 #c gms4 for ramie1 and #ae gms4 for artificial silk4 ,a cotton mantle-fabric1 therefore1 must be allowed to retain rather less1 a ramie fabric rather more1 than its own weight of solution1 whilst an artificial silk fabric must take up #b-b times its own weight of the fluid4 ,the weight of the oxide ash left from these quantities has been found by experience to be most suitable2 if the mass is greater than this1 the light-emission is diminished without a compensating gain in strength2 if it is less1 the light-emission is indeed greater1 but the mantle becomes too fragile4 ,the impregnated fabric-lengths1 after passing through the wringing machine1 are drawn singly on to glass forms which are arranged on stands1 and freed from moisture in a drying room by hot air1 a temperature of about #cj;,c4 being maintained4 ,three to four hours are required1 under these conditions2 if the drying be too rapid1 considerable shrinkage occurs1 and the mantles obtained are then extremely fragile4 ,the ,mantle ,head4--,the normal upright mantle is supported from a central rod of compressed magnesia--fused quartz has recently been suggested#eai--;by means of an asbestos thread4 ,the thread in the older patterns was supported by simply doubling over the fabric at the end which was to become the head2 more generally1 however1 a strip of tulle or gauze is sewn to the head end before the impregnation4 ,in order to strengthen the head1 it is treated before #8finishing' with a hardening or #8fixing' fluid1 which usually consists of a mixture of magnesium and aluminium nitrates in aqueous solution2 the following may be cited as a typical mixture3 ,aluminium nitrate1 #cjj parts2 magnesium nitrate1 #cjj parts2 chromium nitrate1 #c parts2 borax1 #e parts2 distilled water1 #aejj parts4 ,in order to secure that this fluid is applied to the head only1 a little organic colouring matter is generally added1 so that it may be clearly seen4 ,the solution is soaked on to the head from mechanically held felt pads1 which are kept at a convenient degree of saturation with the fluid by means of an ingenious compressed-air device4 ,the mantle is then rapidly dried in a hot-air chamber4 #eai ,vide ,d4 ,r4 ,p4 #bddiei1 ,march1 #aiab4 ,after the fixing and drying processes1 the head is #8finished4' ,the ordinary upright mantle is sewn together1 at the end which has been treated1 with carefully selected asbestos threads1 an opening of some ten millimetres being left1 and the asbestos is threaded diametrically across this opening--these diametrical threads support the mantle on its rod during use4 ,these operations were formerly done by hand1 when mantles of good quality were required1 but machine treatment is gradually coming into extended use4 ,several mantles now on the market are supported at the head by metal rings1 made from thin sheets of iron which have been plated with aluminium4 ,in petroleum lamps1 the mantle is usually supported from both sides by means of asbestos threads4 ,in the case of fabrics from which #8inverted' mantles are to be made1 fixing is carried out as usual at one end1 to a depth of about #ae cm4 ,after drying1 a strip of about #je cm4 width is bent over and sewn down1 and through this double band an asbestos thread is drawn1 by which the mantle is secured to a magnesia ring4 ,the lower end is drawn together in the shape of a hemisphere1 by means of threads drawn through the meshes of the fabric2 an opening of #f-h mm4 is sometimes left1 but in the more modern patterns the end is drawn almost completely together1 and after cutting is pressed out on a wooden shaper by a wooden mallet4 ,the product is now ready for burning off2 if it is to be marked1 it is stamped at this stage with a solution of didymium nitrate and methylene blue2 the former being only faintly coloured1 the organic dye is added to give a definite impression4 ,on ignition1 the nitrate is converted into the oxide1 which is deeply coloured1 and1 of course1 permanent4 ,burning off and ,shaping4--,for the production of mantles of the best quality1 these processes are usually carried out by skilled operators1 each mantle being treated separately4 ,very frequently1 however1 mechanical arrangements are employed4 ,the great objection to machine treatment of such a product lies in the fact that it must be identical for every mantle2 whereas it is exceedingly difficult to ensure that the original fabric1 and the processes of washing1 impregnating1 wringing1 and drying have been absolutely uniform4 ,the operation of shaping and hardening is a very delicate one1 and on the care with which it is carried out1 the quality of the mantle finally depends4 ,until quite recently1 only the cheaper kinds of mantles were machine-treated2 but as the uniformity of the fabric becomes more assured1 and the earlier operations more exact1 employment of machines at this stage will undoubtedly increase4 ,the prepared fabric is shaped on a suitable form1 and removed by a holder1 which supports it from the asbestos thread2 a flame is then applied to the head4 ,the burning-off proceeds readily1 once started2 when the upper half has been incinerated1 the flame is removed4 ,the weight of the unburnt portion prevents too rapid contraction taking place at first2 when the flame is removed1 the glow spreads slowly downwards1 and the shrinking is thus kept as uniform as possible4 ,the operation must be carried out under a ventilating hood4 ,the organic material of the fabric is completely oxidised1 and the nitrates are converted into oxides1 which retain the exact shape of the original fibres4 ,the skeleton now undergoes the process of shaping and hardening1 for which a #8radial' blowpipe flame is used4 ,the burnt-off product is placed over this2 the gas is supplied at an initial pressure of only a few inches of water1 which is increased towards the end of the operation4 ,the process commences at the head1 the mantle being slowly lifted and rotated so that it is shaped and hardened along the whole length4 ,by this means the oxide skeleton is not only suitably shaped1 but is rendered considerably more elastic and resistant4 ,for inverted mantles1 of course1 specially shaped burners are required4 ,the eyes of the operators must be protected from the glare by shades of green glass4 ,recently the processes of burning-off and hardening have been carried out by means of the same burner4 ,where machines are employed1 the prepared fabrics are burnt off on wire shapers1 usually in rows of ten2 mechanical arrangements for continuous ignition and motion and1 in the hardening1 for continuous elevation of the ash-skeleton1 are in use1 but the finished mantles maintain a uniform good quality only when the structure of the fabric and the earlier processes have been absolutely uniform4 ,collodinisation4--,the burnt-off mantle is now ready for use1 but is far too fragile for transport4 ,a method has therefore to be found by which the finished product can be protected for a time without detriment to its use for illumination4 ,mantles of artificial silk1 particularly those for use in high-pressure lamps1 are sometimes sent out without having undergone the final processes of burning off and shaping1 which1 in this case1 must be carried out on the consumer's burner4 #8,inverted' mantles also were formerly sent out after impregnation and drying4 ,in this condition1 of course1 the mantles are readily packed and transported1 and there is the additional advantage that the duty on the unburnt product is very much less than that on the finished mantle4 ,one of the earliest of ,auer's patents 7vide supra1 p4 #bga7 protected the process of collodinisation1 which is now extensively employed4 ,the oxide skeleton is dipped into a solution of collodion 7the mixed lower nitro-derivatives of cellulose1 or cellulose nitrates7 in a mixture of alcohol and ether1 to which1 to prevent shrinkage on drying1 a little camphor is added4 ,on account of the inflammability of the mixture1 the ethyl alcohol and ether are occasionally replaced by a mixture of methyl alcohol and acetone1 but with this less volatile mixture1 drying of course is slower4 ,after dipping1 the solvents are removed in a current of air1 leaving the mantle coated with an exceedingly thin film of collodion1 which increases enormously its power of resisting shock and vibration4 ,this film is not removed until the mantle is placed on the consumer's burner1 when on the application of a match it ignites instantly and burns away1 leaving the oxide skeleton in the condition to which it was brought in the final stage of hardening and shaping in the factory4 ,the process is now used for almost all kinds of mantles1 having been successfully applied in ,germany in recent years to those made from artificial silk4 ,the addition of small quantities of various inorganic salts1 e4g4 nitrates of zirconium1 magnesium1 platinum1 thorium1 etc41 to the collodion solution1 has been proposed2 these salts make the collodinised product extremely resistant1 but have a very harmful effect on the oxide ash when the collodion has been burnt off4 ,the collodinised mantles are cut to length on a trimming machine1 and are then ready for packing4 99 99 99 99 99 ,the present chapter may be concluded with a bare mention of a few disconnected details1 selected from the great mass of proposals1 suggestions1 and developments which have sprung up round the incandescent mantle industry4#ebj #ebj ,for a complete account of the mechanical developments1 the reader is referred to the monograph #8,beleuchtung und ,lichtmessung1' by ,dr4 ,brnstein1 in ,dammer's ,chemische ,technologie der ,neuzeit1 ,stuttgart1 #aiaj-aa1 ii4 #bdc-bff4 ,with regard to the composition of mantles1 numerous proposals have been made4 ,it is stated that thoria with #jbe per cent4 of uranic oxide1 ,,uo1 gives a light almost equal to that of the ,auer mantle4 ,zirconia with #jdj per cent4 of vanadium1 in the form of the pentoxide1 is said to give a splendid white light2 the vanadium oxide slowly volatilises1 but addition of an equivalent proportion of silica is said to prevent this4 ,langhans claims to have obtained a product equal in light-giving power to the ,auer mantle1 by using as impregnating fluid a solution of colloidal silica1 obtained by the addition of nitric acid to a solution of sodium silicate1 to which suitable quantities of rare earth nitrates are added4 ,bodies obtained by the use of very similar solutions give skeletons which are coming into extended employment for gas radiators4 ,the #8,sunlight' mantles use a mixture of thoria 7#ej per cent471 alumina 7#dj per cent471 and chromium sesquioxide 7#aj per cent474 ,a direction of development in which some success has been attained is the introduction of self-lighting devices4 ,the catalytic action of finely divided metals has been proposed in innumerable patents1#eba but these devices are unreliable1 and it seems doubtful if chemical methods will ever be successfully applied to the problem4 ,for the lighting of streets1 shops1 etc41 the #8by-pass' system is employed2 a tiny jet of gas burns continuously from a pin-hole nozzle1 which is momentarily increased1 when the main supply is turned on1 to such an extent that the gas issuing from the burner is ignited4#ebb #eba ,vide1 e4g4 ,d4 ,r4 ,p4 #aehigd and #beceej2 ,f4 #dagicd4 #ebb ,for automatic regulators for self-lighting1 vide ,j4 ,gasbel4 #aiaj1 #ec1 #dij4 ,an account of the innumerable forms of lamps and burners which have been introduced in the last twenty years would fill several volumes4 ,the theoretical grounds on which improvements in this direction are based are outlined in an able article by ,dr4 ,h4 ,bunte1 a recognised authority on incandescent lighting1 which appeared recently2#ebc for an account of some of the lamps which have been successfully applied1 the reader is referred to a recent ,french publication4#ebd #ebc ,j4 ,gasbel4 #aiaa1 #ed1 #dfi2 vide also ,pickering1 ,j4 ,gaslighting1 #aiaa1 #aac1 #aef4 #ebd ,l'clairage l'incandescence par le gaz1 ,lvy1 ,part ,i4 ,ch4 ,,iii4 ,,chapter ,,xx ,,artificial ,,silk--,,its ,,production ,,and ,,use ,,in ,,the ,,mantle ,,industry ,the history of the artificial silk industry1 since its foundation about the year #ahij1 illustrates curiously the rapidity with which isolated facts1 of apparently merely academic interest1 are seized upon and adapted to the needs of modern civilisation4 ,it is during this period1 especially1 that the bonds between science and industry1 in a dozen different directions1 have been drawn so close that to-day it is in many cases impossible to differentiate the two4 ,the pure science of to-day is the technology of to-morrow--and not always even of to-morrow1 but of to-day4 ,but we have moved even beyond this2 the industrial needs of the day are creating and extending our science at a rate which shows how relatively poor a stimulus has been the mere desire for knowledge4 ,such has been the history of the artificial silk industry4 ,no sooner had ,chardonnet shown that the preparation of a new fabric was not only possible but profitable1 than a thousand aspects of the problem were taken up4 ,patents were taken out on all sides--the majority1 as usual1 valueless1 one or two of great importance4 ,companies were formed1 factories built1 machines invented2 numberless applications were proposed1 mostly again worthless1 whilst patient research and innumerable experiments have carried one or two suggestions to a successful place in practice4 ,among these has been the adaptation of artificial silk to the manufacture of mantles1 which will be outlined in the present chapter4 ,before taking up this question1 however1 a short account of the manufacture of the fabric itself must be given4 ,chardonnet ,process4--,in the ,chardonnet process1 an account of which was published about #ahij1 continuous fibres are obtained by forcing through tiny jets a viscous solution of collodion1 or nitrocellulose1 as it has been misnamed1 in a mixture of ethyl alcohol and ether4 ,in the original form of the process1 the solution was forced into water1 which1 by removing the alcohol and ether1 caused an instantaneous coagulation of the surface1 so that a filament was obtained which could be wound directly on to a spool4 ,more generally1 however1 the jets deliver the solution into a chamber through which warm air is passed2 this is equally effective in removing the solvents and causing surface coagulation1 and the filaments are woven directly into threads of ten to forty strands1 according to the purpose for which the fabric is required1 fifteen to twenty being used for silk from which mantles are to be made4 ,on account of its inflammability1 the thread is denitrated by means of a solution of ammonium sulphide4 ,the raw material for the process is cellulose1 usually in the form of cotton4 ,treatment of this with a suitable mixture of concentrated sulphuric and nitric acids replaces some of the hydroxyl groups by the #8nitrate radicle1' ,,no1 a mixture of various nitrates of cellulose being formed1 in which the so-called tetra-1 penta-1 and hexa-nitrates predominate4#ebe ,the product1 cellulose nitrate or collodion1 very closely resembles the original cellulose in appearance and structure4 ,it is washed thoroughly to free it from traces of acid--which render it liable to explode spontaneously--and after drying1 dissolved in the minimum quantity of the mixed solvents2#ebf the solution is filtered from insoluble impurities through wads of cotton1 pressures of thirty to sixty atmospheres being required4 ,this filtration purifies and thoroughly mixes the solution1 so that perfect uniformity is obtained in the product4 ,the glass jets through which the solution is now forced1 under a pressure of forty to fifty atmospheres1 have a diameter of #jjh mm41 but the threads obtained contract on the removal of the solvents1 so that fibres of #jja-jjb mm4 are formed4 #ebe ,the cellulose esters are usually named as if they were derived from a compound ,c,h,o1 the formula for cellulose being 7,c,h,o7n4 ,thus the formation of the #8hexa-nitrate' would be represented-- ,c,h,o #f;,,hno ,c,h,o7,,no7 #f;,h,o4 #ebf ,in the ,lehner process1 in which collodion is also used1 larger quantities of solvent are employed1 so that much more dilute solutions are obtained2 these require low pressures to form the thread1 which is then hardened chemically4 ,chardonnet probably began his work about #ahhe4 ,it is interesting to observe that an ,englishman1 ,swan1 had proposed in #ahhc to use a solution of collodion in acetic acid1 fabrics prepared by his process being shown at the ,london ,exhibition of #ahhd4ebg #ebg ,vide ,bhm1 ,zeitsch4 angew4 ,chem4 #aiab1 #be1 #feg4 ,there is no account of this process in the ,english patent literature4 ,the ,pauly or ,cuprammonium ,process4#ebh--;,it has long been known that a solution of copper hydroxide in ammonia solution--,schweitzer's reagent--will dissolve cellulose4 ,the use of this solvent for the production of artificial silk was proposed about #aijj1 and the method has become a serious rival of the older ,chardonnet process4 ,the solvent is prepared on a large scale by passing air through an ammonia solution to which copper turnings have been added4 ,after addition of the cellulose1 and filtration1 the solution is forced through tiny jets into a bath of dilute acid1 which removes the copper and precipitates the cellulose again4 #ebh ,a full account of this and of the other processes employed in the manufacture of artificial silk will be found in the work of ,piest1 ,die ,zellulose1 ,stuttgart1 #aiaj4 ,the solution of cellulose by ,schweitzer's reagent is undoubtedly a chemical action4 ,cellulose is to be regarded as a polyhydric alcohol1 with one or several atoms of hydrogen of the hydroxyl groups replaceable by metals4 ,according to ,piest 7loc4 cit47 a #8,cupramine base' is formed by the replacement of this hydrogen by copper and the amino-group1 ,,nh4 ,the action of sodium hydroxide on cellulose1 however1 is generally regarded rather as an additive reaction1 the product1 #8alkali cellulose1' being usually written ,c,h,o1,na,o,h4 ,a careful chemical investigation alone can reveal the actual nature of the compound formed2 such an investigation1 apart from its scientific interest1 might yield results of considerable technical importance4 ,the ,viscose ,process4--,shortly after the introduction of the ,chardonnet process1 patents were taken out which protected a very cheap and simple method of dissolving cellulose1#ebi which had been discovered by two well-known ,english authorities4 ,cross and ,bevan4 ,they found that mercerisation1 i4e4 the action of the sodium hydroxide on cellulose1 produces a swollen1 transparent mass1 which very readily takes up carbon disulphide4 ,when exposed to the action of this liquid for three or four hours1 at ordinary temperatures1 the mass swells further1 gelatinising and becoming soluble in water4 ,on treatment with water1 a yellowish1 extremely slimy solution is obtained1 from which cellulose is precipitated on prolonged standing1 by heating1 or by oxidation4 ,the substance is apparently a cellulose xanthate1 and may be written ,na,s,,cs,o,c,h,o1,na,o,h4#ecj ,on account of the extremely viscous nature of the aqueous solution1 ,cross and ,bevan gave it the name ,viscoid4 #ebi ,vide1 e4g4 ,cross1 ,bevan1 and ,beadle1 ,d4 ,r4 ,p4 #gjiii1 granted ,september1 #ahic4 #ecj ,vide ,beltzer1 ,zeitsch4 angew4 ,chem4 #aijh1 #ba1 #agca4 ,during the last few years this method of dissolving cellulose has been employed in the manufacture of artificial silk1 under the name #8,viscose ,process4' ,the product obtained is very suitable for the manufacture of incandescent mantles1 and is considerably cheaper than either the ,chardonnet or ,pauly silk4 ,the ,acetate ,process4--,quite recently numerous experiments have been carried out with the object of finding methods for employing the cellulose esters of organic acids in the preparation of fabrics4 ,the acetate1 which is generally used1 gives solutions from which fibres can be obtained which are comparable to natural silk in strength1 and which have the further advantage of being non-inflammable1 and far less readily affected by water than artificial fabrics obtained by the above methods4 ,it is prepared by treating cellulose with dilute acid1 by which the so-called #8hydrocellulose' is obtained2 this is treated with a mixture of glacial acetic acid and acetyl chloride1 and the whole1 after addition of a little concentrated sulphuric acid1 warmed to #fe-gj;,c4 ,as early as #ahid1 ,cross and ,bevan#eca had patented a process for this preparation by the action of acetyl chloride in the cold on an intimate mixture of cellulose and zinc chloride4 #eca ,e4 #ifgf1 #ahid4 ,from the solution obtained1 the acetates are precipitated by water1 washed and dried4 ,the mixture of esters dissolves in chloroform1 nitromethane1 acetic acid1 phenol1 pyridine1 etc41 and is re-precipitated by addition of alcohol1 benzene1 or ligroin 7petroleum ether74 ,on account of its non-inflammable character1 cellulose acetate1 as the product is called1 is being used instead of the nitrate in the manufacture of celluloid2 it is also used for non-inflammable cinematograph films4 ,fibres can be obtained by forcing the solutions through jets1 and removing the solvent1 as in the above processes2 these are spun into threads which are coming into increasing use1 on account of their extremely low conducting power1 for the insulation of very fine electric leads4 ,the product is at present too expensive1 however1 for use in the textile industries1 or for the manufacture of mantles4 ,a solvent which had at one time some technical importance is zinc chloride4#ecb ,the concentrated aqueous solution of the salt will take up cellulose in considerable quantity2 and the solution has been used in the preparation of carbon filaments for glow lamps4 #ecb ,gulbrandsen1 ,prog4 ,age1 #aiab1 #cj1 #gg2 ,wynne and ,powell1 ,e4 #afhje1 ,december1 #ahhd4 ,the fabrics prepared by the processes which have been mentioned above are of great technical value4 ,in lustre they far surpass natural silk1 and they take dyes very well1 but owing to the ease with which they tear1 they cannot be woven alone for textiles1 but are always used in #8mixed' materials4 ,the acetate silk1 which approaches the natural fibre in strength1 is not much less expensive4 ,whilst the price of natural silk is roughly #ce francs per kilo4 7approx4 #acs4 #c;d4 per lb471 the costs of production of the artificial fabrics are--,chardonnet #ae frs41 ,pauly #ab frs41 ,viscose #g frs4 per kilo4 7respectively #es4 #h;d41 #ds4 #f;d41 and #bs4 #h;d4 per lb474 ,artificial silk1 however1 has uses distinct from the natural fibre1 and is at present a competitor with it in one or two small fields only4 ,thus the production of natural silk is ten times that of artificial silk 7#ej1jjj1jjj kilos4 per annum to #e1jjj1jjj kilos47 in spite of the difference in price4 ,artificial silk is very susceptible to the action of water1 which weakens it very considerably4 ,its resistance is said to be greatly increased by the action of formaldehyde2 the fabric is plunged into a bath containing an aqueous solution of the aldehyde1 to which a little lactic acid has been added4 ,the chemistry of the change is discussed at length by ,beltzer 7loc4 cit474 ,the threads of artificial silk far surpass in lightness those spun from vegetable fibres4 ,a thread of twenty strands weighing one pound avoirdupois would be more than twenty miles long4 ,at the same time the filaments have not the irregular tubular structure of vegetable fibres1 but are solid cylinders4 ,the fact that the filaments are continuous1 so that there is relatively little torsion in threads spun from them1 gives artificial silk its great advantage over the natural vegetable fibres for the manufacture of mantles4 ,for this purpose the ,pauly or ,cuprammonium silk is most suitable1 though ,viscose silk is almost as good2 the fibre obtained by the ,chardonnet process is not quite so useful in this direction4 ,the ,manufacture of ,mantles from ,artificial ,silk4--,whilst the fabrics made by the various processes outlined above are more expensive than the cotton and ramie formerly exclusively used in the mantle industry1 they have the advantage1 in addition to the fact that they produce better and more lasting mantles1 that they do not need the laborious and troublesome process of washing which is so essential in the case of the vegetable fibres4 ,from the nature of the methods used in its manufacture1 artificial silk can contain no mineral residue2 hence the fabric is immediately ready for impregnation4 ,as early as the year #ahib ,schlumberger and ,sinibaldi proposed the use of ,chardonnet silk for the manufacture of mantles2 but their patent1 a ,belgian one1#ecc attracted little attention1 although they stated clearly that the denitrated silk will readily take up the lighting fluid4 ,ignorance of this fact deferred the successful application of this fibre for ten years4 ,in #ahid ,de ,mare suggested the preparation of mantles by addition of the necessary salts to the collodion solution before squirting2 in the following year ,knfler used the same process1 recommending in addition the use of ammonium sulphide to denitrate the impregnated threads4 ,these two attempts1 which were found to be unworkable1 owing to the difficulty of obtaining a homogeneous product before squirting1 were merely efforts to compete against the ,auer monopoly1 resting on ,welsbach's patents1 which covered impregnation of any natural fibre4 ,in ,knfler's process1#ecd the salts were dissolved in alcohol and added to the collodion solution1 which was then forced through jets into water1 to which ammonia was added to prevent removal of the nitrates in solution2 the threads were then denitrated with ammonium sulphide4 ,the ammonia treatment of course converts the nitrates into the insoluble hydroxides1 a departure which was followed in most of the numerous patents inspired by ,knfler's process4 #ecc ,vide ,bhm1 ,zeitsch4 angew4 ,chem4 #aiab1 #be1 #feg4 ,apparently this patent was not taken up2 no account of it has been found in the published patents of the ,belgian ,government4 #ecd ,e4 #aajch1 #ahie1 granted ,july1 #ahie4 ,the first indications of the method which ultimately led to success are to be found in a patent taken out by ,plaisetty1 in #aija4ece ,the specification protects the addition of thorium and cerium hydroxides to the cuprammonium solution of cellulose1 but apparently without any inkling of the results that were to follow1 and more or less incidentally1 he includes in this patent the impregnation of the finished fabric and the subsequent treatment with ammonia4 ,in the following year he applied for a ,german patent1#ecf which was granted in ,may1 #aijc1 in which he definitely protects the impregnation of the finished fabric1 and the ammonia treatment1 the fabric being then washed and dried1 and burnt off as usual4 #ece ,e4 #bjgdg1 #aija4 #ecf ,d4 ,r4 ,p4 #adabdd4 ,impregnation4--,since the filaments from which artificial silk is obtained are solid and rod-like in form1 as opposed to the tubular structure of cotton and ramie filaments1 it is rather surprising that the fabric should take up the lighting fluid in the necessary quantity 7vide p4 #bie74 ,it is found that a #ej per cent4 solution of nitrates gives the best results1 the impregnation requiring half an hour2 a warm bath is usually employed4 ,it is usual to add to the bath a quantity of thorium hydroxide1 since the thorium nitrate of commerce generally contains nitric acid1 which has a bad effect on the fabric4#ecg ,the excess of solution is removed by means of a glass or porcelain centrifuge1 not1 as with cotton or ramie mantles1 by use of a wringer2 drying must be carried out very slowly4 ,the fabric is not cut into lengths before impregnation1 as in the case of cotton or ramie1 but is immersed in the lighting fluid in long strips4 #ecg ,vide ,buhlmann1 ,d4 ,r4 ,p4 #ahhdbg1 #aijg2 also ,e4 #fhbh1 #aijg4 #8,fixing4'--,if the dried fabric1 impregnated with the necessary salts1 be finished and burnt off in the usual way1 the oxide skeleton is extremely fragile1 and soon falls to powder4 ,the reason for this lies probably in the explosive decomposition of the nitrates1 the weight of organic matter relative to the salts being very much less than in the case of ramie or cotton fabrics 7vide p4 #bie74 ,the additional ammonia bath advocated by ,knfler 7vide supra7 was therefore adopted by ,plaisetty1 and the nitrates in the dried impregnated fabric are converted into hydroxides by this treatment4 ,for this process1 to which the name #8,fixing' has been given by ,bhm1 numberless alternative proposals have been made4 ,plaisetty's ammonia fixing gives a mantle which1 after burning off1 is exceedingly elastic and strong1 but it is nevertheless open to serious objections4 ,thus the nitrates may be to some extent dissolved out by the fixing bath before precipitation of the hydroxides has occurred2 to remedy this1 the impregnated fabric must be very thoroughly dried before fixing1 and in this case1 apart from the trouble involved1 the acid of the commercial nitrates will attack the fabric unless addition of thorium hydroxide has been made to the impregnating fluid4 ,again1 the conversion into oxides is not complete1 the outer layer first formed preventing free diffusion of the alkaline fluid4 ,finally1 since ammonium nitrate is formed in the reaction1 a very thorough washing is necessary to remove this salt4 ,it would be impossible to mention all of the numberless proposals which have been put forward for fixing2 nor are the great majority worthy of mention4#ech ,one of the most important was that of ,albrecht1#eci by which hydrogen peroxide is substituted for ammonia4 ,this reagent1 as is well known1 precipitates from solutions of thorium salts #8peroxide' compounds 7vide p4 #bee72 from the fabric impregnated with the nitrate1 free nitric acid is liberated in the reaction4 ,since the peroxide is soluble in nitric acid1 two baths are used1 the fabric being allowed to remain for a short time only in the first1 which becomes strongly acid1 and being then transferred to the second1 in which the precipitation is completed4 ,the burning off of the product so treated proceeds quite quietly1 and leaves a very hard and elastic skeleton4 ,the method1 however1 has the grave disadvantage that cerium salts are not precipitated under these conditions1 but escape into the solution4 ,to remedy this1 arbitrary additions of cerium nitrate are made to the fixing bath1 but the percentage of cerium1 and therefore the lighting power 7vide p4 #bic7 of mantles fixed by this method is liable to fluctuate4 ,a modification has been introduced#edj in which various salts are added to the hydrogen peroxide fixing baths to prevent the withdrawal of the cerium salt2 these are chiefly acetates of the alkali metals and allied compounds4 ,the fabric requires washing after this treatment4 #ech ,a large number of patents are mentioned by ,bhm1 ,j4 ,gasbel4 #aiji1 #eb1 #hee4 #eci ,d4 ,r4 ,p4 #ahhdbg1 ,september1 #aijg2 ,e4 #aebie1 #aijg4 #edj ,vide ,e4 #bbdj1 #aijh4 ,cerofirm ,gesellschaft1 by ,brit4 ,cerofirm ,co4 ,a rather similar proposal#eda substitutes for ammonia an alkaline solution of hydrogen peroxide1 obtained by dissolving sodium peroxide in water4 ,after saturation for a minute or so1 the fabric is wrung out and dried1 there being no necessity1 according to the patent1 for any subsequent washing4 ,the same company in an earlier patent#edb suggest a fixing bath of #8an alkali or amine with an acid which can form insoluble basic double salts with the earth metals1' the said salt to be precipitated on the fibre1 whilst an alkali or amine nitrate goes into solution2 acetic and benzoic acids and phenol are mentioned4 ,apparently this process did not give satisfactory results4 ,the same may be said of the hypochlorite method of ,visseaux4#edc ,equally interesting1 and doubtless equally practical is the proposal#edd to treat the dried impregnated mantle with ozone in a closed chamber1 which possibly inspired the even more original suggestion#ede that the fabric be first washed in ozonised water1 dried1 then impregnated and dried1 and finally treated with ozone4 ,according to yet another ,french patent1#edf the impregnated and dried fabric is to be treated with an alcoholic solution of hydrofluoric acid1 which will give a viscous insoluble mixture of thorium and cerium fluorides in the fabric1 and at the same time will remove any impurities4 ,another patent#edg proposes the use of hydrazine and similar bases1 cerium nitrate being added to the fixing solution4 #eda ,d4 #bdgidj1 ,june1 #aiab2 ,f4 #dcjdag1 ,august1 #aiaa4 #edb ,f4 #djcdcc1 ,september1 #aiji1 ,bruno ,co4 #edc ,f4 #djhhjg1 ,february1 #aiaj4 #edd ,f4 #dadgjj1 ,june1 #aiaj4 #ede ,f4 #dbbfdc1 ,january1 #aiaa4 #edf ,f4 #dbfaef1 ,april1 #aiaa4 #edg ,e4 #aaijd1 #aiji4 ,innumerable suggestions have been made for fixing by means of ammonia gas1 or vapours of organic bases4#edh ,an ,english patent granted in ,february #aiajedi protects #8various improvements1' which consist in carrying out a preliminary treatment with steam1 impregnation with the solution of nitrates1 conversion of nitrates into oxides either by steam carrying ammonia1 pyridine1 etc41 or by the action of these vapours without steam in a vacuum1 all in one chamber1 which can be exhausted or filled with various solutions or vapours as required4 #edh ,vide1 e4g4 ,d4 ,r4 ,p4 #aiifae of ,june1 #aijh4 #edi ,e4 #beedi1 #aijh4 ,more recently1 the use of organic salts of thorium and cerium for impregnation has been proposed by ,dr4 ,f4 ,w4 ,wirth2#eej in fixing the impregnated fabric with hydrogen peroxide1 the cerium is not removed in solution1 since the weak organic acid formed will not dissolve cerium peroxide4 ,the same author has also suggested#eea the addition to the fixing bath of substances which absorb oxygen from the air--e4g4 sodium hydrogen sulphite1 resorcinol1 tannin--to prevent removal of cerium4 ,he has also advocated impregnation with amorphous salts1#eeb which will obviate the necessity for any subsequent fixing treatment1 the hypophosphites and double compounds with ammonium oxalate being specified4 ,attempts have been made to achieve the same end by other methods4 ,thus ,silbermann#eec has proposed a preliminary treatment with alkalies 7mercerisation72 the fabric is treated with concentrated sodium hydroxide solution in absence of air for half an hour1 pressed through rollers1 and plunged into the impregnating solution4 ,two years previously a patent was taken out by ,drossbach#eed to protect the use of colloidal solutions of the hydroxides4 ,to a boiling suspension of well-washed1 freshly-precipitated thorium hydroxide1 a solution of a small quantity of the nitrate is gradually added2 after half an hour a colloidal solution is obtained1 which1 after the addition of the required quantity of cerium nitrate1 and dilution to a suitable extent1 is employed directly for impregnation4 ,the patent states that this solution is more readily absorbed than the ordinary nitrate solution1 but the statement has been questioned4 #eej ,chem4 ,zeitg4 #aiaa1 #ce1 #geb4 #eea ,zeitsch4 angew4 ,chem4 #aiab1 #be1 #ibb4 #eeb ,chem4 ,zeitg4 #aiaa1 #ce1 #geb4 #eec ,chem4 ,zeitg4 #aiaa1 #ce1 #ajcg4 #eed ,d4 ,r4 ,p4 #babhdb1 ,august1 #aiji2 vide also ,kreidl and ,heller1 ,e4 #aghfb1 #aiji1 and ,d4 ,r4 ,p4 #bbhbjc1 #aiaj4 ,artificial silk itself is of a colloidal nature1 the solidification of the filaments of cellulose during the manufacture being rather in the nature of a coagulation than of a precipitation2 it is to this fact that the fibres owe their solid1 rod-like structure1 and it is probably this circumstance also which determines the very intimate absorption of the hydroxides or peroxides produced by fixing4 ,it is well known that colloidal substances under some circumstances possess the property of clinging tenaciously to foreign bodies1 exhibiting the so-called phenomenon of adsorption4 ,the strength and elasticity of the oxide skeleton1 obtained when the fixed and dried fabric is subjected to the operation of burning off1 are presumably to be referred to such a relation between the cellulose of the fibres and the insoluble thorium and cerium compounds1 precipitated by one of the methods of fixing described4 ,the ,final ,stages4--,the treatment of the fabric after impregnation and fixing differs only slightly from that used for the impregnated ramie and cotton products4 ,the dried strips are cut into suitable lengths1 and the head is drawn together with asbestos and threaded across4 ,no tulle or gauze is required1 the end being simply turned down before threading4 ,after the ordinary strengthening process for the head 7vide p4 #bif7 the process of manufacture was1 until recently1 finished1 the goods being sent out in the unburnt condition1 on account of the difficulties of collodinisation4 ,these have now been overcome1 so that the mantles are burnt off and collodinised as usual4 ,burning off and shaping are now frequently effected in one operation by machine2 the nature of the methods by which the fibre is made produces a uniform fabric1 and if the earlier processes are carefully carried out1 a uniform product is obtained1 which is therefore suitable for machine treatment4 ,,chapter ,,xxi ,,other ,,technological ,,uses ,,of ,,the ,,cerium ,,and ,,yttrium ,,elements1 ,,zirconium ,,and ,,thorium ,the technical uses of the members of this group of the elements we are considering1 apart from the employment in the manufacture of incandescent mantles1 are at present very restricted4 ,innumerable proposals for the employment of the compounds of cerium and the allied metals1 which are obtained in such large quantities as by-products in the thorium industry1 have been put forward1 but the actual extent to which they are utilised is so small that only an insignificant fraction of the available quantities is annually required4 ,in the metallic form1 a limited application is found for various alloys1 e4g4 the so-called pyrophoric alloys1 misch metal1 and the magnesium and aluminium alloys4 ,various compounds of the elements1 as well as some alloys1 have been suggested for use in arc-lamp electrodes1 and the use of the metals themselves1 as well as of various salts1 for the manufacture of flashlight powders1 is protected by several patents4 ,investigations have been made to determine the value of the oxides and sulphates as catalysts in the contact process for the manufacture of sulphuric acid1 and one patent states that the yield obtained is equal to that given by platinised asbestos4 ,cerium salts have been proposed for tanning1 and in the preparation of enamels2 cerium sodium sulphate is used in the catalytic oxidation of aniline to aniline black4 ,the oxalate has a very slight use in medicine4 ,the oxidising power of ceric salts is of some use in photography2 ceric sulphate in acid solution is also said to be an efficient oxidising agent for aromatic hydrocarbons4 ,on account of the deep colour of the higher oxide of praseodymium1 didymium salts find a limited application for marking textiles4 ,compounds of the yttrium group have at present no technical importance4 ,they were formerly used to some extent for the manufacture of filaments for ,nernst lamps1 but with the introduction of metal filament lamps in electric lighting1 the demand for ,nernst lamps and consequently for the yttria oxides1 has to a very great extent died away4 ,zirconium and its compounds1 on the other hand1 promise to become of some technical importance4 ,the metal received considerable attention in the earlier stages of experimental work on metallic filaments for electric lighting1 but it has been shown that its melting-point is not sufficiently high to allow of extended use in this direction4 ,the carbide has been proposed for the same purpose1 but is even less suitable2 this compound1 however1 on account of its great hardness1 is likely to find employment as an abrasive1 and in glass-cutting4 ,the oxide1 which occurs in nature in an impure form as the mineral ,baddeleyite 7q4v471 is employed in the manufacture of #8,siloxide' glass and of enamels1 as a pigment and polishing agent1 and in various forms of lamps1 e4g4 the ,nernst and ,bleriot lamps1 the ,drummond light1 etc4 ,far more important1 however1 is its use for fire-resistant crucibles1 furnace linings and supports1 etc41 for which its refractory nature renders it particularly suitable4 ,on account of its high specific gravity and non-poisonous character1 it has been proposed for use in the ,rntgen ray examination of the human body4 ,quite recently1 metallic zirconium has been employed in metallurgy2 addition of small quantities1 in the form of suitable alloys1 is said to secure sound castings1 with increased strength and resistance to acids4 ,,the ,,cerium ,,group ,pyrophoric ,alloys4--,it has long been known that the metals of the cerium group possess the property1 when scratched or struck1 of throwing off glowing particles2 this power of emitting sparks is not lost when the metals are alloyed1 so long as the percentage of foreign metal is not allowed to become too high4 ,in a patent#eee protecting the use of various #8pyrophoric alloys1' as these spark-giving alloys are called1 ,auer states that the pure metals do not show this property1 which only appears when foreign metals are present2 he accordingly patents alloys of the cerium metals with iron1 specifying particularly the alloy with #cj per cent4 of the latter element4 ,auer's statement has been contradicted1#eef and it seems to be generally accepted that misch-metal#eeg of ordinary technical purity has the property of sparking when scratched4 ,this alloy of the cerium metals1 however1 is far too soft to be useful for the purpose1 and the addition of some foreign element is required to obtain the strength1 hardness1 and brittleness necessary in the various forms of #8lighters4' ,besides the addition of iron1 the use of tin1 lead1 zinc1 cadmium1 silicon1 etc41 has been patented4#eeh #eee ,e4 #afhec1 #aijc2 ,d4 ,r4 ,p4 #aedhjg4 #eef ,vide ,bhm1 ,chem4 ,zeitg4 #aiaj1 #cd1 #cfa4 #eeg ,the crude mixture of cerium1 lanthanum1 neodymium1 praseodymium1 samarium1 etc41 with small quantities of iron and other metals1 obtained by reduction of the earth-compounds formed as by-products in the thorium industry1 is technically known as #8misch-metal4' #eeh ,f4 #dcijeh1 ,march1 #aiab4 ,various forms of these lighting devices are manufactured2#eei in all of these the sparks produced by scratching the pyrophoric alloy with hardened steel1 by means of some simple mechanical device1 is caused to ignite a fragment of tinder1 or a wick supplied with a suitable liquid1 e4g4 methyl alcohol1 benzene1 or petrol4 ,in the numberless forms of cigarette-lighters at present before a somewhat indifferent public1 the friction is obtained by means of a toothed wheel1 actuated by a spring which is released when the device is opened4 ,many forms of gas lighter are also on the market1 but the demand for them is very small4 ,many attempts have been made to adapt the device to the ignition of the ,davy miners' lamp1 but none have been successful1 since it is impossible to prevent the sparks flying through the gauze4 ,much work has also been spent in efforts to utilise the pyrophoric alloys for the automatic ignition of incandescent gas-lamps1 but these have been equally unsuccessful1 so that it may be said that important technical applications of this interesting property have still to be made4 #eei ,vide ,bhm1 ,chem4 ,zeitg4 #aiaj1 #cd1 #cgg2 also ,kellermann1 ,die ,ceritmetalle und ihre pyrophoren ,legierungen1 ,wilhelm ,knapp1 ,halle1 #aiab1 pp4 #id et seq4 ,auer prepared his alloys by addition of iron1 or other heavy metal1 to the fused mixture of cerium metals obtained in the electrolytic apparatus employed for the production of the latter4 ,they can1 however1 be prepared by fusing together the required quantities of foreign metal and misch-metal1 the latter being obtained by processes other than those of electrolysis usually employed4 ,the rare metals were obtained by the earlier chemists in a very impure state by reduction of the halogen or double halogen compounds with sodium or potassium4 ,more recently#efj much purer products have been obtained--especially in the case of zirconium--by the action of metallic calcium1 in the form of powder1 on the oxides4 ,another method1#efa which has been employed in the preparation of metallic filaments for lamps1 consists in heating the oxides with powdered magnesium in an atmosphere of hydrogen or nitrogen2 by this means1 hydrides or nitrides are obtained1 which on heating decompose into the gas and the metal4 #efj ,vide ,kuzel and ,wedekind1 ,e4 #bcbae1 #aiji4 #efa ,electrodon ,gesellschaft1 ,d4 ,r4 ,p4 #aedfia1 ,september1 #aijd4 ,the ease with which misch-metal and its alloys with iron and other elements throw off glowing particles when struck is due to the low ignition temperature of cerium1 and the energy with which it combines with oxygen4 ,when such alloys are scratched1 small fragments are struck off1 which are raised to the ignition temperature by the heat of friction4 ,it is generally accepted1 however1 that this explanation is by no means a complete one1 and the existence of a pyrophoric suboxide was suggested4#efb ,the theory was advanced that the pyrophoric properties of the alloys were due primarily to the formation on the surface of a film of this sub-oxide1 and the partial oxidation of cerium alloys1 protected by patent 7loc4 cit471 was said to cause a marked increase in the ease with which sparks could be obtained4 ,in this connection1 an experiment of ,hirsch1 who has thoroughly investigated the properties of metallic cerium1#efc is of interest4 ,he found that when the element is warmed in a sealed glass bottle1 a black powder forms on the surface1 which1 when the bottle is opened1 ignites spontaneously4 ,it is probable that this black sub-oxide plays an important part in the production of sparks from the ordinary pyrophoric alloys4 #efb ,vide ,f4 #djgaag1 ,december1 #aiji4 #efc ,met4 ,chem4 ,eng4 #aiaa1 #i1 #edc4 ,other ,alloys4--,on account of the great affinity of the cerium metals for oxygen1 misch-metal has been suggested as a reducing agent1#efd as have also the alloys of cerium and magnesium2#efe the formation of the latter is endothermic1 so that they act much more vigorously than either metal separately4 ,the alloys of cerium with tin and aluminium have been thoroughly investigated from the stand-point of metallography1 by ,vogel4#eff ,it has recently been claimed that the addition of very small quantities of cerium to aluminium has a very marked effect1 the rare earth metal acting as a purifying agent1#efg and greatly improving the properties of the aluminium4 ,the cerium may be introduced as fluoride1 either to the electrolytic bath in which the aluminium is being prepared1 or to the latter metal1 after preparation1 in the fused state4 ,the most favourable effect is said to be produced by #jb per cent4 of cerium4 #efd ,vide1 e4g4 ,escales1 ,d4 ,r4 ,p4 #adehbj1 ,october1 #aijc4 #efe ,hirsch1 loc4 cit4 #eff ,zeitsch4 anorg4 ,chem4 #aiaa1 #gb1 #cai2 #aiab1 #ge1 #da4 #efg ,borchers and ,barth1 ,d4 ,r4 ,p4 #bdfdhd1 ,may1 #aiab4 ,applications of the ,cerium ,compounds4#efh--,one of the earliest investigations in which cerium compounds were examined with a view to technical employment1 was that of ,kruis1#efi who made experiments on the comparative value of the salts of different metals as catalysts in the manufacture of aniline black4 ,he showed that a solution of aniline with an oxidising agent 7potassium chlorate or chromate7 develops no colouration unless a salt of a heavy metal is present4 ,in the case of the fabric impregnated with the solution1 the only metals of which compounds were found suitable for producing a colour were copper1 which was then generally used for the purpose1 and cerium1 iron1 and manganese4 ,of these1 cerium1 used in the form of the double sulphate1 was found to be by far the most suitable1 and moreover to have the advantage that only small quantities are required2 the price was at that time too high to allow of its use1 but it has since been employed4#egj ,cerium compounds have also been proposed as mordants for alizarin1#ega but they do not appear ever to have come into general use4 #efh ,an account of the various suggestions for the technical employment of the rare earth elements1 by ,dr4 ,max ,speter1 will be found in ,dammer1 ,die ,chemische ,technologie der ,neuzeit1 ,stuttgart1 #aiaj1 vol4 i4 pp4 #ejj-ejd4 #efi ,dingl4 ,polyt4 ,j4 #ahgd1 #bab1 #cdg4 #egj ,vide ,buhrig1 ,dingl4 ,polyt4 ,j4 #ahgi1 #bca1 #gg2 and ,abstr4 ,chem4 ,soc4 #ahgi1 #cf1 #fhc4 #ega ,vide ,witt1 ,chem4 ,ind4 #ahif1 #ai1 #aef4 ,in photography1 ceric sulphate has been employed for some time for the purpose of #8reducing1' i4e4 removing silver from over-developed negatives4#egb ,it is said to act very evenly and rapidly1 the small quantity of free sulphuric acid required to hold the salt in solution having no bad effect4 ,more recently1 cerium salts have been proposed for use in colour photography4#egc ,an emulsion is obtained by adding salts of iron1 uranium1 or cerium to a colloidal solution of albumen in ammonia1 borax solution1 or sodium carbonate solution2 this is spread on the paper or negative1 and is said to be readily sensitive to light4 #egb ,vide ,lumire1 ,bull4 ,soc4 franc4 ,photog4 7#b7 #aijj1 #af1 #ajc4 ,also ,e4 #dgj1 #aijj4 #egc ,fateau1 ,e4 #bjgdj1 #aijg4 ,the crude mixture of cerous sulphate with basic sulphates of other elements of the cerium group1 which has been patented for use as a catalyst in the contact process for the manufacture of sulphuric acid1#egd is prepared from the earth compounds obtained as by-products in the treatment of monazite4 ,these are converted into the sulphates1 and1 after evaporation of the excess of sulphuric acid1 heated for several hours at a low red heat 7#cjj-fjj;,c474 ,the porous mass is then broken1 and is ready for use4 ,it is stated that a nearly quantitative yield of sulphur trioxide is obtained1 and that the mixture acts more efficiently than pure cerous sulphate4 ,the reaction is said to depend on the continuous formation and decomposition of the ceric salt1 thus3 ,ce7,,so7 ,,so ,o #b;,ce7,,so7 #b;,ce7,,so7 ,ce7,,so7 ,,so ,o #egd ,hlbling1 ,d4 ,r4 ,p4 #adbadd and ,f4 #cbfcba of ,may1 #aijc4 ,this process does not appear to have come into general use4 ,a general patent had been taken out in #aija1 protecting the use of oxides of the rare earth elements for #8high-temperature catalysis' in the manufacture of sulphuric acid1#ege but the oxides do not seem to be very efficient4#egf #ege ,meister1 ,lucius and ,brning1 ,e4 #ache1 #aija4 #egf ,vide ,plddemann1 ,dissertation1 ,beitrag zur ,aufklrung des ,schwefelsurekontaktprozesses1 ,berlin1 #aijg4 ,it has also been proposed to utilise the oxidising power of ceric salts in acid solution#egg for the preparation of aldehydes1 quinones1 etc41 from aromatic hydrocarbons1 for which purpose they are claimed to be more efficient than chromates4 ,by the use of a crude cerium dioxide 7#fj-gj per cent4 ,ce,o7 obtained by the ignition of the by-products of the thorium industry1 good yields were obtained of benzaldehyde1 naphthaquinone and anthraquinone from toluene1 naphthalene and anthracene respectively4 #egg ,meister1 ,lucius and ,brning1 ,d4 ,r4 ,p4 #aehfji1 ,march1 #aije4 ,garelli#egh has examined the action of cerium salts in tanning2 he states that with neutral solutions1 effects very similar to those produced by aluminium salts are obtained1 but ,eitner1 who has also examined the question1#egi is of opinion that the cost of isolating and purifying the salts from the monazite residues renders their employment for this purpose impossible4 #egh ,j4 ,soc4 ,chem4 ,ind4 #aiab1 #ca1 #hcj4 #egi ,ibid4 #aiaa1 #cj1 #aabh4 ,the fluoride1 silicofluoride1 and dioxide have also been proposed for the preparation of enamels1#ehj but do not give satisfactory results4 #ehj ,rickmann and ,rappe1 ,d4 ,r4 ,p4 #iiafe1 ,september1 #ahih2 also ,d4 ,r4 ,p4 #bjcggc1 ,october1 #aijh4 ,several patents protect the use of rare earth compounds for flashlight powders4 ,for most of the mixtures covered1 it is claimed that the usual defects of fumes1 slow firing1 etc41 are absent4 ,the usual recipes#eha are for magnesium or aluminium powder with chromates1 nitrates1 or similar salts of thorium1 cerium1 etc42 in one case#ehb the rare earth metals1 alloyed with barium1 silicon1 uranium1 or titanium1 are to be used with #8an oxidising agent which leaves a non-volatile residue4' ,none of these mixtures appears to have been successful4 #eha ,vide1 e4g4 ,e4 #adfib1 #aijh2 ,d4 ,r4 ,p4 #aehbae4 #ehb ,f4 #djcgbb1 ,october1 #aiji4 ,cerium compounds have also been proposed for use in arc-lamp electrodes2 it is claimed that they give a very intense light1 one patent#ehc adding that the presence of cerium peroxide and a little fluorspar causes the arc to burn evenly and quietly4 ,in another1 the use of a mixture of tungstates or molybdates of the alkaline earths1 with fluorides of the rare earth elements is protected2#ehd the use of pyrophoric alloys1 either entirely1 or for the core of the electrode1 has also been suggested4#ehe #ehc ,e4 #dadgjg1 ,june1 #aiaj4 #ehd ,f4 #dcajdj1 ,august1 #aiaa2 also ,e4 #bacgd1 #aiji4 #ehe ,e4 #haej1 #aiji4 ,the ,nernst ,lamp4--,the first efforts which were made for the employment of electricity in illumination endeavoured to utilize the heat produced1 when a current traverses a very thin metallic filament1 to raise the conductor to incandescence4 ,numerous efforts were made to adapt platinum to this purpose1 but its melting-point was finally admitted to be too low2 at length it was found possible to produce carbon filaments1 and the well-known carbon lamps came into use4 ,numerous attempts were made to effect improvements2#ehf one plan was to coat the carbon filament1 after its production1 with a skin of metallic conductor1 and zirconium and thorium were among the metals proposed in this connection4#ehg ,the first really important advance1 however1 was effected by ,nernst1 who took up the study of #8conductors of the second order1' and within a few months succeeded in adapting these to the purposes of illumination 7#ahig-ahih74 ,the ,nernst lamps gave a very intense white light with considerably less consumption of electricity than the carbon filament lamps2 they enjoyed a very considerable vogue for some years1 but have been almost entirely displaced by the cheaper metal filament lamps1 which were occupying the attention of ,auer von ,welsbach at the time ,nernst perfected his invention4#ehh #ehf ,the reader is recommended to consult the ,jahresberichte ber die ,leistungen der ,chemischen ,technologie of ,fischer1 ,section #8,beleuchtung1' for the years #ahih-aija inclusive1 from which some idea may be obtained of the innumerable proposals and suggestions1 usually protected by patent1 which were put forward at this time4 #ehg ,vide1 e4g4 ,d4 ,r4 ,p4 #aeciei4 #ehh ,vide ,e4 #aece1 #acaaf and #agehj1 #ahih4 ,in his first patent1#ehi ,nernst proposed the use of a rod of magnesia or zirconia as filament2 these oxides1 which belong to his class of conductors of the second order1 are non-conductors at ordinary temperatures1 but their resistance decreases as the temperature rises1 so that at high temperatures they will conduct electricity at the ordinary voltage4 ,the preliminary heating was at first effected by means of a ,bunsen burner1 but a later patent#eij of the same year protects a method of heating by means of a platinum spiral in an auxiliary circuit1 which is automatically cut out when the current in the main circuit1 bearing the filament1 attains its required strength4 ,in the following year#eia it was found that filaments composed of mixtures of oxides were far more suitable than the earlier magnesia or zirconia rods2 yttria1 thoria1 and zirconia were the chief oxides used1 small quantities of ceria being occasionally introduced4 ,with these filaments1 the increase of conductivity with temperature is far more rapid than with the pure oxides2 the preliminary heating required1 therefore1 is less and the light obtained more intense4 ,the filaments used were in the form of rods or spirals obtained by compressing the powdered oxides4 #ehi ,e4 #aidbd1 #ahig4 #eij ,e4 #bcdgj1 #ahig4 #eia ,e4 #face1 #ahih4 ,the ,nernst filaments differ markedly from those of the ordinary electric glow lamp in that they are not conductors in the ordinary sense 7or of the first order1 as ,nernst puts it7 but electrolytes1 the passage of the current being actually attended by an electro-chemical change in the filament4#eib ,the oxide is ionised2 the ions of the metals travel to the cathode or negative pole1 where the liberated atoms of metal instantly recombine with the oxygen of the air1 whilst oxygen ions travel to the anode1 from which the gas is liberated4 ,there is thus a gradual redistribution1 resulting in accumulation of oxide at the cathode with a corresponding loss at the anode1 which is balanced1 after some time1 by diffusion1 so that equilibrium is attained4 ,in consequence of this redistribution the filament glows more brightly at the anode1 where it is thinnest1 than at the cathode4 #eib ,vide ,nernst1 ,zeitsch4 ,elektrochem4 #ahii1 #f1 #da4 ,,industrial ,,applications ,,of ,,zirconium ,it has already been mentioned that zirconium received considerable attention as a suitable substance for the preparation of metallic filaments during the early stages of their development4 ,whilst at the present time this element has been abandoned for the purpose1#eic several zirconium lamps were at one time on the market1 and a brief mention of some of the work done in this direction may not be out of place4 #eic ,vide ,baumhauer1 ,zeitsch4 angew4 ,chem4 #aiaj1 #bc1 #bjfe4 ,one of the general methods for the preparation of the metallic filaments may be illustrated by a patent taken out in #aijb by ,sander1#eid for the preparation of filaments of zirconium1 with or without addition of zirconium carbide4 ,the metal1 or a compound which on heating will yield the metal and a volatile substance which can be removed1 is prepared in a finely divided condition1 and made into a paste with some organic binding material2 the paste is then forced through a tiny aperture1 and the resulting thread is shaped and heated to a high temperature in vacuo or in an inert atmosphere4 ,if an organic substance be used to form a paste with metallic zirconium1 the final process of heating results in the formation of the carbide2 the same compound is also obtained by another process protected by ,sander 7loc4 cit47 in which the hydride of zirconium1 prepared by the reduction of the oxide by means of powdered magnesium in an atmosphere of hydrogen1 is mixed with a cellulose solution1 and the liquid treated as in the manufacture of artificial silk1 the threads obtained being then heated to remove all organic matter as far as possible4 #eid ,d4 ,r4 ,p4 #accgja1 ,july1 #aijb4 ,the carbide is also probably obtained by the process of the ,british ,thomson-,houston ,company1 in which advantage is taken of the fact that zirconium oxalate is a pasty gelatinous substance1 which can be forced through a die to form a thread without addition of any agglutinating agent4 ,the oxalate1 precipitated by addition of ammonium oxalate to a solution of a zirconium salt1 is mixed with finely divided carbon1 and the threads obtained from the pasty mass heated to a very high temperature in a furnace4#eie ,zirconium oxalate is also proposed as a binding material for powdered tungsten1 in the preparation of filaments from that metal4#eif #eie ,e4 #edae1 #aijh4 #eif ,e4 #ajeij1 #aijh4 ,the compounds of zirconium and thorium with elements of group ,,vb1 according to two ,german patents1#eig are suitable for the preparation of metallic filaments in much the same way4 ,thorium1 titanium1 and zirconium are also among the metals which1 it is claimed1 can be obtained in the pure fused state by heating in an electric arc in vacuo1 so that filaments can be drawn directly4#eih #eig ,d4 ,r4 ,p4 #aecieh and #aedbii1 ,september1 #aijd4 #eih ,ibid4 #afiibh1 ,april1 #aijf4 ,metallic zirconium and its alloys have recently been employed in metallurgy4 ,the pure metal can be obtained by the calcium reduction of ,kuzel and ,wedekind 7vide p4 #caf72 zirconia is not reduced by powdered aluminium 7,goldschmidt's process71 but alloys of zirconium and iron can be easily obtained by the reduction of mixtures of the two oxides by this method4 ,alloys can be obtained containing up to #ce per cent4 of zirconium2 this ferro-zircon1 as it is called1 has been used to some extent recently in place of ferro-titanium 7vide infra7 for the purification of steels4#eii ,addition of small quantities of zirconium to steels1 brass1 copper1 etc41 is said to secure sound castings1 and to increase considerably the strength and resistance to acids of the metal4 #eii ,vide ,weiss1 ,e4 #bicgf1 #aiaj1 and ,lesmller1 ,d4 ,r4 ,p4 #bcajjb1 ,february1 #aiaa4 ,the ,technical ,uses of ,zirconia4--,since the discovery of ,baddeleyite1 the natural oxide of zirconium 7vide p4 #ge71 which occurs in large quantities in ,brazil1 many proposals have been brought forward for the employment of this compound4 ,its application to the manufacture of glasses and enamels will be referred to in the next chapter4 ,patents have been taken out protecting its use for the preparation of white pigments1#fjj as a toilet-powder1#fja and as a polishing powder1#fjb for it is extremely stable towards chemical reagents1 very voluminous1 and at the same time very hard4 ,it has long been employed for coating the lime and magnesia pencils used in the ,drummond or #8lime' light2 and recently it has been employed for the headlights of automobiles1 in the ,blriot lamp1#fjc in which a rod of zirconia is heated in a blowpipe flame fed with oil vapour and oxygen4 #fjj ,d4 ,r4 ,p4 #bcedie4 #fja ,ibid4 #bcgfbd4 #fjb ,ibid4 #bcjgeg4 #fjc ,ibid4 #agdcac1 ,september1 #aijf4 ,by far the most important property of the oxide1 from the technical point of view1 is the ease with which it resists high temperatures4 ,the natural oxide can be freed1 to a very large extent1 from the iron oxide which it encloses1 by the prolonged action of hydrochloric acid2 experiments were carried out on the material so obtained by ,simonis1#fjd who showed that by prolonged heating at a high temperature1 the remaining impurities1 chiefly ferric oxide and silica1 could be volatilised1 leaving the zirconia unchanged4 ,riecke#fje showed that whilst the oxide is very suitable for the manufacture of highly resistant crucibles1 its use is restricted by the fact that it is easily reduced by carbon at high temperatures1 forming the carbide4 #fjd ,sprechsaal1 #aijh1 #da 7#a71 #baj4 #fje ,ibid4 #bad4 ,weiss and ,lehmann have carried out exhaustive experiments on the preparation of crucibles of zirconia4#fjf ,they worked first with mixtures of zirconia and magnesia1 with phosphoric acid as a binding material2 the best results were obtained with a mixture of #ij per cent4 zirconia and #aj per cent4 magnesia1 which gave extraordinarily resistant crucibles4 ,prolonged heating at temperatures over #aijj;,c4 eliminated all the phosphoric acid by volatilisation2 the crucibles could then be heated in the blowpipe flame and plunged immediately into cold water without cracking or breaking1 and were not affected by fused sodium hydroxide or potassium hydrogen sulphate4 ,crucibles were also made with the addition of potassium and sodium salts1 and were found to answer very well2 platinum could be melted in them to a mobile liquid4 ,similar crucibles are already on the market4 #fjf ,zeitsch4 anorg4 ,chem4 #aiaj1 #fe1 #bah4 ,as early as #aijd the use of zirconia was suggested for coating muffles1 retorts1 and tubes which are required to withstand high temperatures4#fjg ,in #aijf it was proposed#fjh for the manufacture of crucibles in which rock-crystal 7quartz7 is fused for the preparation of quartz-glass1 since zirconia is not attacked by molten silica4 ,it promises to be of the greatest use in all cases where a very refractory material1 stable towards the ordinary chemical reagents1 is required4 #fjg ,pufahl1 ,d4 ,r4 ,p4 #aefgef4 #fjh ,herus ,co41 ,d4 ,r4 ,p4 #agiegj4 ,,chapter ,,xxii ,,the ,,industrial ,,applications ,,of ,,titanium ,,and ,,its ,,compounds ,though probably at least as plentiful in nature as most of the common metals1 titanium has always1 until quite recently1 been regarded as one of the rare elements4 ,of its chemistry1 very little indeed was known1 and it is improbable1 even now1 that the pure element has been isolated4 ,it had no technical value2 indeed1 its commonest ore1 ilmenite or titaniferous iron ore1 was sedulously avoided by manufacturers1 who considered that even very small percentages of the element rendered an iron ore valueless because unsuitable for working in blast furnaces4 ,towards the end of the last century1 one or two metallurgists had demonstrated that ilmenite1 under the proper working conditions1 would yield a pig iron of very good quality when smelted in the blast furnace1 but it was left for the long and arduous researches of ,kossi to show that the element is possessed of properties which render it very valuable for metallurgical purposes4 ,since the successful culmination of his work in the first few years of the present century1 titanium has attained considerable importance in the treatment of special steels for rails1 car wheels1 crushing machinery1 etc4 ,at present1 titaniferous iron ores are being worked on a large scale1 and many titanium compounds are coming into use for technical purposes4 ,the titanium minerals of commercial importance are rutile and ilmenite 7vide ,part ,i4 pp4 #eg and #gg74 ,the former1 the pure titanium dioxide1 is of fairly wide distribution1 but ilmenite occurs in far greater quantities1 forming deposits of enormous dimensions1 especially in ,america1 as1 e4g4 in ,new ,york ,co4 and ,quebec4 ,owing to its high melting-point and relatively low specific gravity1 metallic titanium can only be incorporated with molten steels with the greatest difficulty1 and for this reason alloys of titanium and iron1 known technically as ferro-titanium1 are usually employed for the treatment of steels4 ,for the preparation of ferro-titanium1 ilmenite of good quality is as suitable as rutile1 and1 of course1 far cheaper2 hence the latter is only employed for the preparation of titanium salts for use in colouring and mordanting1 and for titanium compounds for arc-lamp electrodes1 etc4 ,various processes are employed for the manufacture of ferro-titanium from ilmenite4 ,in cases in which a considerable percentage of carbon is not undesirable1 for instance1 where the alloy is required for the treatment of cast iron or of high-carbon steel1 the mineral is reduced directly with carbon in an electric furnace2 the ferro-titanium so obtained usually contains from six to eight per cent4 of carbon4 ,for pure iron-titanium alloys1 the process worked out by ,rossi#fji is used in ,america almost entirely4 ,ilmenite is charged into a bath of molten aluminium1 heated electrically2 the mineral is at once attacked1 with formation of iron1 in which the titanium dissolves as reduction proceeds4 ,this process may also be used for reduction of rutile1 if scrap iron is added to the aluminium bath1 to allow of the formation of the required alloy4 ,in ,germany1 the ,goldschmidt or #8thermite' reaction is largely employed2 powdered ilmenite is intimately mixed with the calculated quantity of aluminium powder1 reduction being started as usual by means of a fuse of magnesium ribbon imbedded in a small quantity of barium peroxide4 #fji ,elect4 chem4 ,ind4 #aijc1 #a1 #ebc4 ,quite recently1 the question of the separation of titanium compounds from ilmenite used for the manufacture of pig iron has attracted considerable attention4 ,it has been already mentioned 7vide supra7 that titaniferous iron ores have been shown to be perfectly amenable to blast-furnace treatment1 the old and deeply rooted idea that titanium-bearing slags are stiff and troublesome being entirely contrary to facts1 when suitable conditions are observed2#faj moreover1 it is shown that the pig iron obtained is of unusually good quality4 ,rossi has suggested#faa that if sufficient carbon be added to reduce all the silica and oxides of iron1 with enough lime to slag off the titanium dioxide as calcium titanate1 the latter can be used as a source of titanium compounds or alloys1 whilst a ferro-silicon will be obtained as pig metal2 the temperature must be carefully adjusted to ensure reduction of the silica without loss of titanium dioxide4 ,another patent#fab proposes the reduction of the ore in an electric furnace1 and the treatment of the crude ferro-titanium in a converter with a blast of air or nitrogen2 the titanium nitride formed is then driven out of the metal by a blast of superheated steam--any ammonia or cyanogen formed being collected--and removed1 the iron remaining being #8,bessemerised' directly in the same converter2 the titanium nitride can be used as a manure1 or for the manufacture of ammonia or nitric acid 7vide infra74 ,the removal of iron as the volatile carbonyl has also been suggested1#fac the titanium being subsequently transformed into the nitride4 #faj ,vide1 e4g4 ,iron ,age1 #aiji1 #hd1 #aadi and #abbc4 #faa ,e4 #cehb1 #aija4 #fab ,sinding-,larsen and ,willumsen1 ,d4 ,r4 ,p4 #bbjedd1 ,april1 #aiaj4 #fac ,sinding-,larsen1 ,e4 #agfcb1 #aiaj4 ,employment of the ,element in ,metallurgy4--,it has been already mentioned that titanium itself is quite unsuitable for direct incorporation with steel4 ,besides the relatively low specific gravity 7#eb71 which would render mixing very difficult1 the very high melting-point 7given by ,weiss and ,kayser#fad as #bcej7 would prevent uniform dissemination4 ,the element is therefore generally used in the form of a ferro-titanium of low titanium content1 #aj-ae per cent4 being the proportion usually employed4 ,the addition should be made at the end of the ,bessemer process1 and after the addition of the required quantities of manganese and silicon alloys2 the calculated quantity of ferro-titanium is added as the steel runs from the converter into the ladle4 ,a suitable proportion is said to be one-half per cent4 of alloy1 so that the actual proportion of titanium to steel is somewhere about #ae-ah lb4 per ton4 ,six or eight minutes should be allowed after the addition1 for the titaniferous slag to come to the surface4 #fad ,zeitsch4 anorg4 ,chem4 #aiaj1 #fe1 #cde4 ,although low percentage ferro-titanium is usually employed1 it has been stated that high-percentage alloys1 and even the element itself1 are immediately taken up by steel if aluminium be added at the same time4 ,thus ,venator#fae states that if titanium and aluminium be added together to the bath1 both elements are immediately taken up1 the reaction being very rapid and complete2 the effects produced by the titanium are in no way influenced by the presence of the aluminium4 ,goldschmidt#faf proposes the use of ferro-titanium containing #bd-be per cent4 of the element1 with #c per cent4 of aluminium2 this dissolves very readily1 is very effective1 and moreover1 can be very easily prepared by the alumino-thermic reaction4 #fae ,stahl ,eisen1 #aiaj1 #cj1 #fej4 #faf ,d4 ,r4 ,p4 #bcedfa1 ,june1 #aiaa4 ,in some cases1 where it is desired to treat a steel both with silicon and with titanium1 ferro-alloys containing both of these elements may be employed4 ,by reduction of ilmenite or rutile with carbon in an electric furnace1 in presence of silica1 ,becket#fag obtains alloys of high titanium and silicon content1 which are said to dissolve very easily in molten steels and to produce improved effects4 ,the ,titanium ,alloy ,manufacturing ,company have also patented#fah the preparation of titanium-silicon alloys1 with or without addition of iron or copper1 by the reduction of a mixture of rutile and quartz4 #fag ,u4 ,s4 ,p4 #idjffe and #idaeec of ,november1 #aiji4 #fah ,f4 #djgheh1 ,january1 #aiaj4 ,recently the use of ferro-titanium in the manufacture of pig iron has attracted attention4 ,for this purpose1 alloys of very low titanium-content 7#ja-aj per cent47 are employed4 ,addition of very small amounts of such alloys to the molten metal before casting is said to have a marked cleansing effect1#fai resulting in much better and stronger castings4 #fai ,vide ,slocum1 ,chem4 ,eng4 #aiaa1 #ac1 #beg4 ,whilst it is very generally agreed that the addition of titanium results in the production of much stronger and more durable products1 the question of the precise effect obtained is by no means definitely settled4 ,the experimental work1 whilst pointing on the whole to the superiority of titanium-treated steel1 is by no means conclusive2 in some cases1 indeed1 it is conflicting4 ,thus the micro-photographs obtained by von ,maltitz#fbj and ,venator#fba show that the titanium-treated steel has a far cleaner fracture and far more homogeneous structure than steels not so treated2 on the other hand1 the micro-photographs of ,treuheit#fbb show practically no improvement in structure for the titanium steel4 ,the exhaustive tests of the first two authors1 again1 and the experiments of numerous railways in the use of titanium steel rails1#fbc demonstrate clearly that the treatment results in improvement in strength and durability of the product2 but the work of ,otto#fbd proves equally clearly that his products did not differ markedly1 whether titanium-treated or not1 and he is of opinion that the rail tests were not sufficiently prolonged or searching to be considered conclusive4 ,it is nevertheless to be considered certain that the use of titanium does cause a marked improvement in the quality of the steels obtained1 and especially in the durability of rails4 ,the negative results obtained by some authors may be explained1 firstly1 on the ground that no tests are conclusive unless carried out with steel from the one bath1 one half of which has been treated with titanium1 and the other half not so treated2 secondly1 that the ferro-titanium must be incorporated with the metal1 and must not be suffered to be taken up by the slag1 and so lost2 and thirdly1 that the bath must be allowed to remain for some minutes after treatment1 in order that the reaction may be complete1 and the titanium-bearing slag allowed to rise to the surface4 ,when these conditions are carefully observed1 experiment shows that marked improvement in the quality of the steels produced is effected4 #fbj ,stahl ,eisen1 #aiaj1 #bi1 #aeic4 #fba ,ibid4 #aiaj1 #cj1 #fej4 #fbb ,ibid4 #aiaj1 #cj1 #aaib4 #fbc ,vide ,dudley1 ,j4 ,ind4 ,eng4 ,chem4 #aiaj1 #b1 #bii2 also ,cass4 ,mag4 #aiaa1 #dj1 #dhc4 #fbd ,vide abstract in ,stahl ,eisen1 #aiab1 #cb1 #adig4 ,as to the actual nature of the effect produced1 it is generally believed that titanium acts merely as a cleansing agent1 freeing the metal from occluded or combined gases1 and removing blow-holes1 so producing a denser and more homogeneous structure1 with consequent improvement in properties4 ,the added titanium is usually found entirely in the slag1 so that it appears certain that it does not alloy1 but merely purifies4 ,it certainly acts as a powerful and rapid deoxidiser1 removing the last traces of the gas which have escaped the action of the manganese1 silicon1 etc41 with which steels are now generally treated4 ,many authorities1 on the ground of analyses1 and of the known affinity of titanium for nitrogen1 believe that it very largely reduces the nitrogen-content1#fbe which is so harmful2 this1 however1 is still an open question4#fbf ,it is stated that if excess of titanium is used1 so that small quantities--#jje-jbj per cent4--remain in the finished steel1 the toughness and durability are further increased2#fbg but as a rule1 manufacturers prefer to work with smaller quantities1 so that no free titanium remains in the product4 #fbe ,vide von ,maltitz1 loc4 cit4 #fbf ,vide ,venator1 loc4 cit4 #fbg ,vide ,bull4 ,imp4 ,inst4 #aiaa1 #i1 #acd4 99 99 99 99 99 ,the preparation of alloys of titanium with almost all the commoner metals is protected by patent1 but few of these are of technical importance4 ,small quantities of titanium are said to improve very considerably the properties of copper and its alloys1 the brasses1 bronzes1 etc41 especially in castings4 ,the addition is usually made in the form of an appropriate titanium alloy1 prepared by reduction of the mixed oxides with carbon in an electric furnace1 or treatment of the mixed oxides1 together with the alloying metal1 with aluminium under similar conditions4#fbh ,the titanium-silver alloys obtained in this way#fbi are said to improve greatly the structure of silver1 by preventing the familiar #8spitting' as the fused metal cools4 #fbh ,vide ,rossi1 ,u4 ,s4 ,p4 #ihfeje1 ,march1 #aiaa2 #icehfc1 ,october1 #aiji1 etc4 #fbi ,rossi1 ,u4 ,s4 ,p4 #ajbddgf and #ajbedbf1 ,august1 #aiab4 ,an interesting process1 which has been patented by ,rossi1#fcj recalls the method of formation of cementation steels4 ,he has found that if a metal be loosely covered with its alloy with titanium1 in a finely powdered condition1 and the whole heated1 the titanium diffuses into the metal1 to a depth and concentration which vary with the temperature and the time of heating4 ,he suggests that in this way a metallic body may be toughened and strengthened at any desired point1 e4g4 steel for armour-plate at the surface4 ,whether the process will be of any technical value or not can only be shown by experiment4 #fcj ,u4 ,s4 ,p4 #ihfejd1 ,march1 #aiaa4 ,application to ,arc-lamp ,electrodes4--,during the last fifteen years1 innumerable efforts have been made to adapt titanium and its compounds to the manufacture of arc-lamp electrodes1 or pencils4#fca ,the spark-spectrum of titanium is very rich in lines1 and in respect of light efficiency1 the element is very suitable for the purpose2 the experimental difficulties1 however1 have been very great1 and though electrodes containing titanium compounds have been on the market for some years1 the problem cannot be said to have been satisfactorily solved4 ,the best pencils contain titanium carbide1 but successful attempts have been made to use the oxide4 ,as early as #aijd1 ,weedon#fcb proposed an electrode prepared by heating #g parts 7#a mol47 of the dioxide with #a part of carbon to #aejj-bjjj;,c42 the #8sub-oxide' produced was powdered1 worked up into a paste with a suitable binding material1 and forced through a nozzle4 ,the sticks so obtained1 after drying and baking in the usual manner1 were said to give satisfactory results1 but consumption is very rapid1 and troublesome deposits of the dioxide are formed at the end of the electrode4 ,the dioxide1 which alone is a very bad conductor1 enters directly into the composition of the so-called #8magnetite' pencils1 which are best made#fcc by fusing together magnetite1 rutile1 and chromite1 in suitable proportions1 with a little potassium fluoride1 powdering the brittle mass1 and using this to form a paste from which the pencils may be obtained as usual4 ,these electrodes are said to give a very efficient and fairly steady arc4 ,they have the disadvantage that tiny glowing particles are thrown off1 which soon render the globes opaque2 the addition of sulphur#fcd to the powder during manufacture is said greatly to diminish this inconvenience4 ,pencils made in a similar manner from powdered ferro-titanium#fce do not appear to have come into use4 #fca ,vide1 e4g4 ,ladoff1 ,j4 ,ind4 ,eng4 ,chem4 #aiji1 #a1 #gaa4 #fcb ,e4 #bfiba1 #aijd4 #fcc ,e4 #bjbg1 #aiji4 #fcd ,e4 #ahife1 #aiji4 #fce ,u4 ,s4 ,p4 #hdjfcd1 ,january1 #aijg4 ,the carbide alone is a good conductor1 and gives a very satisfactory light1#fcf but electrodes made from this compound without additions have several disadvantages4 ,the life is short1 and the arc soon becomes flickering and unsteady4 ,a deposit of the badly conducting dioxide gradually accumulates on the anode1 and once the current has been interrupted1 this deposit renders it very difficult to strike the arc again4 ,these disadvantages are largely overcome by a series of improvements recently patented in ,germany by the ,allgemeine ,elektrizitts ,gesellschaft of ,berlin4 ,addition of small quantities--#de per cent4--of chromium carbide increases the length of life2#fcg the unsteadiness and flickering are greatly diminished by incorporation of powdered coke1 cryolite and fluorspar1#fch or better1 of the titanofluoride of calcium or cerium1#fci whilst the addition of finely divided sulphur 7or selenium or tellurium7#fdj greatly reduces the disadvantage due to the throwing off of incandescent particles4 ,the ,british ,thomson-,houston ,company patents a similar electrode1#fda in which a carbon-mixture is used instead of coke1 and the electrode is manufactured with a carbon shell4 ,for this purpose1 the paste prepared from the powdered mixture may be filled into a hollow carbon rod1 or the lightly baked pencil may be coated with pitch and heated to a high temperature4 ,the use of a mixture of cerium fluoride and tungstate1 with carbon and cryolite1 is also said to prevent flickering4#fdb #fcf ,weedon1 ,trans4 ,amer4 ,el4 chem4 ,soc4 #aiaa1 #af1 #bag4 #fcg ,d4 ,r4 ,p4 #bcabca1 ,february1 #aiaa4 #fch ,ibid4 #bccabe1 ,march1 #aiaa4 #fci ,ibid4 #beahcg1 ,october1 #aiab4 #fdj ,ibid4 #bcddff1 ,may1 #aiaa4 #fda ,e4 #fejj1 #aiab4 #fdb ,guay1 ,u4 ,s4 ,p4 #ajciebb1 ,september1 #aiab4 ,in arc lamps in which pencils containing titanium compounds are used1 the anode is generally made of copper1 and is placed below the cathode1 the reverse being the case where carbon electrodes are employed4 ,the copper is inactive1 and contributes nothing to the light2 if the anode be of suitable dimensions1 it wears away very slowly1 whereas the cathode1 containing the titanium compound1 is rapidly consumed4 ,in lamps in which carbon electrodes are used1 the light is emitted chiefly from the extremities of the electrodes1 the path of the arc being comparatively non-luminous2 the light has the familiar reddish-yellow colour characteristic of the earlier forms of arc lamps4 ,where titanium pencils are employed1 however1 the light is emitted almost entirely from the arc itself1 the electrodes contributing very little1 and is of a pure white colour1 very different from that of the carbon lamp4 ,attempts have been made to employ titanium in the manufacture of metal filaments for glow lamps4 ,the metal would be very suitable for this purpose1 by reason of its high melting-point and low conductivity1 but the difficulty of obtaining it in the pure state1 and the remarkable susceptibility of the filament to traces of impurity1 have so far proved insuperable4 ,for the sake of illustration1 a proposal put forward in #aijh may be briefly referred to4#fdc ,pure titanium dioxide is heated in a stream of ammonia2 the nitride obtained is decomposed at #abjj in vacuo1 and after cooling1 the metal is powdered and made into a paste with a solution of albumen in ammonia4 ,the threads obtained from this in the usual manner are heated to #abjj in an electric furnace2 the carbon deposited from the albumen forms the cyanide by reaction with the trace of nitride which has escaped decomposition1 or which has been formed by further action of ammonia4 ,the cyanide is volatile1 and can be removed at high temperatures in vacuo1 leaving a sintered filament of the metal4 ,so susceptible is the filament to impurity1 that the trace of carbon deposited from the vapour of the oil of the pump which diffuses into the vacuum is sufficient to render it so fragile as to be useless4#fdd #fdc ,trenzen and ,pope1 ,e4 #adheb1 #aijh4 #fdd ,vide ,bull4 ,imp4 ,inst4 #aiaa1 #i1 #acd4 ,titanium ,compounds in ,dyeing and ,colouring4--,the use of titanium compounds as mordants in the dyeing of leather and textile goods has been known for a considerable time4#fde ,as early as #ahif1 a patent was taken out by ,barnes#fdf for the treatment of prepared animal skins by immersion in a bath of a titanium salt4 ,subsequent boiling or steaming causes hydrolysis1 with precipitation in the skin of hydrated titanium dioxide1 which forms lasting dye-lakes when the fabric is immersed in the dye-bath4 ,whilst this treatment has been found satisfactory with some classes of leather goods1#fdg more delicate kinds are liable to be injured by the mineral acid set free1 and numerous patents protecting the preparation and employment of organic salts of the element have been taken out by ,dreher4#fdh ,the same investigator#fdi has discovered that excellent results can be obtained in the cold by the addition of various #8,hlfsalze1' which are chiefly acetates or formates of the alkaline earth metals1 chromium1 or aluminium1 or basic salts of the last two4 ,double decomposition of these with the titanium salt forms basic or highly hydrolysed salts of the latter1 so that the hydrated oxide or a basic compound is formed on the fabric4 #fde ,a good account of some of the earlier work in this connection is given by ,erban1 ,chem4 ,zeitg4 #aijf1 #cj1 #ade4 #fdf ,e4 #egab1 #ahif4 #fdg ,vide ,dreher1 ,d4 ,r4 ,p4 #adbdfd1 ,june1 #aijc4 #fdh ,vide ,e4 #bbfbi and #bcahh of #aija1 #adiba and #bgeig of #aijb1 and #ebaa of #aijc4 #fdi ,vide ,d4 ,r4 ,p4 #acijei and #acijfj of ,february1 #aijc1 and #acihch of ,march1 #aijc4 ,the titanium salts specified in these patents are salts of the element in the tetravalent condition1 prepared from rutile by the action of strong mineral acids4 ,as early as #aijb1 the technical preparation of salts of trivalent titanium for reducing purposes was patented by ,spence and ,spence1 of ,manchester4#fej ,the process is an electrolytic one1 and is effected in a cell divided into two compartments by a porous partition1 one electrode being introduced into each compartment2 an electromotive force of #c-d volts is required4 ,a #bj-be per cent4 titanium tetrachloride solution is introduced into the cathode compartment1 and dilute hydrochloric acid into the anode compartment2 on electrolysing1 chlorine is evolved at the anode1 and may be utilised as usual in the preparation of bleaching powder1 etc41 whilst the tetrachloride in the cathode compartment is reduced to trichloride4 ,the solution is then concentrated at #fe-gj;,c4 under reduced pressure1 and the crystalline trichloride separated4 ,in the preparation of the corresponding sulphate1 sodium sulphate must be present in the cathode compartment1 and a double salt is obtained2 the process is carried out in lead-lined cells1 in presence of excess of sulphuric acid4 ,the preparation of the sesquioxide1 ,ti,o1 free from compounds of aluminium and iron1 was also suggested by ,dreher#fea by reduction of the acid solution of the impure or mixed salts with zinc or sodium amalgam1 and approximate neutralisation2 the sesquioxide differs from the dioxide in that it separates while the solution is still somewhat acid1 which the hydrated oxides of iron and aluminium will not do4 ,dreher suggested that the strong reducing properties of the sesquioxide and its salts should make these valuable for bleaching1 colour-printing1 and similar purposes4 #fej ,e4 #afbch and #ahajh of #aijb4 #fea ,e4 #ahce1 #aijc4 ,more recently#feb the reduction of titanium salts by means of aluminium powder has been suggested2 in the case of the sulphate1 the aluminium salt formed may be partly eliminated as alum1 in the ordinary way1 if desired1 but it is claimed that its effect is beneficial rather than harmful4 ,the preparation of organic double basic salts of trivalent titanium1#fec which hydrolyse very readily1 suggested the use of such compounds as mordants and for reducing purposes4 ,these salts may be prepared fairly easily#fed by adding concentrated solutions of the appropriate potassium1 sodium1 or ammonium salts in excess to concentrated solutions of the trichloride1 in absence of air4 ,the double salts separate1 and are washed and dried2 in this condition they are fairly stable1 but the solutions hydrolyse at once on merely warming1 with separation of the hydrated sesquioxide4 ,on this account1 and also because of the strong reducing action1 these compounds are likely to prove valuable as mordants1 and for other purposes4 #feb ,spence1 ,craig1 and ,spence1 ,e4 #acbfj1 #aiaa4 #fec ,sthler and ,bachran1 ,ber4 #aiaa1 #dd1 #biab4 #fed ,kunheim and ,co4 and ,sthler1 ,d4 ,r4 ,p4 #bhdbea1 ,june1 #aiab4 ,titanium compounds have frequently been suggested for the preparation of colouring-matters2 the ferrocyanide has a fine green colour1 and is used to some extent in place of arsenical pigments for the preparation of coloured wall-papers1 whilst the dioxide is of some value for tinting artificial teeth1 porcelain tiles1 etc4 ,yellow and reddish-yellow pigments are produced from rutile and ilmenite by various methods4 ,a fine covering paint is said to be obtained by a process#fee in which ilmenite is powdered and roasted to #ejj;,c42 the cooled product is crushed with water1 and after one or two washings to remove soluble compounds1 yields a very finely divided orange-yellow suspension1 the precise shade of which varies with the duration and temperature of the roasting4 ,the product is at once thrown down from the suspension1 by addition of a small quantity of a salt solution1 and so can easily be obtained in the solid state4 ,in another process1#fef the pulverised ilmenite is warmed with concentrated sulphuric acid1 in which it dissolves with great development of heat2 the excess of acid is removed by evaporation and the mass calcined to decompose the sulphates4 ,it is stated that different shades may be obtained by carrying out the last operation in an atmosphere of sulphur dioxide or other gas4 #fee ,farup1 ,e4 #cfdi1 #aiaj2 ,f4 #dabefc1 ,may1 #aiaj4 #fef ,e4 #ajcfh1 #aiaa4 ,in connection with the colouring properties of the oxides of titanium1 it is interesting to note that the blue colour of sapphires is probably due to the presence of compounds of trivalent titanium2 ,verneuil#feg has succeeded in preparing artificial sapphires in all respects identical with the natural stones by fusing alumina with small quantities of titanium dioxide and ferric oxide in the flame of the oxyhydrogen blowpipe1 which effects the reduction4 #feg ,compt4 rend4 #aiaj1 #aej1 #ahe4 ,other ,uses of ,titanium ,compounds4--,owing to the high price of the tin dioxide which is largely employed for the preparation of enamels and opaque glasses1 innumerable suggestions have been made for the employment of the oxides of titanium and zirconium in this direction4#feh ,a critical examination of the question has been made by ,grnwald2#fei he finds that the opacity consequent on addition of these compounds increases with the amount of clay used1 within limits1 and concludes that the effect is due to displacement of alumina by the oxides1 with formation of silicates of titanium and zirconium1 which dissolve in the melt4 ,he states that the results obtained from the use of these oxides are not comparable with those given when stannic oxide is employed1 and that therefore the former oxides are of little use for this purpose4 #feh ,vide1 e4g4 ,d4 ,r4 ,p4 #ahicfd1 #bahcaf1 #aaejaf1 #bjgjja2 ,f4 #dchijh1 etc4 #fei ,sprechsaal1 #aiaa1 #dd1 #gb4 ,these two oxides find employment to a small extent in the manufacture of #8,siloxide' quartz glass4#ffj ,quantities up to #ae per cent41 added to the molten silica1 reduce the difficulty of working the material4 ,exhaustive tests carried out by ,thomas#ffa indicate that the vessels made from this material are1 on the whole1 to be preferred to ordinary quartz glass1 resisting high temperature better1 and showing less tendency to become crystalline and therefore brittle when maintained for considerable times at high temperature4 #ffj ,wolf-,burckhardt and ,borchers1 ,f4 #dcbghf1 ,october1 #aiaa4 #ffa ,chem4 ,zeitg4 #aiab1 #hf1 #be4 99 99 99 99 99 ,much work has been carried out during the last few years with the object of utilising titanium compounds for the #8fixation' of nitrogen4 ,the metal combines very vigorously with the gas at about #hjj;,c4 7vide p4 #bbd71 forming the nitride4 ,if the gas1 or air1 be passed over a heated mixture of the dioxide with powdered coke1 formation of the cyanonitride occurs at comparatively low temperatures 7#aajj-acjj;,c47 if a small quantity of an alkali salt be present1#ffb the action being apparently catalytic2 if excess of carbon is used1 considerable quantities of the cyanide may be formed4 ,numerous experiments carried out by the chemists of the ,badische ,anilin- und ,soda-,fabrik have shown that at high temperatures1 the action of water and a suitable oxidising agent1 or in the presence of metallic compounds1 the action of steam alone1 will liberate considerable quantities of ammonia from both these derivatives1#ffc whilst in the presence of platinum compounds1 if air be pumped in1 the higher oxides of nitrogen are formed4 ,one or two examples may be given3 7#a7 ,ti,n #d,na,o,h ,h,o #b;,cu,o #b,,nh ,cu,o #b,na,ti,o--autoclave at #ahj;,c4 7#b7 #b,ti,n #b;,h,,so #f;,h,o ,o #d,ti,o #b7,,nh7,,so--autoclave at #abj-adj;,c4 7#c7 ,ti,n #c;,h,o ,ti,o #b,,nh--steam at #ejj-fjj;,c4 #ffb ,vide ,bosch1 ,u4 ,s4 ,p4 #ieghdb1 ,may1 #aiaj4 #ffc ,vide1 e4g4 ,d4 ,r4 ,p4 #bjbefc and #bjcgdh of ,march1 #aijg2 #bjdbjd and #bjddge of ,november1 #aijh2 ,e4 #bdad1 #aijh2 ,f4 #chgjjb of ,june1 #aijh2 ,u4 ,s4 ,p4 #ieghdc of ,may1 #aiaj1 gives a rsum of all the processes4 ,in the second case1 the oxygen is derived from air pumped into the apparatus1 and ferrous sulphate is used as a catalyst4 ,in the third case1 a metallic salt1 oxide1 or hydroxide is required as a catalyst4 ,in view of the success of the cyanamide method for the fixation of atmospheric nitrogen1 these processes1 though of considerable theoretical interest1 do not seem likely to become of practical importance4 99 99 99 99 99 ,one or two minor uses have been suggested for titanium dioxide4 ,small quantities are fused with bauxite1 silica1 and ferric oxide in the preparation of abrasives1#ffd whilst a mixture with carbon is suggested as a refractory body for linings1 crucibles1 etc41 surface heating of this forming a layer of highly resistant carbide4#ffe ,an interesting ,american patent protects the use of the dioxide for the preparation of phosphorus pentoxide from bone-ash or natural calcium phosphate4#fff ,the pulverised mixture of the phosphate and oxide is introduced at the upper end of an inclined rotating furnace1 by means of a hopper and screw feed2 fuel is fed in at the lower end1 and an outlet is provided for the periodic removal of the calcium titanate1 etc41 formed4 ,the silica and alumina of the impure phosphate1 together with the titanium dioxide introduced1 displace the phosphorus pentoxide1 which1 being volatile1 escapes continuously through a special pipe2 there is left a mixture of silicate1 aluminate and titanate of calcium1 which may be used as a source of titanium compounds4 #ffd ,saunders1 ,u4 ,s4 ,p4 #iedgff1 #iedggg1 and #iedggh4 #ffe ,becket1 ,u4 ,s4 ,p4 #ajchhbg1 ,september1 #aiab4 #fff ,peacock1 ,u4 ,s4 ,p4 #iiehig1 ,june1 #aiaa4 ,estimation of the ,element4--,owing to the difficulties of the separation from the acidic oxides1 silica1 zirconia1 and the pentoxides of columbium and tantalum1 and from the basic oxides1 alumina and the oxides of iron and tin1 the estimation of titanium in a mineral or a steel is usually a difficult and tedious process4 ,gravimetric as well as volumetric methods are employed4 ,in the former1 the element is isolated and weighed in the form of the dioxide2 in the latter1 standard solutions of suitable oxidising agents are employed1 advantage being taken of the ease with which the element can be transformed from the trivalent to the tetravalent condition4 ,the mineral or steel in which the element is to be estimated is usually fused with sodium hydrogen sulphate1 which forms the sulphate4 ,if thorium1 uranium or rare earths are present1 treatment in the cold with hydrofluoric acid is often more suitable2 the acidic oxides are taken into solution1 leaving the more positive elements in the form of the insoluble fluorides4 ,trautmann finds that steels or ferro-titaniums of high silicon content are attacked only very slightly by fused sodium bisulphate2 he recommends#ffg ignition to the oxides1 evaporation with hydrofluoric acid to remove silicon as the volatile tetrafluoride1 and fusion of the residue with bisulphate4 #ffg ,zeitsch4 angew4 ,chem4 #aiaa1 #bd1 #hgg4 ,the bisulphate melt1 after cooling1 is leached with water1 and the whole boiled under a reflux condenser for several hours2 this treatment should throw down the oxides of titanium1 columbium and tantalum1 leaving zirconium and aluminium in the form of the sulphates in the acid solution2 the addition of ammonia may be necessary to effect complete hydrolysis4 ,the acidic oxides may also be precipitated if the solution be diluted and treated with excess of acetic acid before boiling4 ,in both cases1 a considerable quantity of iron is thrown down4 ,the precipitated oxides are dissolved in the cold by dilute sulphuric acid to which hydrogen peroxide has been added4 ,for volumetric estimation1 separation from iron is not generally necessary4 ,if gravimetric methods are to be employed1 separation may be effected in several ways4 ,titanium dioxide may be precipitated in a fairly pure condition by reducing the solution with sulphur dioxide1 and boiling until the titanium sulphate has been completely hydrolysed4 ,according to ,barneby and ,isham1#ffh this method gives low results2 these authors prefer to remove iron completely from the solution1 and then effect complete hydrolysis by addition of ammonium acetate and acetic acid to the boiling solution4 ,for this purpose1 they dissolve the mixed oxides in hydrochloric acid1 and remove ferric chloride by ether extraction4 ,bornemann and ,schirmeister#ffi precipitate titanium dioxide completely by means of ammonia1 holding iron in solution as ferrocyanide2 for this purpose1 iron is completely reduced to the ferrous state by means of sodium hydrogen sulphite1 and solutions of potassium cyanide and ammonia are added together to the warm liquid1 which is afterwards heated nearly to the boiling-point to effect the precipitation4 #ffh ,j4 ,amer4 ,chem4 ,soc4 #aiaj1 #cb1 #ieg4 #ffi ,metallurgie1 #aiaj1 #g1 #gbc4 ,iron may also be removed by the ordinary methods1 if some reagent be previously added to hold titanium in solution4 ,for this purpose1 tartaric acid and its salts are commonly used2 none of the ordinary precipitants will throw down the element if this reagent be present4 ,after addition of ammonium tartrate1 iron is removed by means of ammonium sulphide4 ,after filtering1 tartaric acid may be removed by means of potassium permanganate1 the manganese dioxide formed being reduced with sulphur dioxide4 ,according to ,thornton1#fgj evaporation with a mixture of sulphuric and nitric acids is a more convenient method of destroying the organic acid2 titanium dioxide is then thrown down by diluting and boiling in the usual way4 #fgj ,amer4 ,j4 ,sci4 iv41 #aiab1 #cd1 #bad4 ,bourion#fga describes a method of separating the oxides by the action of a mixture of hydrogen chloride and sulphur monochloride at a suitable temperature4 ,the ferric chloride which is formed sublimes1 leaving titanium dioxide unattacked4 #fga ,compt4 rend4 #aiab1 #aed1 #abbi4 ,for volumetric estimation of small quantities of titanium in solution1 colorimetric methods are generally employed4 ,addition of hydrogen peroxide to such a solution gives an intense reddish-yellow colouration1 which is compared with the colourations obtained with solutions containing known quantities of the element4 ,wells#fgb finds that under suitable conditions1 an accuracy of about #b per cent4 is to be expected with this method4 ,lehner and ,crawford#fgc find that in concentrated sulphuric acid solution1 thymol gives a red colouration which is at least twenty-five times as intense as the colour given by hydrogen peroxide1 and they accordingly propose thymol as a suitable reagent for the colorimetric estimation4 ,fenton#fgd has shown that a very intense colouration is obtained when a solution of a titanium salt is treated with dihydroxymaleic acid2 this reaction has been shown by ,mellor#fge to be well adapted for the colorimetric estimation and for the estimation of titanium and vanadium together in a solution4 #fgb ,zeitsch4 anorg4 ,chem4 #aiaa1 #gj1 #cie4 #fgc ,j4 ,soc4 ,chem4 ,ind4 #aiab1 #ca1 #ief4 #fgd ,trans4 ,chem4 ,soc4 #aijh1 #ic1 #ajfd4 #fge ,abstr4 ,chem4 ,soc4 #aiac1 #ajd1 ii4 #fbg4 ,the volumetric methods for the estimation of larger quantities require complete reduction to the trivalent condition4 ,this is best effected by means of zinc and hydrochloric acid1 or1 where potassium permanganate is to be used1 by zinc and sulphuric acid4 ,precautions must be taken to ensure that reduction is complete2 an apparatus suitable for rapid estimations has recently been described by ,shimer and ,shimer4#fgf ,where potassium permanganate is employed 7,pisani's method71 the iron must be estimated separately by means of a standard solution of titanium trichloride4 ,knecht and ,hibbert#fgg titrate directly1 after reduction1 with a standard solution of a ferric salt1 using potassium thiocyanate as indicator2 here no correction has to be applied for iron originally present in the solution4 ,the same advantage attaches also to the method of titration by means of methylene blue1#fgh a dye reduced to the colourless leuco-base by salts of trivalent titanium1 but not affected by ferrous salts4 #fgf ,j4 ,soc4 ,chem4 ,ind4 #aiab1 #ca1 #iee4 #fgg ,ber4 #aijc1 #cf1 #aedi4 #fgh ,see ,hibbert1 ,j4 ,soc4 ,chem4 ,ind4 #aiji1 #bh1 #aij4 ,,index ,absorption ,spectra1 #adh ,acetate process1 #cjd ,acetylacetone derivatives1 #ace ,actinium1 #ajj ,aenigmatite1 #h1 #ee ,aeschynite1 #h1 #fe ,aldebaranium1 #bje ,allanite1 #h1 #cf1 #ci1 #ia ,alshedite1 #ed ,alvite1 #h1 #ei ,anatase1 #h1 #gh ,ancylite1 #h1 #ha ,anderbergite1 #h1 #di ,annerdite1 #i1 #fa ,arc spectra1 #aea ,arfvedsonite1 #i1 #ea ,arizonite1 #i1 #ei ,arrhenite1 #i1 #gj ,astrophyllite1 #i1 #ee ,auer mantles1 history of1 #bgj ,auerbachite1 #i1 #ca ,auerlite1 #i1 #ea ,baddeleyite1 #aj1 #ge ,bagrationite1 #aj1 #de ,bastnsite1 #aj1 #ha ,beckelite1 #aj1 #ea ,benitoite1 #aj1 #ee ,beryl1 #ajb ,blomstrandine1 #aj1 #fh ,blomstrandite1 #aj1 #ga ,bodenite1 #aa1 #db1 #de ,bragite1 #fc ,brasilite1 #gf ,britholite1 #aa1 #ea ,brggerite1 #aa1 #gc ,brookite1 #aa1 #gi ,bucklandite1 #db ,calciothorite1 #aa1 #di ,calcite1 #b1 #ch ,cappelenite1 #aa1 #ea ,carbides of rare earth group1 #abj ,carbonates of rare earth group1 #acj ,caryocerite1 #ab1 #ea ,cassiopeium1 #bje ,cassiterite1 #c1 #de1 #df1 #gg ,castelnaudite1 #ab1 #hh ,cataplejite1 #ab1 #ea ,cathode luminescence1 #aea ,celtium1 #bjg ,ceria1 #aaa1 #aag1 #aah1 #afa ,ceric compounds1 #afj ,cerite1 #a1 #cj ,cerium1 atomic weight of1 #afd compounds1 applications of1 #cag detection 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,eucolyte-,titanite1 #ed ,eucrasite1 #ae1 #di ,eudialite1 #ae1 #ej ,europium1 atomic weight of1 #ahh compounds of1 #ahh history of1 #ahe ,euxenite1 #ae1 #ff1 #fh ,eytlandite1 #fj ,fahnehjelm mantles1 #bfi ,fergusonite1 #ae1 #ch1 #fc1 #ij ,ferrocyanides of rare earth group1 #abc ,ferro-titanium1 #cbf ,florencite1 #ae1 #ea ,fluocerite1 #ae1 #hi ,fluorides of rare earth group1 #abj ,fluorspar1 #b1 #hi1 #ajb ,formates of rare earth group1 #acc ,freyalite1 #af1 #di ,gadolinite1 #a1 #af1 #cc1 #ia ,gadolinium1 atomic weight of1 #aij compounds of1 #aij detection of1 #aia history of1 #ahd1 #ahi ,geikielite1 #af1 #ei ,gorceixite1 #af1 #hh ,greenovite1 #ed ,grthite1 #bf1 #ed ,guarinite1 #af1 #ea ,gummite1 #gc ,hainite1 #af1 #gj ,halogen oxy-salts of rare earth group1 #abc ,harmatite1 #aj1 #ha ,helium ratio1 #ajd1 #ajf ,hellandite1 #af1 #db ,hiortdahlite1 #ag1 #ea ,hjelmite1 #ag1 #fd ,holmium1 compounds of1 #bja history of1 #aie separation of1 #aif ,homilite1 #ag1 #ea ,hussakite1 #ag1 #hg ,hydrides of rare earth groups1 #aaf ,hydrotitanite1 #ag1 #ei ,hydroxides of rare earth groups1 #aaf ,illuminating power of gas1 #bff of mantles1 #bid ,ilmenite1 #ag1 #eg1 #ij ,ilmenorutile1 #ag1 #ga ,johnstrupite1 #ag1 #ee ,kainosite1 #ah1 #de ,karyocerite1 #ab ,kataplejite1 #ab1 #ea ,keilhauite1 #ah1 #eb ,kischtimite1 #ah1 #ha ,knopite1 #ah1 #ei ,kochelite1 #ah1 #fd ,koppite1 #ah1 #fd ,lanthanite1 #ah1 #gi ,lanthanum1 atomic weight of1 #agc compounds of1 #agb detection of1 #agc metallic1 #aae1 #aga separation of1 #agj ,lavenite1 #ai1 #ea ,lead1 #aje1 #ajg ,lederite1 #ed ,leucosphenite1 #ai1 #ee ,leucoxene1 #ee ,lewisite1 #ai1 #ei ,lighting devices1 #cae ,ligurite1 #ed ,loranskite1 #ai1 #fd ,lorenzenite1 #ai1 #ee ,lutecium1 #bje ,mackintoshite1 #ai1 #gi ,magnetic susceptibility1 #aeb ,malacone1 #ai1 #di ,mauzeliite1 #bj1 #ei ,melanocerite1 #bj1 #ea ,menaccannite1 #eg ,mengite1 #hd ,mesothorium1 #beb1 #bgf ,metals of rare earth group1 #aad ,michaelsonite1 #ad ,microlite1 #bj1 #fd ,misch metal1 #aae1 #cae ,molengraafite1 #bj1 #ee ,monazite1 #d1 #bj1 #hb sands1 #hc1 #ij technical treatment of1 #bgf ,mosandrite1 #bj1 #ee ,muromontite1 #bj1 #db1 #de ,naegite1 #ca1 #de1 #di ,narsarsukite1 #ba1 #ee ,neodymium1 atomic weight of1 #agi detection of1 #ahj metallic1 #aae1 #agg oxides1 #agg salts1 #agh ,neoytterbium1 #bjf ,neptunite1 #ba1 #ee ,nernst lamp1 #cbj ,nitrates of rare earth group1 #abh ,nitrides of rare earth group1 #aaf ,nivenite1 #ba1 #gc ,nohlite1 #ba1 #fd ,octahedrite1 #h1 #gh ,oerstedite1 #ba1 #di ,oisanite1 #gh ,orangite1 #ba1 #de ,organic salts of rare earth group1 #acc ,orthite1 #h1 #ci ,oxalates of rare earth group1 #aca ,oxides of rare earth group1 #aae1 #aag ,parisite1 #ba1 #hj ,pauly process1 #cjc ,perovskite1 #ad1 #bb1 #ei ,peroxides of rare earth group1 #aag ,pertitanates1 #bce ,phosphates of rare earth group1 #abi ,phthalates of rare earth group1 #acd ,picroilmenite1 #af1 #ei ,pictite1 #ed ,pilbarite1 #bb1 #di ,pitchblende1 #bb1 #gb ,platinocyanides of rare earth group1 #abc ,platinum mantles1 #bfh ,plumboniobite1 #bb1 #fb ,polonium1 #ii ,polycrase1 #bb1 #ff ,praseodymium-- atomic weight of1 #age compounds of1 #agd detection of1 #agf history of1 #afh metallic1 #aae1 #agd separation of1 #agj ,priorite1 #bb1 #ff ,pseudobrookite1 #bb1 #ei ,pyrochlore1 #bc1 #ga ,pyromorphite1 #aja ,pyrophanite1 #bc1 #ei ,pyrophoric alloys1 #cad ,radioactivity1 #ii ,radiothorium1 #gd1 #ii1 #bec ,ramie1 mantles of1 #bia ,rare earth mixtures1 examination of1 #adg ,rare earths-- extraction of1 from minerals1 #adg and periodic classification1 #ace ,retzian1 #bc1 #hh ,rhabdophane1 #bc1 #hh ,rhnite1 #bc1 #ee ,rinkite1 #bc1 #ee ,risrite1 #bc1 #ch1 #fi1 #ajb ,rogersite1 #bd1 #fd ,rosenbuschite1 #bd1 #ee ,rowlandite1 #bd1 #ee ,rutile1 #bd1 #de1 #gg1 #ij ,samarium1 atomic weight of1 #ahb detection of1 #ahc history of1 #afh metallic1 #aae1 #aha salts of1 #ahb separation of1 #aga ,samarskite1 #bd1 #ch1 #fj1 #ia ,scandium1 atomic weight of1 #bag 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of1 #bed detection of1 #bfc estimation of1 #bhe extraction of1 #bea1 #bge1 #bhc group relations of1 #bbj metallic1 #bec radiochemistry of1 #beb separation of1 #bgg sulphate purification of1 #bgi ,thorogummite1 #bf1 #di ,thortveitite1 #bf1 #dd ,thulium1 history of1 #aid1 #bjc individuality of1 #bjd salts of1 #bjd separation of1 #aif ,titanates1 #bcd ,titaniferous ironstone1 #eg ,titanite1 #bf1 #eb1 #ij ,titanium1 atomic weight of1 #bcf compounds for fixation of nitrogen1 #ccg compounds of1 in dyeing1 #ccc compounds of divalent1 #bbe compounds of trivalent1 #bbf compounds of tetravalent1 #bcj cyanonitride1 #bbd detection of1 #bcf electrodes1 #cca estimation of1 #cch group relations of1 #bai metallic1 #bbc occurrence and extraction of1 #bbb olivine1 #bf1 #ee steels1 #cbi uses of1 in metallurgy1 #cbg1 #ccj ,tritomite1 #bf1 #ea ,tscheffkinite1 #bf1 #ee ,tungsten1 #a1 #ca ,turnerite1 #hc ,tyrite1 #fc ,tysonite1 #bf1 #hi ,uhligite1 #bg1 #ei ,uraninite1 #bi1 #eb ,uranosphrite1 #gc ,urano-tantalite1 #fj ,vasite1 #db ,vietenghfiote1 #bg1 #fd ,viscose process1 #cjd ,warwickite1 #bg1 #ei ,weibyite1 #bg1 #ha ,wiikite1 #bg1 #gj ,whlerite1 #bh1 #gj ,wolframite1 #b1 #bad ,xenotime1 #bh1 #de1 #hf1 #ij1 #bjg ,ytterbia1 #a1 #bjf ,ytterbite1 #a1 #cc ,ytterbium1 atomic weight of1 #bjf detection of1 #bjg history of1 #aid1 #bje salts of1 #bjf separation of1 #aif1 #bje ,yttria1 #a1 #ce1 #aaa1 #bji ,yttrialite1 #bh1 #cd1 #de ,yttrium1 atomic weight of1 #baa detection of1 #bab group1 history of1 #aid separation of1 #aie history of1 #aid1 #bjh salts of1 #baj separation of1 #aif1 #bje ,yttrocerite1 #bh1 #hh ,ythrocrasite1 #bh1 #ef ,ythrofluirite1 #bh1 #hi ,yttrofluorite1 #bh1 #hi ,yttrogarnet1 #bh1 #de ,yttrogummite1 #bh1 #di ,yttroilmenite1 #fj ,yttrotantalite1 #bi1 #fb ,yttrotitanite1 #ah1 #eb ,zircon1 #bi1 #ch1 #de1 #dg1 #ij1 #ajg ,zirconia1 uses of1 #cbc ,zirconium1 atomic weight of1 #bdi compounds of1 #bdi detection of1 #bdb estimation of1 #bej extraction of1 #bci group1 relations of1 #bai1 #bdj history of1 #bch industrial applications of1 #cba ,zirkelite1 #bi1 #gi ,,printed ,,by ,,spottiswoode ,,and ,,co4 ,,ltd41 ,,colchester ,,london ,,and ,,eton ,transcriber's ,notes ,inconsistent and unusual spelling and hyphenation 7including those of proper and geographical names7 have been retained1 except as mentioned below4 ,depending on the hard- and software used and their settings1 not all elements may display as intended4 ,lists of elements were printed both with and without separating commas 7for example1 ,r ,ca1 ,fe1 ,be and ,r ,,nh1,k1,rb1,cs72 these have not been standardised4 ,pages #cd1 weighing #bjj lb43 later 7page #da7 referred to as weighing #cjj lb4 ,some tables appear to use nm1 others 2 this has not been standardised4 ,page #aha1 table3 #eibcce may be an error2 it is out of sequence4 ,page #bjj1 table3 #cgie may be an error2 it is out of sequence4 ,page #bcf1 7,,nh7,o1,ti,o1,h,o3 as printed in the source document2 the final ,o is probably an error4 ,changes3 ,footnotes have been moved to under the paragraph in which they are referenced2 illustrations have been moved out of text paragraphs4 ,some obvious minor typographical and punctuation errors have been corrected silently4 ,moh's scale has been changed to ,mohs' scale1 ,gurin and ,gurin to ,gurin4 ,where there was a space between the number and the percent sign1 or between the degree sign and the ,c1 this has been deleted for the sake of consistency4 ,page vii3 ,blomstandine changed to ,blomstrandine4 ,page #bj1 ,monazite3 ,yttr #a #d2 changed to ,yttr #a-d2 ,page #bf3 ,osterby changed to sterby4 ,page #df3 ,struverite changed to ,strverite as elsewhere4 ,page #hg3 ,kraus and ,heitinger changed to ,kraus and ,reitinger4 ,page #aee3 ,footnote anchor #aid was missing in the source document1 and has been inserted at the end of the paragraph4