,transcriber's ,notes3 ,underscores 80 before and after a word or phrase indicate italics in the original text4 ,small capitals have been converted to ,,solid capitals4 ,typographical and punctuation errors have been silently corrected4 ,the symbol 80 7small i with macron7was used in place of the numeral #a 7one7 with macron4 ,the symbol 8#b0 7overline #b7 was used in place of numeral #b with macron4 ,determination of ,the ,atomic ,weight of ,cadmium and ,the ,preparation of ,certain ,of ,its ,sub-,compounds4 ,dissertation1 ,presented to ,the ,board of ,university ,studies of ,the ,johns ,hopkins ,university1 ,for ,the ,degree of ,doctor of ,philosophy1 ,by ,harry ,c4 ,jones #ahib4 ,contents4 ,page ,determination of the ,atomic ,weight of ,cadmium #a ,introduction and ,historical ,statement #b ,preparation of ,pure ,cadmium #bb ,the ,preparation of ,pure ,nitric ,acid #bh ,the ,arrangement of ,crucibles #cj ,the ,mode of ,procedure #cb ,the ,weighing #cg ,taring the ,crucibles #dj ,the ,results #db ,objections to the ,method #de ,advantages of the ,method #dh ,the ,oxalate ,method #ej ,preparation of ,pure ,oxalic ,acid #ea ,preparation of ,cadmium ,oxalate #eb ,mode of ,procedure #ec ,the ,drying and ,weighing of the ,oxalate #ee ,the ,results #eh ,advantages of the ,method #fj ,disadvantages of the ,method #fa ,preparation of ,certain ,sub-compounds of ,cadmium #fc ,historical #fd ,the ,preparation of ,cd,cl #ff ,the ,preparation of ,cd,br #gh ,the ,preparation of ,cd,i #hb ,the ,preparation of ,cadmium ,hydroxide and ,oxide #hb ,notes on ,crystals of ,metallic ,cadmium #ig ,the ,cohesion ,phenomena of ,cadmium #ajc ,biographical ,sketch #ajf ,acknowledgment4 ,it affords me great pleasure to express my sincere thanks to ,professor ,remsen for his instruction and personal supervision during my entire connection with the ,university2 to ,dr4 ,morse1 under whose immediate guidance the work described in this dissertation was completed2 to ,dr4 ,renouf for valuable assistance in qualitative chemistry and to ,dr4 ,williams1 with whom the branches of mineralogy and geology were followed as subordinate subjects4 ,determination of the ,atomic ,weight of ,cadmium4 ,introduction and ,historical statement4 ,a careful examination of the literature on the atomic weight of cadmium will convince any one that considerable uncertainty yet remains in reference to this constant4 ,six experimenters have worked on this problem but the results of no one of them can be accepted as being more accurate than those of all others4 ,the value assigned to cadmium varies from #aaa4dh to #aab4cb on the basis of oxygen #af4 ,the best work has apparently been done by von ,hauer1 ,lenssen and ,huntington4 ,the results of these three seem entitled to about equal confidence1 yet the figure obtained by von ,hauer differs from that of ,huntington by three tenths of a unit4 ,the more prominent difficulties which have been encountered were3 ,first4 ,the preparation of cadmium compounds free from all impurities1 and which at the same time were well adapted to weighing4 ,second4 ,the lack of a thoroughly simple and exact method for the analysis of cadmium compounds4 ,third4 ,insufficient care in weighing in many cases whereby small errors were introduced into the results4 ,the methods which have been employed are3 #a ,conversion of the metal into the oxide4 7,stromeyer74 #b ,conversion of the sulphate into the sulphide4 7von ,hauer and ,partridge74 #c ,decomposition of the oxalate to the oxide4 7,lenssen and ,partridge74 #d ,determination of the chlorine in cadmium chloride1 by which the relation between the chloride and metallic silver was established4 7,dumas47 #e ,precipitation of the bromine in cadmium bromide as silver bromide4 7,huntington47 #f ,the conversion of the oxalate into the sulphide4 7,partridge47 ,the different pieces of work will be taken up in chronological order and briefly considered4 ,stromeyer1 ,schurigg ,journ4 #bb1 #cff4 #ahah1 determined the atomic weight of cadmium a short time after the discovery of the element4 ,he does not describe his method in detail but established the relation between cadmium and oxygen to be3 ,cd 3 ,o #ajj 3 #ad4ceb4 ,if the atomic weight of oxygen #af1 0 0 0 0 cadmium #aaa4dhc4 ,the very low result as compared with all subsequent work was probably due to the presence of a small amount of zinc1 since the cadmium used was obtained from zinc ores and no adequate means of separation from the zinc is described4 von ,hauer1 ,journ4 f4 prakt4 ,chem4 #gb1 #cch4 #aheg4 ,his method consisted in reducing a weighed amount of cadmium sulphate to the sulphide in a stream of hydrogen sulphide1 under pressure1 at an elevated temperature1 and weighing the sulphide4 ,the reduction was shown to be complete by proving the absence of sulphate in the sulphide4 #fd4bjea grams of cadmium sulphate gave #dd4ddia 0 0 0 sulphide4 ,if the atomic weight of oxygen #af1 0 0 0 0 0 sulphur #cb4jei1 0 0 0 0 cadmium #aaa4ice4 ,the atomic weight of cadmium calculated as an average of the nine determinations made using the above values for oxygen and sulphur #aaa4id4 ,maximum1 #aab4aba4 ,minimum1 #aaa4gif4 ,mean1 #aaa4idj4 ,the work of von ,hauer is greatly to be preferred to that of ,stromeyer4 ,the large amount of material used in each determination tended to lessen any experimental error4 ,a very considerable degree of care seems to have been exercised in purifying the cadmium sulphate4 ,in determinations #a-e a different specimen of sulphate was employed from that in determinations #f-i4 ,the average value found in the first five determinations #aaa4iaj1 in the last four #aaa4igg4 ,the close agreement between the results obtained from the different preparations of the sulphate argues in favor of a fair degree of purity for all the material4 ,the method of weighing the more or less hygroscopic cadmium sulphate is open to criticism when employed in accurate work4 ,the cadmium sulphate was placed in an open boat1 dried1 cooled over sulphuric acid1 and weighed4 ,it was again dried1 cooled as before1 and weighed4 ,the second weighing could be quickly accomplished since the approximate weight was known4 ,the two weighings agreed to within less than a milligram or a third drying and weighing were made4 ,an error of a milligram in the weight of the sulphate produced an average error in the atomic weight of cadmium of about 4#jf4 ,that a discrepancy of greater or less magnitude was introduced from this source will be readily seen4 ,dumas ,ann4 ,chim4 ,phys4 #ee1 #aeh4 #ahei1 determined the relation between cadmium chloride and the metallic silver required to precipitate the chlorine4 ,metallic cadmium was dissolved in boiling hydrochloric acid and the solution evaporated4 ,the cadmium chloride was fused for five or six hours in a stream of hydrochloric acid gas4 ,six determinations were made4 #bc4jfde grams of cadmium chloride were equivalent to #bg4agc grams of metallic silver4 ,if the atomic weight of silver #ajg4ic4 0 0 0 0 0 chlorine #ce4de4 0 0 0 0 cadmium #aab4cbb4 ,the atomic weight of cadmium calculated as the average of the six determinations made1 using the above values for silver and chlorine #aab4bda4 ,maximum1 #aab4gei4 ,minimum1 #aaa4gef4 ,mean1 #aab4bda4 ,the large difference between the results would indicate some considerable source of error in part or all of the determinations4 ,the first three determinations were made from a different specimen of cadmium from the last three4 ,in the first three the cadmium used does not seem to have been purified and the cadmium chloride prepared from it was more or less tinted brown4 ,in the last three a new specimen of metal was used which in ,dumas' words could reasonably be considered to be absolutely pure4 ,the chloride prepared from it was colorless1 well crystallized and perfectly soluble in water4 ,in order to show clearly the wide discrepancy between the results obtained from the two specimens of cadmium which were used1 the separate determinations are given in detail4 ,at4 ,wt4 ,cd,cl ,ag4 ,cadmium4 #a #b4cfi #b4gia #aab4cbb #b #d4edj #e4cdh #aab4cdg #c #f4agg #g4bfj #aab4gei #d #b4djd #b4hda #aaa4gef #e #c4ecbe #d4aff #aab4ace #f #d4jdb #d4gfg #aab4acj ,the average result of the first three determinations #aab4dgf4 ,the average result of the last three determinations #aab4jjg4 ,from ,dumas' own statement concerning the purity of the cadmium chloride analyzed1 determinations #d-f are much to be preferred to determinations #a-c and the most probable value from ,dumas' work would be very nearly #aab4 ,lenssen ,journ4 f4 prakt4 ,chem4 #gi1 #bha4 #ahfj1 regarded the oxalate of cadmium as well adapted to the determination of the atomic weight of cadmium4 ,a solution of cadmium chloride which had been purified by repeated crystallization was treated with an excess of a solution of pure oxalic acid4 ,the cadmium oxalate formed was filtered off1 washed1 and carefully dried in the air at #aej ,c4 until the last trace of water was removed4 #a4efig grams cadmium oxalate gave #a4jjdg grams cadmium oxide4 ,if the atomic weight of oxygen #af1 0 0 0 0 carbon #ab4jjc1 0 0 0 cadmium #aab4jdc4 ,the average of the three determinations using the above values for oxygen and carbon is #aab4jfg4 ,maximum1 #aab4cjd4 ,minimum1 #aaa4iaa4 ,mean1 #aab4jfg4 ,the small amount of material used in each determination1 the small number of determinations made1 and the rather large difference between the highest and lowest result are objectionable4 ,there are certain weak points in the method but to these reference will be made later4 ,huntington1 ,proc4 ,amer4 ,acad4 #ag1 #bh4 #ahhb1 working with ,cooke1 made two series of determinations of the atomic weight of cadmium4 ,in the first series the relation between cadmium bromide and the silver bromide formed from it was determined4 ,in the second1 the relation between cadmium bromide and the silver required to precipitate the bromine4 ,the cadmium bromide was prepared by dissolving the carbonate in hydrobromic acid and subliming the product in a stream of carbon dioxide4 ,in the first series of eight determinations #bc4cbge grams of cadmium bromide were equivalent to #cb4bjih grams of silver bromide4 ,if the atomic weight of silver #ajg4ic4 0 0 0 0 0 bromine #gi4ie4 0 0 0 0 cadmium #abb4bci4 ,maximum1 #aab4bij4 ,minimum1 #aab4afi4 ,where the difference between the maximum and minimum value is slight1 the average of the separate determinations agrees closely with the number found by comparing the total substance used with the total product obtained4 ,the latter method of calculation seems however to be preferable4 ,in the second series of eight determinations #bh4fffh grams of cadmium bromide were equivalent to #bb4gcgi grams of silver4 ,using the same values for silver and bromine1 the atomic weight of cadmium #aab4bde4 ,maximum1 #aab4cbj4 ,minimum1 #aab4ahj4 ,the agreement of the separate determinations with each other is fairly close and the average of the two series of determinations is nearly the same4 ,huntington took great care in the purification of his material and in the carrying out of his method1 which are strong arguments in favor of his work1 yet his method is not as simple as could be desired where the nature of the work demands the greatest possible accuracy in all details and it also appears to be subject to some of the errors common to ordinary analytical operations4 ,partridge4 ,amer4 ,journ4 ,science ,,xl1 #cgg4 #ahij4 ,methods3 #a4 ,decomposition of the oxalate to the oxide4 #b4 ,reduction of the sulphate to the sulphide4 #c4 ,conversion of the oxalate into the sulphide4 ,as an average of the determinations made by each method ,partridge gives3 #a series1 atomic weight of cadmium #aaa4hjbg4 #b 0 0 0 0 0 #aaa4gifi4 #c 0 0 0 0 0 #aaa4hjej4 ,an excellent agreement between results obtained by different methods#a4 ,that this very close agreement is only apparent has been shown by ,clarke4 ,he has found that the above calculations are based on the assumption that the atomic weight of carbon #ab1 and that of sulphur #cb when oxygen #af4 ,there seems to be little justification for this rather arbitrary selection by ,partridge since the most refined work shows that whole numbers do not express the most probable atomic weights of carbon and sulphur in a system where oxygen #af4 #a ,amer4 ,chem4 ,journ4 #ac1 #cd4 #ahia4 ,the atomic weight of cadmium calculated from the total material used and the total product found in each of the three series is3 ,o #af4 ,c #ab4 ,s #cb4 ,at4,wt4,cd4 #a series1 ,cd,c,o 3 ,cd,o #ab4ffcfh;g4 3 #h4ajjca;g4 #aaa4hje4 #b 0 ,cd,s,o 3 ,cd,s #ae4iceje;g4 3 #aa4jbfia;g4 #aaa4ghf4 #c 0 ,cd,c,o 3 ,cd,s #af4hebbh;g4 3 #ab4abijf;g4 #aaa4hjf4 difference1 #j4jbj4 ,o #af4 ,c #ab4jjc ,s #cb4jei ,at4,wt4,cd4 #a series1 ,cd,c,o 3 ,cd,o #ab4ffcfh;g4 3 #h4ajjca;g4 #aaa4haf4 #b 0 ,cd,s,o 3 ,cd,s #ae4iceje;g4 3 #aa4jbfia;g4 #aaa4gbg4 #c 0 ,cd,c,o 3 ,cd,s #af4hebbh;g4 3 #ab4abijf;g4 #aaa4faj4 difference1 #j4bjf4 ,as ,clarke has pointed out when those values are chosen for carbon and sulphur which are founded on the best experimental evidence the agreement between the different series of results as calculated by ,partridge is somewhat modified4 ,i have repeated the work on which series ,i is based and would call attention to the following points in which it appears to have been experimentally defective4 #a ,the metal was only distilled twice in a vacuum4 ,it has been found in this laboratory that perfectly pure cadmium or zinc can be prepared only by repeated distillations1 each one being carried on slowly to allow the impurities to separate by means of their difference in volatility4 #b ,the supposed mixture of metal and oxide resulting from the decomposition of the oxalate was only moistened with a few drops of nitric acid in order to reoxidize any reduced metal4 ,unless the entire mass of metal and oxide was dissolved there would be danger of the presence of free undissolved metal which would possess an appreciable vapor-tension below the temperature of decomposition of cadmium nitrate4 ,an appreciable loss in weight resulting from a distillation of the metal out of the crucible might easily result4 #c ,it seems very probable that the cadmium nitrate was not heated sufficiently to remove all traces of the oxides of nitrogen4 ,i have found that this could only be accomplished by long continued heating4 ,constant weight was not sufficient to have decided this point since it was also found that this could be reached short of complete decomposition1 if the temperature was too low to remove the last traces of these oxides4 ,some very delicate test for such oxides should have been applied at the end of each experiment4 ,the following table contains a summary of the results thus far obtained4 ,when two values are given for one series of determinations1 the first is calculated from the total material used and the total product found1 the second is an average of the results of the separate experiments4 ,oxygen is taken as #af throughout4 ,date4 ,investigators4 ,at4,wt4,cd4 #ahah1 ,stromeyer1 #aaa4dhc #aheg1 von ,hauer1 #aaa4ice #aaa4idj #ahei1 ,dumas1 #aab4cbb #aab4bda #ahfj1 ,lenssen1 #aab4jdc #aab4jfg #ahhb1 ,huntington1 #a series #aab4bci 0 #b 0 #aab4bde #ahij1 ,partridge1 #a series #aaa4hje 0 #b 0 #aaa4ghf 0 #c 0 #aaa4hjf ,in the above calculation of ,partridge's results ,c #ab4 ,s #cb4 ,in the following carbon is taken as #ab4jjc and sulphur is #cb4jei4 #ahij1 ,partridge1 #a series #aaa4haf 0 #b 0 #aaa4gbg 0 #c 0 #aaa4faj ,after a careful examination of the methods available it becomes evident that no one of them was per se as accurate as the method employed by ,morse and ,burton1#b for the determination of the atomic weight of zinc1 and more recently by ,burton and ,morse1#c for the determination of the atomic weight of magnesium4 ,the method of work was to prepare pure metallic cadmium1 to convert a weighed portion of the metal into nitrate by means of pure nitric acid1 to decompose the nitrate completely to oxide and to weigh the oxide4 #b ,amer4 ,chem4 ,journ4 ,x1 #caa4 #c ib4 ,,xii1 #bai4 ,preparation of ,pure ,cadmium4 ,the work of preparing pure cadmium was begun more than two years ago by ,mr4 ,w4 ,v4 ,metcalf with ,dr4 ,h4 ,n4 ,morse4 ,i wish to express here my sincere thanks to him for the material with which the following determinations were made4 ,the cadmium used by him was obtained from ,schuchart and marked 8,met4 prss4 7galv47 redus40 ,the method of purification by fractional distillation in a vacuum1 was essentially that employed by ,morse and ,burton for the purification of metallic zinc4 ,the distillation was carried out in hard glass tubes of the size of ordinary combustion tubing4 ,illustration3 ,,fig4 #a4 ,fig4 #a4 represents such a tube4 ,a hard glass tube1 #fjj-gjj mm4 in length1 was closed at one end and about #acj grams of cadmium introduced4 ,the walls of the tube were heated and indented at the two points a1 and b1 with a red-hot file1 dividing the tube into three sections marked ,a1 ,b and ,c4 ,the open end of the tube was drawn out1 bent1 and attached to a ,sprengel air-pump by means of a rubber tube4 ,the joint was tied tightly with waxed cord and surrounded by mercury4 ,when the manometer indicated that the tube was exhausted1 it was gradually heated by the combustion furnace in which it rested4 ,the metal in ,a melted and distilled slowly into the front portion of the tube4 ,most of it condensed in ,b1 while a small part1 together with any more volatile impurity1 collected in ,c which was kept cooler than the remainder of the tube4 ,when about four-fifths of the metal placed in ,a had distilled over1 the tube was very slowly cooled4 ,when cold1 the tube was broken open1 the portions in ,a and ,c being rejected in every case1 while the metal was recovered from ,b in the form of a bar resting on the bottom of the tube1 together with some crystal aggregates1 suspended from the top and sides4 ,a few crystal individuals were secured but the measurement of these will be considered later4 ,the metal separated from the glass with a highly lustrous surface and did not attack the glass in the least4 ,the first distillation was effected in a tube bridged as represented in ,fig4 #a1 but drawn out at each end4 ,the original cadmium powder was heated in the tube in a stream of pure hydrogen gas1 for the purpose of obtaining the metal in the form of bars1 and to reduce any cadmium oxide contained in the powder4 ,six distillations were made in a vacuum4 ,in the first1 #fcj grams of metal were used being distilled in quantities of about #acj grams each4 ,at the end of the sixth distillation1 there were about #ajj grams of pure cadmium at disposal4 ,in the fifth and sixth distillations1 the metal was heated just above the melting point for from twenty to twenty-four hours1 before being forced over into the middle portion of the tube4 ,by this means all the remaining traces of the more volatile arsenic were driven into the front part of the tube and separated from the cadmium4 ,the distillations4 ,the residue represents the undistilled portion remaining in ,a4 ,the distillate1 the material obtained from ,b after the distillation was completed4 ,the coating1 the substance which condensed in ,c4 ,residue1 ,cd1 ,pt1 ,zn18 ,as84 ,distillation ,i ,distillate1 ,cd1 ,zn18 ,as8 ,coating1 ,cd1 ,zn18 ,as84 ,residue1 ,cd1 ,zn81 ,as84 ,distillation ,,ii ,distillate1 ,cd1 ,zn81 ,as84 ,coating1 ,cd1 ,zn81 ,as84 ,residue1 ,cd1 ,zn81 ,as84 ,distillation ,,iii ,distillate1 ,cd1 ,zn81 ,as84 ,coating1 ,cd1 ,zn81 ,as84 ,residue1 ,cd1 ,zn81 ,as84 ,distillation ,,iv ,distillate1 ,cd1 ,zn81 ,as84 ,coating1 ,cd1 ,zn81 ,as84 ,residue1 ,cd4 ,distillation ,v ,distillate1 ,cd4 ,coating1 ,cd1 ,as84 ,residue1 ,cd4 ,distillation ,,vi ,distillate1 ,cd4 ,coating1 ,cd4 ,the distillate from the last distillation was examined spectroscopically by ,professor ,rowland and found to be free from all traces of impurity which would be detected by that method4 ,the chemical test for arsenic was more delicate than the spectroscopic and this failed to reveal a trace4 ,the preparation of pure nitric acid4 ,the method of preparing the pure acid and of preserving and transferring it was the same as adopted by ,morse and ,burton in their work on the atomic weight of zinc4 ,illustration3 ,,fig4 #b4 ,the simple form of apparatus is represented in fig4 #b4 ,a large platinum vessel containing fragments of ice was supported on a smaller platinum dish1 from which it was separated by hooks of large platinum wire4 ,the acid was distilled from a small flask as represented in the drawing4 ,the purest nitric acid which could be obtained was diluted with about an equal volume of water4 ,the vessel containing the acid was heated very gently that the distillation might take place without boiling4 ,the dilute acid condensed on the cold surface of the larger dish and collected in the smaller1 in which it was preserved until used4 ,this acid gave no residue on evaporation4 ,the arrangement of crucibles4 ,illustration3 ,,fig4 #c4 ,the arrangement of the crucibles in which the determinations were made is represented in fig4 #c4 #a is a small porcelain crucible1 7#jj7 from the exterior and lid of which the glaze had been removed by hydrofluoric acid4 ,the lid was separated from the crucible by hooks made from thick platinum wire1 to allow free communication between the contents of the crucible and the external air4 ,this would facilitate the outward diffusion of the oxides of nitrogen when liberated from the nitrate4 #b is an uncovered porcelain crucible 7no4 ,,ii7 in which #a was placed4 ,from the exterior the glaze had been removed to prevent the crucible from adhering to the unglazed porcelain scorifier on which it rested4 ,the exterior was carefully brushed after treatment with hydrofluoric acid to remove all loose particles adhering to its surface4 ,crucibles #a and #b were not separated during a determination4 #c is a nickel crucible about two and a half inches in diameter4 ,the porcelain crucibles were not allowed to touch the nickel at any point4 ,the nickel crucible was covered by a lid of nickel4 ,the mode of procedure4 ,a piece of cadmium weighing from two to three grams was cut from the bar of the metal by means of a steel chisel4 ,this was seized with steel forceps and filed with a hard steel file to about one half the original weight4 ,care was taken to remove the entire exterior portion of the metal which had come in contact with the chisel or had stood exposed to the air4 ,the plug of metal was then carefully brushed and examined with a lens to insure the removal of all loose particles from the surface4 ,crucibles #a and #b having been brought to constant weight against their tare1 were ready for use4 ,the piece of cadmium was weighed and placed in #a4 ,an excess of pure nitric acid was added and a gentle heat applied until all the metal had dissolved4 ,this required from twenty to forty hours4 ,a sand-bath was constructed by placing a large porcelain crucible in an iron crucible and filling the intervening space with sand4 ,the pair of crucibles 7#a and #b7 was placed in the porcelain crucible and the contents evaporated to dryness by warming very carefully at first and gradually increasing the temperature4 ,the pair of crucibles was then transferred to a bath constructed as the above where iron filings took the place of sand4 ,this was heated by a single burner until the nitrate was all decomposed when a triple burner was added and finally two for six or eight hours4 ,this was not sufficient to effect complete decomposition4 ,when cold1 the pair of crucibles was placed in the nickel crucible as represented in fig4 #c and sharply heated over a blast-lamp for several hours4 ,this completed the decomposition of the nitrate and the removal of the last traces of oxides of nitrogen4 ,during the blasting the lid on crucible #c was raised a little to one side to allow free access of air4 ,the nickel crucible was forced tightly into a hole cut in the center of an asbestos board about ten inches in diameter1 to prevent any reducing gases from the lamp entering the crucibles while hot4 ,this was the same arrangement as was used by ,partridge#d4 #d ,amer4 ,journ4 ,science ,,xl1 #cgi4 ,it was found that the final decomposition of the nitrate could not be effected in a muffle furnace as with zinc1 since at very high temperatures cadmium oxide attacked the porcelain with great energy and injured the crucibles4 ,the decomposition of the nitrate was shown to be complete not by constant weight alone1 but by testing for oxides of nitrogen with starch paste rendered extremely sensitive with potassium iodide4 ,that the test should be reliable1 ,morse and ,burton have pointed out that all the reagents used must be free from oxidizing agents4 ,the presence of iodate in the iodide is especially to be avoided4 ,this was removed by boiling the solution with zinc amalgam4 ,air was removed from all the solutions by boiling4 ,when the starch-potassium-iodide solution had been prepared as sensitive as possible1 a portion of it was treated with a little hydrochloric acid1 to determine if any iodine was liberated4 ,if no coloration was observed the cadmium oxide was added4 ,it dissolved in the hydrochloric acid and if any oxides of nitrogen were present they would have revealed themselves by the liberation of iodine and a blue coloration of the starch paste4 ,in no one of the ten determinations was the slightest coloration detected4 ,an equal volume of nitric acid was added to the pair of crucibles used as a tare as to those containing the determination1 and they were heated in exactly the same manner and for the same length of time4 ,the crucibles containing the cadmium oxide were heated over the blast-lamp for an hour1 weighed against their tare1 reheated1 again weighed1 and this continued until there was no further change in weight4 ,usually from two to four hours heating over the blast-lamp was sufficient to completely decompose the nitrate4 ,the test for oxides of nitrogen was then applied4 ,i found that practically constant weight could be reached short of compete decomposition1 at a temperature below that necessary to transform all the nitrate into the oxide4 ,this necessitated the final test for oxides of nitrogen4 ,the ,weighing4 ,the balance used was a ,no4 #h long-armed one1 made by ,becker and ,sons4 ,it was supported by iron brackets fastened to one of the foundation walls of the laboratory4 ,here it would be subjected to the least jar and was also well protected from air currents4 ,all weighings were made between the hours of one and five in the morning when the surroundings were as quiet as could be desired4 ,a very slight disturbance was detected by the vibrations on the surface of a cup of mercury placed conveniently between the pans4 ,that the presence of the operator might not produce any change in the balance during the weighing1 he closed the room1 placed the light above and behind his head and took his position in front of the balance at least an hour before making a weighing4 ,when his presence no longer affected the balance 7which was shown by the zero point remaining constant in a series of determinations7 the weighing was begun4 ,the method of weighing by vibrations and upon both pans was employed throughout4 ,each zero point was taken as the mean of three closely agreeing zero determinations2 each one of the three being the mean of seven readings4 ,the zero of the balance empty was determined just before and after each weighing to detect any change in its position4 ,usually none was observed4 ,the sensibility of the balance was taken at each weighing with the weights used at that weighing4 ,a displacement of the zero point about six divisions of the ivory scale was effected by the addition of one milligram4 ,the weights had been especially adjusted and were carefully compared with each other before using4 ,weighing by tares was adopted as preferable to any other method4 ,by this means all errors resulting from changes in the moisture of the air were avoided and any errors which might have been introduced by heating or manipulating the crucibles would be counteracted by treating the tare in exactly the same manner4 ,taring ,the ,crucibles4 ,a pair of crucibles 7#a and #b in the figure7 was selected and treated as described4 ,another pair about the same size but a little lighter was prepared in exactly the same way4 ,each pair was placed in the nickel crucible and heated by means of the blast-lamp for half an hour4 ,after cooling in desiccators1 both pairs of crucibles where placed in the closed balance until no longer affected by the moisture of the air1 which was also dried by calcium chloride4 ,the tare was brought to within one tenth of a milligram of the weight of the crucibles against which it was being tared1 by adding fragments of porcelain obtained from another crucible of the same composition4 ,the difference in weight between the tare and its mate was then accurately ascertained4 ,each pair of crucibles was again placed in the nickel crucible and blasted for half an hour4 ,they were then reweighed1 to determine if the difference in weight previously found had remained constant4 ,in no case was any change detected1 yet this precaution was always taken4 ,the ,results4 ,the following table contains the results of ten successive determinations4 ,at4 ,wt4 ,cd4 ,at4 ,wt4 ,cd4 ,wt4 of ,cd4 ,wt4 of ,cd,o4 7,o #af7 7,o #ae4if7 ,i #a4gghia #b4jcbhh #aab4jgj #aaa4gij ,,ii #a4hbdib #b4jhedd #aab4jgh #aaa4gih ,,iii #a4gdfhh #a4iifbf #aab4jgh #aaa4gih ,,iv #a4egjjj #a4gidah #aab4jec #aaa4ggc ,v #a4ihdha #b4bfhbj #aab4jfa #aaa4gha ,,vi #b4bgbig #b4eigea #aab4jei #aaa4ggi ,,vii #a4gefie #b4jjgge #aab4jhf #aaa4hjf ,,viii #a4gjjbh #a4idcje #aab4jei #aaa4ggi ,,ix #a4ibbcg #b4aifgi #aab4jhc #aaa4hjc ,x #a4ibjha #b4aiejb #aab4jgh #aaa4gih ------- ------- ------- ------- ,mean1 #aab4jgje4 #aaa4gije4 ,maximum1 #aab4jhf4 #aaa4hjf4 ,minimum1 #aab4jec4 #aaa4ggc4 ,difference1 4#jcc4 4#jcc4 ,calculating the atomic weight of cadmium from the total amount of metal used and oxide found1 we have3 ,at4 ,wt4 of ,cd4 ,at4 ,wt4 of ,cd4 7,o #af7 7,o #ae4if7 #aab4jgjf4 #aaa4gijd4 ,these results agree more closely with those of von ,hauer and ,lenssen than with those of any other experimenter4 ,the following table gives a comparison of the work of these investigators with that herein described3 von ,hauer4 ,lenssen4 ,work here described4 #i determinations4 #c determinations4 #aj determinations4 7,o #af7 7,o #af7 7,o #af7 ,mean #aaa4idj #aab4jfg #aab4jgje ,max4 #aab4aba #aab4cjd #aab4jhf ,min4 #aaa4gif #aaa4iaa #aab4jec ,diff4 4#cbe 4#cic 4#jcc ,a difference of three or four tenths of a unit between the different results of a series leaves considerable doubt as to the accuracy of the method employed and to the value obtained4 ,the figure selected by ,ostwald1#e as most probable for the atomic weight of cadmium is #aab4jh4 ,this is the mean of the results on von ,hauer and ,huntington4 ,my own work leads me to believe that this number is very close to the true value when oxygen is taken as #af4 #e ,lehrb4 d4 ,allg4 ,chem4 ,i1 #fj4 ,objections to the method4 ,marignac#f offered the objection to this method for determining the atomic weight of zinc that the zinc oxide dissociated when heated in platinum over the blast-lamp4 ,the same objection might be urged against this method for determining the atomic weight of cadmium1 had it not been shown that the objection does not hold for zinc#g4 ,what took place was a reduction of the zinc oxide by the highly heated hydrogen which passed through the hot platinum4 #f ,archives des ,sciences ,phys4 et ,nat4 7#c7 #aj1 #aic4 #g ,amer4 ,chem4 ,journ4 ,x1 #adh4 ,it was shown that zinc oxide can be heated in a platinum vessel in a muffle furnace1 to the melting point of steel1 without undergoing any dissociation1 or in any wise losing in weight4 ,this source of error was avoided by using porcelain vessels1 which were not brought into contact with the free flame4 ,the statement of ,marignac that the oxide of zinc derived from the nitrate retains oxides of nitrogen even when heated to the temperature at which it begins to undergo dissociation1 was shown by the same authors to be without foundation4 ,the basis of this objection is doubtless to be found in the imperfect method of testing for such oxides4 ,it might be urged as an objection to this method that the difference in weight between the metal and oxide is not very great1 therefore any error in weighing would be multiplied in the result4 ,at first sight this objection may appear valid1 but since the substances weighed were so well adapted to that purpose and the weighings could be made with such a high degree of accuracy no appreciable error could have resulted from this source4 ,a crucible with its contents was repeatedly weighed against its tare and weights to ascertain the difference between successive weighings under the conditions employed4 ,a number of weighings agreed to 4#jjjjb gr4 and in some instances to half this amount4 ,advantages of the ,method4 #a ,the great advantage of the method is its extreme simplicity4 ,from the beginning of an experiment until the end the contents of the crucible are not brought into contact with any foreign substance4 ,by this means small errors resulting from incomplete precipitation1 and filtration and all other errors incident to ordinary processes of analysis were avoided4 #b ,the nature of the metal and its oxide rendered them well adapted to weighing4 ,the specific gravity of the metal and oxide approached so closely to that of the weights1 that it was unnecessary to reduce the weighings to a vacuum standard4 #c ,the advantages derived from weighing by tares have been pointed out4 #d ,the closely agreeing results speak strongly in favor of the accuracy of the method4 ,the ,oxalate ,method4 ,the method consists in taking a weighed amount of cadmium oxalate1 decomposing it by heat1 when a mixture of oxide and metal are said to be formed1 dissolving this mixture in nitric acid1 converting the nitrate into oxide and weighing the oxide4 ,lenssen#h obtained results by this method which agree very closely with those recorded in the earlier part of this dissertation4 ,working with the same method1 ,partridge#i arrived at a value about one fourth of a unit lower than that of ,lenssen4 #h ,journ4 f4 prakt4 ,chem4 #gi1 #bha4 #i ,amer4 ,journ4 ,science ,,xl1 #cgg4 ,it appeared desirable that this method should be repeated with the greatest care to ascertain what result it would give under the most favorable conditions4 ,having a supply of pure cadmium it was necessary to prepare pure oxalic acid4 ,preparation of ,pure ,oxalic ,acid4 ,the commercial acid was crystallized three times from cold water to separate it from acid oxalates4 ,it was then boiled for two days with a #ae per cent solution of hydrochloric acid1 to remove any mineral matter present4 ,the acid which crystallized from the hydrochloric acid solution was recrystallized twice from hot1 redistilled alcohol and twice from pure ether4 ,it was finally boiled with water to decompose any ethyl oxalate and twice crystallized from pure water4 ,the acid was dried in the air at ordinary temperatures4 ,this acid left no residue on ignition4 ,preparation of ,cadmium ,oxalate4 ,a piece of cadmium was dissolved in pure nitric acid4 ,on carefully evaporating the solution cadmium nitrate was obtained4 ,twenty-five grams of the nitrate were dissolved in #gej c4c4 of redistilled water4 ,somewhat less than an equivalent of the oxalic acid was dissolved in an equal volume of water1 and slowly added to the solution of the nitrate with constant shaking4 ,a little less than an equivalent of oxalic acid was used to avoid any tendency to form acid oxalates4 ,cadmium oxalate was precipitated on standing a few minutes as a white crystalline compound1 well adapted to washing4 ,the oxalate was filtered off and washed until the wash water was free from all traces of nitric acid4 ,it was then washed ten times with water which had been twice redistilled and dried in an air-bath for twenty hours at #aej;,c4 ,the arrangement of the crucibles which were weighed was in all respects like that in the preceding method4 ,mode of ,procedure4 ,the crucibles were heated1 tared1 and weighed exactly as in the preceding method4 ,the oxalate was weighed in ground-stoppered weighing tubes from which it was transferred to the inner of the two porcelain crucibles4 ,the pair of crucibles1 7#a and #b fig4 #c7 was placed in a third porcelain crucible and the whole system introduced into an upright air-bath4 ,the outer crucible was supported on a porcelain triangle about an inch from the bottom of the bath and was not allowed to touch its walls at any point4 ,the top of the bath was covered with a sheet of iron over which was placed an asbestos board4 ,the exterior was also covered with a lining of asbestos4 ,a thermometer was introduced well into the bath4 ,the temperature was allowed to rise slowly until the oxalate began to show a brown color around the edge4 ,from this stage the temperature was kept as low as possible in order to effect the decomposition4 ,when the oxalate was decomposed the bath was allowed to cool and the contents of the crucible completely dissolved in nitric acid4 ,the nitrate was evaporated to dryness and decomposed as in the method first described4 ,the end of the decomposition was determined in the same manner and the oxide1 free from all impurities1 weighed4 ,the ,drying and ,weighing of the ,oxalate4 ,it was necessary to dry the oxalate before weighing from fifteen to twenty hours at #aej;,c4 in addition to the twenty hours drying of the whole preparation4 ,at this temperature the last traces of moisture were removed by prolonged heating4 ,the weighing of the oxalate was made in the weighing glasses in which it was dried4 ,two of these glasses had been previously tared against each other1 using the lighter as the tare and adding fragments of glass to it until the difference in weight was a small fraction of a milligram4 ,the oxalate having been dried to constant weight1 was weighed4 ,it was then poured as carefully and completely as possible from the weighing glass into the crucible and the glass again weighed against its tare4 ,the difference in the two weights gave the amount of oxalate4 ,the glass and its tare were dried and reweighed to determine if the few milligrams of oxalate adhering to the walls of the glass had absorbed any moisture during the transfer of the oxalate4 ,in one experiment a slight difference was detected when a second drying and weighing were made4 ,the weight of the cadmium oxalate as obtained from the balance was corrected for the difference in specific gravity between the cadmium oxalate and the weights4 ,the ,results4 ,at4 ,wt4 ,at4 ,wt4 ,at4 ,wt4 ,at4 ,wt4 ,cd4 ,cd4 ,cd4 ,cd4 7,o#af7 7,o#af7 7,o#ae4if7 7,o#ae4if7 7,c#ab4jja7 7,c#ab4jjc7 7,c#aa4iga7 7,c#aa4igc7 ,cd,c,o ,cd,o ,i #a4ecicg 4#ihebf #aab4jbf #aab4jcc #aaa4gdf #aaa4gec ,,ii #a4ggdhc #a4acehb #aaa4iha #aaa4ihh #aaa4gja #aaa4gjh ,,iii #a4gjbaa #a4jhidi #aab4jdi #aab4jef #aaa4gfi #aaa4ggf ,,iv #a4gjbch #a4jhifg #aab4jea #aab4jeh #aaa4gga #aaa4ggh ,v #a4gdddg #a4aafea #aab4jai #aab4jbf #aaa4gci #aaa4gdf ------- ------- ------- ------- ,mean1 #aab4jbe #aab4jcb #aaa4gde #aaa4geb ,maximum1 #aab4jea #aab4jeh #aaa4gga #aaa4ggh ,minimum1 #aaa4iha #aaa4ihh #aaa4gja #aaa4gjh ,difference1 4#jgj 4#jgj 4#jgj 4#jgj ,the values assigned to carbon in the last two columns were found thus-- ,when ,o #af1 ,c #ab4jja1 when ,o #ae4if1 ,c #aa4iga4 0 ,o #af1 ,c #ab4jjc1 0 ,o #ae4if1 ,c #aa4igc4 ,calculating the atomic weight directly from all the oxalate used and oxide found it would give3 ,at4 ,wt4 ,cd4 ,at4 ,wt4 ,cd4 ,at4 ,wt4 ,cd4 ,at4 ,wt4 ,cd4 7,o #af7 7,o #af7 7,o #ae4if7 7,o #ae4if7 7,c #ab4jja7 7,c #ab4jjc7 7,c #aa4iga7 7,c #aa4igc7 #aab4jbe4 #aab4jcb4 #aaa4gde4 #aaa4geb4 ,there seems about equal evidence for the two values assigned to carbon when oxygen #af4 ,the value of cadmium as given by this method is therefore #aab4jbe or #aab4jcb4 ,as will be seen at a glance this figure agrees much more closely with that of ,lenssen than with that of ,partridge4 ,lenssen ,partridge ,my work #aab4jdc4 #aaa4haf4 #aab4jbe or #aab4jcb4 ,it also agrees fairly well with the figure #aab4jgjf which ,i obtained by the first method described4 ,advantages of the ,method4 ,the method possesses no advantage whatever over the one which involves starting with the element itself4 ,the oxalate can however be obtained pure having pure metal4 ,the salt is of definite composition when perfectly dry4 ,the method as carried out avoided the contact of any foreign material with the salt after it was weighed4 ,disadvantages of the ,method4 #a ,the avidity with which the dried oxalate takes up moisture from the air is an objection to its use for the determination of atomic weights4 ,even with the greatest care there is a slight element of uncertainty introduced from this source4 #b ,the oxalate is stated to decompose into a mixture of the oxide and metal4 ,the temperature required for this decomposition is somewhat higher than the melting point of cadmium4 ,the metal heated above its melting point possesses a vapor-tension and loss in weight must result1 whatever precaution is taken in heating4 ,this is the probable explanation why the results obtained by this method are lower than those of the preceding4 ,a comparison of the two methods leads me to attach much more importance to the results of that one which establishes the relation between cadmium and cadmium oxide directly and ,i therefore regard the atomic weight of cadmium as very closely expressed by the figure #aab4jg when oxygen #af4 ,preparation of ,certain ,sub-compounds of ,cadmium4 ,historical4 ,cadmium acts so generally as a bivalent element that it is usually regarded as entering into combination only where it can play this rle4 ,the only compound described1 in which it has apparently a lower valence than two1 was prepared by ,marchand#aj4 ,it was obtained by heating cadmium oxalate to the melting point of lead when a green powder remained behind which resembled chromium oxide4 ,when heated on the air it appeared to be decomposed into metal and oxide4 ,when treated with mercury the compound was not altered4 ,an analysis showed it to have the composition represented by the formula ,cd,o4 #aj ,pogg4 ,ann4 ,,xxxviii1 #adc4 ,a4 ,vogel#aa has shown that the green powder described by ,marchand consists of a mixture of the metal and oxide4 ,when this mixture is treated with dilute acetic acid the metal remains behind as microscopic glistening globules4 ,the lower the temperature at which the oxalate is decomposed the more oxide and the less metal were found in the product4 ,there was then no compound known in which cadmium acted as if its valence was less than two when this work was undertaken4 ,that it may act with a greater valence was shown by ,r4 ,haafs#ab4 ,he found that when zinc hydroxide was treated with hydrogen dioxide certain compounds of zinc and oxygen were formed containing more oxygen than the normal oxide ,zn,o4 ,the close resemblance between zinc and cadmium led him to try the same reaction with cadmium4 ,hydrogen dioxide was accordingly allowed to act on cadmium hydroxide and the resulting product analyzed4 ,there were formed ,cd,o1 ,cd,o and ,cd,o4 ,in no case was the compound ,cd,o obtained4 ,these compounds are described as fairly stable even at a hundred degrees4 #aa ,jahrb4 #ahee1 #cij4 #ab ,ber4 #ahhd1 #bbdi4 ,the ,preparation of ,cd,cl4 ,when anhydrous cadmium chloride is heated with metallic cadmium in a vacuum1 or in an atmosphere of nitrogen1 to the fusing point of the chloride1 the molten chloride quickly assumes a garnet red color4 ,in order to investigate this phenomenon a quantity of the chloride was prepared by dissolving the redistilled metal in an excess of hydrochloric acid1 evaporating the chloride to dryness on a water bath1 and finally removing the water of crystallization by heating in a current of dry hydrochloric acid gas4 ,the heating was effected by placing the chloride in a long platinum boat1 which was shoved into a large glass tube1 through which was passed a current of the acid gas4 ,the tube was heated by means of a combustion furnace and the chloride kept in the molten condition for two or three hours4 ,by this means a perfectly white crystalline chloride of the composition ,cd,cl was obtained1 free from water or oxychloride4 ,the chloride and an excess of metal were placed in a long-necked flask of hard glass and after the displacement of the air by nitrogen1 heated to the melting point of the chloride4 ,the liquid chloride attained its maximum depth of color in a few minutes1 nevertheless the heating was continued for five hours4 ,when the temperature was allowed to rise much above the melting point of the chloride the red substance underwent decomposition and globules of metal collected upon the walls of the flask4 ,for this reason no more heat was applied than was just necessary to keep the contents of the flask in a liquid condition4 ,during the very gradual cooling of the flask it was shaken gently in order to facilitate the sinking of any metal1 which might be mechanically retained by the chloride4 ,on cooling1 the solidified mass possesses a slightly greenish tint which disappeared when cold1 the substance having then a grayish white color and a cleavage resembling that of talc or brucite4 ,when examined under the microscope it was found to be perfectly homogeneous and free from metal4 ,it gave no metallic streak when rubbed between agate surfaces4 ,an analysis of the first preparation showed the following composition2 ,amount of chloride used 4#cceda gr4 0 0 cadmium found 4#baeei 0 0 0 chlorine 0 4#aaidc 0 ,cadmium4 ,chlorine4 #fd4bg per cent4 #ce4fa per cent4 ,these proportions are nearly those of a compound having the composition ,cd,cl1 in which the calculated percentages are3 ,cadmium4 ,chlorine4 #fd4cd #ce4ff 7,foot note74 ,in the paper in the ,american ,chemical ,journal ,,xii1 #dhh1 which records this work the analyses and percentages were calculated on the basis of the atomic weight of cadmium #aaa4g4 ,although my work since this date has shown that #aab4jg is the true value1 yet ,i think it preferable to use the old number here since the changes to be introduced would be very slight and the same results are thereby kept uniform in the two publications4 ,in order to determine whether the close approximation to definite atomic proportions might not be accidental1 the material was reheated with an excess of the metal for twenty hours4 ,the product was analyzed4 ,amount of chloride used #a4deigj gr4 0 0 cadmium found 4#icijd 0 0 0 chlorine 0 4#ebcbi 0 ,cadmium4 ,chlorine4 #fd4cc per cent4 #ce4he per cent4 ,a second preparation of the substance was made in all respects like the first4 ,two analyses were made4 ,first ,analysis3 ,amount of chloride used 4#fajaj gr4 0 0 cadmium found 4#cibce 0 0 0 chlorine 0 4#bagbe 0 ,cadmium4 ,chlorine4 #fd4ca per cent4 #ce4fa per cent4 ,second ,analysis3 ,amount of chloride used 4#bjfaf gr4 0 0 cadmium found 4#acbff 0 0 0 chlorine 0 4#jgceb 0 ,cadmium4 ,chlorine4 #fd4ce per cent4 #ce4ff per cent4 ,a third preparation was made like the first and second and analyzed4 ,analysis3 ,amount of chloride used 4#bhcb gr4 0 0 cadmium found 4#ahbdd 0 0 0 chlorine 0 4#ajabc 0 ,cadmium4 ,chlorine4 #fd4db per cent4 #ce4gd per cent4 ,when the new substance is heated it fuses to a red liquid and then breaks up into metal and the chloride of cadmium4 ,its reactions are in general those of a strong reducing agent4 ,treated with nitric acid1 oxides of nitrogen are liberated4 ,with dilute hydrochloric1 sulphuric and acetic acids it gives free hydrogen4 ,in the presence of dilute acids it reduces mercuric to mercurous chloride1 or to metallic mercury4 ,three determinations of the reducing power of the substance were made with a freshly prepared specimen1 by dissolving weighed portions in hydrochloric acid and measuring the hydrogen liberated4 ,the following results were obtained3 ,hydrogen found4 ,hydrogen calculated for ,cd,cl4 #a determination #ae4fg c4c4 #ae4fe c4c4 #b 0 #aa4hj c4c4 #aa4hb c4c4 #c 0 #bc4jj c4c4 #bc4jc c4c4 ,an examination of the analyses shows beyond question that the substance formed by the action of metallic cadmium on the molten anhydrous chloride is of definite composition4 ,the proportion of cadmium to chlorine could not be changed even when the substance was heated with the metal for twenty hours1 while a very short time was sufficient for its formation when the metal and chloride were melted together4 ,it may be possible that a substance possessing these properties is not a definite chemical compound but a mixture of cadmous and cadmic chlorides or a solution of one in the other4 ,if it were a solution it is difficult to see why the composition of the solution should be so constant1 since the solubility of a substance is generally altered by a change in temperature4 ,the different preparations were not made at exactly the same temperature yet the composition of the different preparations was the same4 ,if the substance was a mixture of the two chlorides1 when treated with water the cadmic chloride would most probably dissolve directly leaving the cadmous chloride to be acted upon by the water4 ,the decomposition by water will however be seen not to be as simple as would be expected under these conditions4 ,from the above considerations it appears highly probable that the substance is a definite chemical compound of cadmic and cadmous chlorides4 ,if cadmic chloride can form a chemical compound with the chloride of another element there appears to be no reason why it should not form a compound with another chloride of cadmium1 as with cadmous chloride4 ,the preparation of ,cd,br4 ,the anhydrous bromide of cadmium was prepared by dissolving the carbonate in an aqueous solution of hydrobromic acid1 evaporating the bromide to dryness on the water bath and heating the residue in a current of dry hydrobromic acid gas4 ,when the bromide was heated with an excess of the metal in an atmosphere of nitrogen it conducted itself in general like the chloride4 ,when the molten bromide and the metal came in contact the salt quickly became deep red in color4 ,after heating for some time considerable dissociation was produced by raising the temperature4 ,this was more apparent in the preparation of the bromide than with the chloride4 ,on cooling1 the mass possessed a greenish tint which disappeared when cold1 the bromide then being very nearly the same color as the corresponding chloride4 ,also like the chloride it appeared to be homogeneous and free from metal4 ,two determinations of cadmium and two of bromine were made1 using the product as soon as prepared4 ,first determination of cadmium3 ,amount of substance used 4#cgcf gr4 0 0 cadmium found 4#affeh 0 ,cadmium4 #dd4ei per cent4 ,second determination of cadmium3 ,amount of substance used 4#ceicj gr4 0 0 cadmium found 4#afjac 0 ,cadmium4 #dd4eg per cent4 ,first determination of bromine3 ,amount of substance used 4#fffdj gr4 0 0 bromine found 4#cfiec 0 ,bromine4 #ee4de per cent4 ,second determination of bromine3 ,amount of substance used 4#efjce gr4 0 0 bromine found 4#cajhe 0 ,bromine4 #ee4dg per cent4 ,the percentage of cadmium and bromine found agrees very closely with that of a compound of the formula ,cd,br4 ,the relation of cadmium to bromine in this would be3 ,cadmium4 ,bromine4 #dd4dd per cent4 #ee4ef per cent4 ,when this compound was heated for a long time with an excess of the metal its composition was not appreciably changed4 ,the compound ,cd,br is a strong reducing agent3 giving with nitric acid oxides of nitrogen1 with dilute hydrochloric1 sulphuric or acetic acid1 free hydrogen1 and with mercuric chloride1 mercurous chloride or metallic mercury4 ,the action of water on the bromide by means of which cadmous hydroxide was formed1 was not studied as carefully as with the chloride but appeared to be essentially the same4 ,the ,preparation of ,cd,i4 ,cadmic iodide was prepared in the same manner as the bromide4 ,it was dried in a stream of hydriodic acid gas at as low temperature as possible to lessen the decomposition of the hydriodic acid4 ,when the anhydrous iodide was heated with an excess of metal in an atmosphere of nitrogen the red color of the iodide became intensified4 ,heating was continued until there was evidence of dissociation1 which1 under the same conditions1 was less marked than with the chloride and much less than with the bromide4 ,owing to the high specific gravity of the iodine compound some difficulty was experienced in obtaining a preparation free from metal4 ,this difficulty was finally overcome by keeping the material just above its melting temperature for a long time and constantly jarring the flask4 ,during the process of cooling a decidedly greenish tint was observed which disappeared as the process was continued4 ,when cold the substance resembled the chloride and bromide4 ,two determinations of cadmium were made in the first preparation4 ,first determination3 ,amount of substance used 4#eeedj gr4 0 0 cadmium found 4#agdef 0 ,cadmium4 #ca4dc per cent4 ,second determination3 ,amount of substance used 4#dgece gr4 0 0 cadmium found 4#adihj 0 ,cadmium4 #ca4ea per cent4 ,as these results did not correspond to the composition represented by the formula ,cd,i1 which our experience with the chloride and bromide had led us to expect1 we reheated the material for several hours with an excess of the metal4 ,two analyses of the product gave3 ,cadmium4 ,iodine4 #ca4dd per cent4 #fh4fe per cent4 #ca4ci #fh4fh showing that the iodide had taken up during the first heating all the metal which it could retain4 ,the analytical results suggest the formula ,cd,i1 in which the calculated percentages are3 ,cadmium4 ,iodine4 #ca4ec per cent4 #fh4dg per cent4 ,in its conduct towards dilute hydrochloric and acetic acids and water the substance behaves like the corresponding chloride and bromide4 ,the ,preparation of ,cadmous ,hydroxide and ,oxide4 ,when the substance ,cd,i is treated with water a complicated reaction takes place4 ,the general character of the reaction appears to be the same with the chloride1 bromide and iodide4 ,the decomposition of the chloride was studied more thoroughly than that of the other compounds4 ,when the finely powdered chloride is treated with water it yields cadmic chloride which passes into solution1 a small quantity of a white flocculent material which may be cadmic hydroxide but which in no case could be entirely freed from traces of chlorine1 and a highly lustrous crystalline substance which rapidly lost its crystalline appearance and passed over into a grayish white amorphous compound1 which when freed from chlorine was found to be cadmous hydroxide1 of the formula ,cd7,,oh74 ,the separate products resulting from the treatment with water were analyzed4 ,first ,analysis3 ,amount of ,cd,cl treated with water #a4deigj gr4 ,cadmium found in flocculent precipitate 4#jbcah 0 0 0 0 crystalline substance 4#jifad 0 0 0 0 solution in water 4#haigj 0 ,total cadmium found 4#icijb 0 ,chlorine found in crystalline compound 4#jjcga gr4 0 0 0 solution in water 4#eafga 0 ,total chlorine found 4#ebjdb 0 ,approximately seven-eighths of the total cadmium dissolved as cadmic chloride while the remainder was contained in the flocculent precipitate and in the gray crystalline compound4 ,second ,analysis3 ,amount of ,cd,cl treated with water #a4jgid gr4 ,cadmium found in flocculent precipitate 4#jadfi 0 0 0 0 solution in water 4#fjgie 0 ,chlorine found in solution in water 4#chdia 0 ,the percentage of cadmium in the white precipitate is less in this analysis than in the former4 ,the cadmium in solution is again about seven-eighths of the total and the chlorine present in the same solution shows that the cadmium was all combined as cadmic chloride4 ,all attempts to determine the composition of the gray crystalline compound failed1 owing to the rapidity with which it decomposed with water4 ,even with the most rapid work it could not be isolated in the undecomposed condition4 ,analyses of the partially decomposed crystals gave variable proportions of metal and halogen but never less than eight equivalents of the former to one of the latter4 ,while the decomposition of ,cd,cl with water cannot at present be fully explained1 yet it is clear from the analyses that one eighth of the total cadmium is thrown down as a white precipitate and a crystalline compound which as will be seen passes over into cadmous hydroxide4 ,one half of the cadmous chloride is oxidized to cadmic chloride taking the chlorine from the other half4 ,the compound ,cd,cl was treated directly with absolute alcohol with the hope of obtaining the crystalline substance in an undecomposed condition4 ,although a substance of the same general appearance as that formed in the presence of water was obtained yet it decomposed so readily that a satisfactory analysis could not be made4 ,notwithstanding the rapidity with which the decomposition of the crystalline compound begins1 long continued washing was necessary in order to completely remove the chlorine4 ,the extraction of the last traces of the halogen is hastened by the use of warm instead of cold water4 ,the temperature of the water must not exceed #ej;,c4 ,in water whose temperature approaches the boiling point the hydroxide is slowly decomposed with liberation of metal4 ,the new hydroxide is a strong reducing agent4 ,it dissolves in dilute acids2 yielding with nitric acid oxides of nitrogen1 with hydrochloric or sulphuric acid free hydrogen4 ,after washing with warm water until all the chlorine had disappeared1 it was dried over phosphorus pentoxide and analyzed4 ,first determination of cadmium4 ,amount of substance used 4#jifh gr4 0 0 cadmium found 4#jhdae 0 ,cadmium4 #hf4ic per cent4 ,second determination of cadmium4 ,amount of substance used 4#jihjf gr4 0 0 cadmium found 4#jhebb 0 ,cadmium4 #hf4ia per cent4 ,the calculated percentage of cadmium in ,cd7,,oh7 is3 ,cadmium4 #hf4gi per cent4 ,the determination of water in cadmous hydroxide was made by placing a small specimen tube containing the hydroxide in a ,kjeldahl flask which was heated in a bath of concentrated sulphuric acid4 ,during the heating a slow current of dry nitrogen was passed over the substance4 ,first determination of water4 ,amount of substance used 4#jhdcd gr4 0 0 water found 4#jjfji 0 ,water4 #g4bb per cent4 ,second determination of water4 ,amount of substance used 4#jhhie gr4 0 0 water found 4#jjfjj 0 ,water4 #f4gd per cent4 ,third determination of water4 ,amount of substance used 4#aagff gr4 0 0 water found 4#jjhef 0 ,water4 #g4be per cent4 ,average amount of water #g4jg per cent4 ,the calculated percentage of water in ,cd7,,oh7 is1 #f4ii4 ,at the temperature at which concentrated sulphuric acid gives off dense white fumes cadmous hydroxide gives off all its water and passes over into a heavy yellow powder4 ,at #aej;,c not a trace of water was liberated4 ,under the microscope the yellow powder was found to consist of minute translucent crystals4 ,first determination of cadmium4 ,amount of substance used 4#jhjfd gr4 0 0 cadmium found 4#jgeaa 0 ,cadmium4 #ic4ad per cent4 ,second determination of cadmium4 ,amount of substance used 4#ajhdf gr4 0 0 cadmium found 4#ajajf 0 ,cadmium4 #ic4ag per cent4 ,the calculated percentage of metal in ,cd,o is #ic4cb per cent4 ,if water of too high temperature is employed in washing the subhydroxide1 the presence of free metal in it can be detected under the microscope and by rubbing between agate surfaces4 ,if the yellow suboxide is strongly heated it breaks up into a mixture of oxide and metal which possesses a distinctly green color4 ,towards acids the suboxide conducts itself like the subhydroxide4 ,it is a fact of some interest in connection with the periodic arrangement of the elements1 that the tendency toward the formation of a lower series of compounds which becomes so strongly developed in mercury begins to exhibit itself in some slight degree in cadmium4 ,notes on ,crystals of ,metallic ,cadmium4 ,the measurements of the cadmium crystals were made by ,dr4 ,williams who has very kindly furnished me with his results4 ,no reliable crystallographic description of the element cadmium seems thus far to have appeared--a fact due to the difficulty in obtaining suitable material4 ,the crystals examined1 although not capable of yielding entirely satisfactory results are nevertheless such as to make them of interest4 ,in #aheb ,g4 ,rose noted the fact that distilled cadmium collected at the neck of the retort in drops which solidified as complex polyhedral aggregates#ac similar to those formed by zinc#ad4 ,in #ahgd ,kammerer encountered the same aggregates which he explained as complicated isometric combinations#ae4 ,this opinion was cited in #ahha by ,rammelsberg#af4 ,in #ahhd ,brgger and ,flink stated that in their opinion zinc1 magnesium and probably cadmium were from analogy with beryllium which they had studied1 hexagonal and holohedral4#ag #ac ,pogg4 ,ann4 #he1 #bic4 #ad ,amer4 ,chem4 ,journ4 #aa1 #bai4 #ae ,ber4 d4 deutch4 ,chem4 ,gesell4 #ahgd1 #agbd4 #af ,handb4 d4 krystallographisch physicalischen ,chemie4 ,i1 #ahd4 #ag ,zeits amp2 ,kryst4 #i1 #bcf4 ,this supposition has already been substantiated in the case of the two former elements#ah while the present material leads to the same result for the last named4 ,the cadmium crystals were produced in the same manner as were those of zinc and magnesium measured before1 viz2 by distillation in a vacuum4 ,the appearance of the tubes thus obtained was closely like that in the other cases4 #ah ,amer4 ,chem4 ,journ4 #aa1 #bbe and ,ibid4 #ab1 #bbe4 ,the polyhedral aggregates were abundant and reached considerable dimensions4 ,the crystallizing power of the cadmium however1 seems to be less1 so that the only crystals suitable for measurement were extremely minute4 ,the largest individuals were barrel-shaped1 like those of zinc and resembled little piles of basal plates4 ,their side planes are not infrequently uneven and bent1 probably as the result of the softness and great ductility of the metal4 ,only the most minute crystals show pyramidal planes of comparative perfection4 ,these are well suited for a microscopic examination1 but their small size renders their measurement on a reflecting goniometer a matter of difficulty4 ,after a careful search two crystals were secured which1 although they had a diameter of only one third of a millimeter1 from their microscopic appearances promised good results4 ,their planes however were found to give compound reflections and a somewhat disappointing variation in corresponding angles4 ,on the best crystal three zones were measured as follows3 7normal angles7 ,zone ,i ,zone ,,ii ,zone ,,iii #jjja 3 #jaa #fb #ce #jjja 3 #aja #fb #d #jjja 3 #aja #fb #bi #jjja 3 #jaj #hi #ej #jjja 3 #ja #aah #eg #jjja 3 #aj #aah #bh ,the second crystal was much less satisfactory1 since values for the angle between the base and pyramid 7#jjja73 7#jaa7 were obtained which varied all the way from #fa #b to #fc #dc4 ,these measurements must therefore be regarded as of little or no value4 ,if we average the readings for this angle on the first crystal we obtain #fb #bc1 from which a 3 c #a 3 #a4feed4 ,a comparison of the axial ratios of the four rhombohedral and four holohedral hexagonal elements gives the following3 ,bismuth a 3 c #a 3 #a4cjce 7,g4 ,rose1 #ahdi74 ,rhombo- ,antimony a 3 c #a 3 #a4cbce 7,laspeyres1 #ahge74 hedral4 ,tellurium a 3 c #a 3 #a4cbih 7,g4 ,rose1 #ahdi74 ,arsenic a 3 c #a 3 #a4djbe 7,zepharovich1 #ahge74 ,zinc a 3 c #a 3 #a4cefdbe 7,williams and ,burton1 #ahhi74 ,holohedral4 ,beryllium a 3 c #a 3 #a4ehjb 7,brgger1 #ahhd74 ,magnesium a 3 c #a 3 #a4fbjb 7,williams1 #ahij74 ,cadmium a 3 c #a 3 #a4feed 7,williams1 #ahia74 ,zinc appears from its axial ratio to belong rather to the rhombohedral group and this is the only one of the last four elements upon which the faintest indication of any divergence from a holohedral development of all of its forms has been observed4 ,on crystals of this substance there is an occasional rhombohedral alternative of the faces of certain of the pyramids1 although the crystals otherwise appear to be holohedral4#ai ,the crystals of cadmium like those of magnesium show only the three forms ,,op 7#jjja71 ,p 7#aja71 and ,p 7#ajj74 ,brgger and ,flink observed on beryllium the additional forms ,p 7#bj7 and ,p 7#bjba72 while upon zinc a large number of forms in the zone of the unit pyramid occur4 #ai ,amer4 ,chem4 ,journ4 #aa1 #bbd4 pl4 #b fig4 #h4 ,not infrequently the cadmium crystals show a tendency toward a hemimorphic development4 ,this is plainly seen when a large number of them are examined together under the microscope4 ,the little barrel-shaped crystals are mostly attached by their sides and yet one of their ends is often broader than the other4 ,sometimes they taper nearly to a point1 quite like greenockite crystals4 ,the ,cohesion ,phenomena of ,cadmium4 ,the cohesion phenomena of cadmium are similar to those of zinc but are still more striking4 ,when a crystal is sharply focused under the microscope and then gently pressed on the side with the point of a needle an unbroken pyramidal face is seen to suddenly become striated parallel to the basal plane1 as though a gliding in the basal section took place4 ,some of these crystals were kindly examined by ,prof4 ,otto ,mgge of ,mnster1 ,germany1 who has added so much to our knowledge of the cohesion phenomena in crystals4 ,he has written in regard to his observations as follows2 8,the cadmium crystals as far as their gliding phenomena are concerned behave quite like zinc4 ,if a crystal is carefully loosened and then squeezed with a pair of pincers it is easy to see that the smooth surface where it was attached to the glass became striated parallel to ,,op 7#jjja7 and that at the same time two other sets of striations are produced which meet at an angle of about #he and intersect the trace of the basal plane at about #dg4 ,the plane of attachment was selected for observation because it was smoother than the pyramidal faces4 ,in the above case this plane has the position of a steep pyramid inclined to the base at an angle of about #ajj4 ,the oblique sets of striations appear to represent gliding planes parallel to the unit pyramid faces 7#b,p 7#ajb7 of ,rose7 as in the case with zinc4 ,whether the horizontal striations were due to gliding parallel to the base ,i could not certainly decide4 ,many of the crystals appear when pinched to be completely overturned1 in which cases ordinary bending accompanies gliding as in the case of gold set4 ,this is shown by the fact that both faces and striations become rounded40 ,biographical ,sketch4 ,harry ,clary ,jones was born near ,new ,london1 ,frederick ,county1 ,maryland1 ,nov4 #aa #ahfe4 ,after attending several schools in that state he entered the ,johns ,hopkins ,university in the autumn of #ahhe as a special student of chemistry and physics4 ,he matriculated in #ahhg and received the degree of ,bachelor of ,arts in #ahhi1 having held an ordinary and an honorary scholarship4 ,for the last three years he has continued his studies in the ,university following chemistry as a principal subject and mineralogy and geology as subordinates4 ,during this time he has been appointed twice to a university scholarship1 was lecture assistant to professor ,remsen1#ij-ia1 and ,fellow in chemistry1#ia-ib4