,transcriber ,note ,text emphasis is denoted as ,italic and ,bold4 ,whole and fractional parts of numbers as #abc-d_/e4 ,,humphrey',s ,,journal ,,of ,,the ,,daguerreotype ,,and ,,photographic ,,arts4 ,the above-named ,publication is well known as the best and most valuable one devoted to the ,photographic ,science in this country4 ,humphrey's ,journal made its first appearance ,nov4 #ast1 #ahej1 and consequently is the first and oldest serial offered to the ,photographic world4 ,the art of producing ,portraits and ,landscapes by means of ,light has recently taken a new and enlivening impulse1 which will in all probability lead to important and interesting results4 ,no practical ,daguerreotypist1 ,photographer1 or amateur should be without the means at hand for securing all of the information upon this subject4 ,each should be ready to receive and apply the improvements as they may be developed4 ,in order to accomplish this1 it is a matter of great importance to the ,practitioner or ,experimenter that he should have a reliable medium through which he can obtain information4 ,in what source can the inquirer better place his confidence than in a regular ,journal1 whose editor is literally a practical person1 and familiar with the manipulations necessary for producing ,portraits upon ,daguerreotype ,plates1 and upon glass and paper8 ,such is the conductor of ,humphrey's ,journal4 ,this ,journal is published once every two weeks1 and contains all the improvements relating to the ,art1 and is the only ,american ,journal whose editor is practically acquainted with the process for producing ,daguerreotypes4 ,ambrotypes1 and ,photographs ,the first ,no4 of ,vol4 ,,viii is dated ,may #ast1 #ahef4 ,the terms 7,two ,dollars per annum7 are trifling compared with the vast amount of information furnished4 ,there are several societies recently established in ,europe composed of learned and scientific men1 who are in every way engaged in investigating the ,science1 and we may look for improvement from that quarter1 as well as from our numerous resources at home4 ,in the former case our facilities for early and reliable information cannot well be surpassed4 ,ambrotypes4--,humphrey's ,journal contains everything novel which appears upon this subject1 and has already presented more new1 important2 and original matter than can be found in any other place4 ,many are the letters we have received during the term of the last volume1 in which the writer has stated that a single number of ,humphrey's ,journal has contained information of more value to him than several times the amount paid for the entire volume4 ,our resources have grown up around us1 and our facilities for procuring1 as well as distributing1 all such facts and improvements as will benefit as well as instruct all who have the progress of the ,art at heart1 are as ample as they can well be made4 ,the future volumes will be abundantly furnished with original writings from persons of standing in the scientific world2 and the practical ,photographer will here find a full account of such improvements as may from time to time develope themselves4 ,from the ,editor's long practical experience in the ,heliographic ,science1 he will be enabled to present the subject in a plain1 clear and concise manner4 ,read what the ,editors say of ,humphrey's ,journal3-- ,we have received a copy of a valuable ,journal 7,humphrey's7 published in ,new ,york1 which has reached the #ahth number of ,vol4 ,,vi4 444 ,we now have the pleasure of quoting from our transatlantic coadjutor4--,liverpool ,photographic ,jour4 ,humphrey's ,journal is practical as ,well as scientific in character4--,american ,journal of ,science and ,arts4 ,it treats the subject knowingly1 and with force4--,new ,york ,tribune4 ,it is both a popular and interesting publication4--,mechanics' ,magazine4 ,it is highly useful to all who practice 'shadow catching4'--,ohio ,state ,journal4 ,the work is neatly gotten up1 and contains many interesting varieties in this new field of science4--,times4 ,it should be hailed and encouraged1 not only by ,daguerreotypists themselves1 but by every lover of ,science and ,art4--,the ,democrat4 ,we cannot too strongly urge all artists1 and those persons who feel an interest in the ,heliographic ,arts and ,sciences1 to take a copy of the work4--,sentinel4 ,it is indicative of talent worthy of the important ,art it is designed to elevate4--,american4 ,this ,art is entitled to its own organ1 which could not have fallen into better hands than those of the editor of ,humphrey's ,journal4--,transcript4 ,it is a scientific work of interest and usefulness4--,star of the ,north4 ,this ,journal answers many points heretofore regarded as inexplicable4--,hudson ,river ,chronicle4 ,it is rich with interest4--,north ,american4 ,it contains all the ',improvements4'--,delta4 ,it teaches us how to take our own portraits4--,bee4 ,it will cultivate a taste for ,daguerreotypes4--,commercial ,advertiser4 ,it should be in the hands of all4--,reveille4 ,it is the ,daguerreotypist's friend4--,london ,news4 ,it should be found in every library4--,evening ,journal4 ,from some of our old subscribers4 ,humphrey's ,journal has been the means of saving much time and money1 for by its instruction ,i have been enabled to produce some of the finest ,paper ,pictures ,i have ever seen4 ,w4 ,p4 ,don't fail to send me the ,journal1 for ,i would not be without it for five times the amount of subscription4 ,it is the only publication ,i can depend upon4 ,a4 ,g4 ,r4 ,your treatment of the humbugs and humbugging members of the profession1 is of the most valuable importance to us practical ,daguerreians4 ,go on4 ,god speed6 ,here is the amount for the renewal of my subscription4 ,e4 ,f4 ,s4 ,how can any ,operator afford to be without it8 ,l4 ,l4 ,h4 ,here is five dollars3 send me ,humphrey's ,journal to this amount4 ,i will not be without it4 ,m4 ,s4 ,it is my best friend4 ,j4 ,e4 ,w4 ,we might quote like commendatory extracts enough to more than ten times fill this page4 ,humphrey's ,journal contains #af octavo pages of reading matter4 ,,terms4 ,one copy per annum1 in advance #b #jj ,three copies1 do4 do4 #e #jj ,six copies1 do4 do4 #i #jj ,the thousands who read it cannot be induced to remain without it4 ,all who desire to keep up with the improvements should subscribe for a copy4 ,subscription price ,two ,dollars per year4 ,don't fail to become a subscriber4 ,address ,s4 ,d1 ,,humphrey1 ,,new ,,york4 ,office1 #cg ,lispenard ,street ,a ,,practical ,,manual ,,of ,,the ,,collodion ,,process1 ,,giving ,,in ,,detail ,a ,,method ,,for ,,producing ,,positive ,,and ,,negative ,pictures on ,glass and ,paper4 ,,ambrotypes4 ,,printing ,,process4 ,,also1 ,,patents ,,for ,,the ,,collodion ,,processes2 ,,melainotypes--,,photographs ,,in ,,oil--,,albumenized ,,collodion--,,cutting',s ,,patents ,,and ,,correspondence4--,,specification',s ,,of ,,all ,,the ,,foregoing1 ,,giving ,,each ,,process ,,entire4 ,,third ,,edition1 ,,revised ,,and ,,greatly ,,enlarged4 ,by ,s4 ,d4 ,,humphrey4 ,,new ,,york3 ,,humphrey',s ,,journal ,,print1 #cg ,,lispenard ,,street4 #aheg4 ,entered according to ,act of ,congress1 in the year #aheg1 by ,s4 ,d4 ,,humphrey1 ,in the ,clerk's ,office of the ,district ,court of the ,united ,states for the ,southern ,district of ,new ,york4 ,,preface ,,to ,,the ,,third ,,edition4 ,the rapid and unexpected sale of the entire second edition of this ,manual has induced the author to lay the ,third ,edition before the ,public4 ,although but little time has elapsed since the second1 yet there have been some new developments which it has been thought best to give1 as conducive to the interests of the practitioner4 ,the manipulations have been given somewhat more in detail than in the ,second ,edition4 ,all that would have a tendency to confuse the reader has been carefully avoided1 and only the plain methods for operating laid down4 ,the work is intended for the beginner in the glass process of producing ,heliographic pictures4 ,s4 ,d4 ,h4 ,new ,york1 ,february #ast1 #aheg4 ,,preface ,,to ,,the ,,first ,,edition4 ,the object of this little ,manual is to present1 in as plain1 clear and concise a manner as possible1 the practice of a ,collodion ,process4 ,this beautiful acquisition to a sun-pencilling was first given to the public by ,mr4 ,frederick ,scott ,archer1 an ,english gentleman1 who alone is entitled to the credit1 and deserves the esteem of every lover and practitioner of the ,art1 for his liberality in giving it to the world4 ,the ,process here presented has never before appeared in print1 and has been practised with the most eminent success by those who have been enabled to adopt it4 ,all reference to the various systems or methods of manipulation1 by the thousands of practitioners1 has been excluded1 and one ,process given4 ,i conceived that this was the better plan to adopt1 thus leaving the mind of the learner free from confusion1 and pointing out one course1 which1 if carefully followed1 will produce good and pleasing results4 ,i have also presented a list of all ,patents upon the ,collodion ,process2 this will give all an opportunity of choosing their own course in regard to the respect they may conceive to be due to such ,patent ,rights4 ,s4 ,d4 ,h4 ,,contents4 ,,part ,i4 ,,chapter ,i4 ,introduction--,light--,solar ,spectrum--,decomposition of ,light--,light--,heat and ,actinism--,blue ,paper and ,color for the ,walls of the ,operating ,room--,proportions of ,light1 ,heat and ,actinism composing a ,sunbeam--,refraction--,reflection--,len ses--,copying--,spherical ,aberration--,chromatic ,aberration #ac ,,chapter ,,ii4 ,camera--,arrangement of ,lenses--,camera ,tubes--,camera ,boxes1 ,bellows1 and ,copying--,camera ,stands--,head ,rests--,cleaning ,vice--,nitrate ,bath--,leveling ,stands--,printing ,frames--,collodion ,vials #bf ,,part ,,ii4 ,practical ,hints on ,photographic ,chemistry4 ,,chapter ,,iii4 ,soluble ,cotton--,manipulation--,plain ,collodion--,bromo-,iodized ,collodion for ,positives--,ditto for ,negatives--,solution of ,bromide and ,iodide of ,potassium and ,silver--,double ,iodide of ,potassium and ,silver--,developing ,solution--,fixing the ,solution--,brightening and ,finishing the ,image--,photographic ,chemicals #da ,,part ,,iii4 ,practical ,details of the ,positive or ,ambrotype ,process4 ,,chapter ,,iv4 ,lewis's ,patent ,vices for ,holding the ,glass--,cleaning and ,drying the ,glass--,coating--,exposure in the ,camera--,developing--,fixing or ,brightening--,backing up1 c4 #abi ,,part ,,iv4 ,practical ,details of the ,negative ,process4 ,,chapter ,v4 ,negative ,process--,soluble ,cotton--,plain ,collodion--,developing ,solution--,re-,developing ,solution--,fixing the ,image--,finishing the ,image--,nitrate of ,silver ,bath #adc ,,part ,v4 ,practical ,details of the ,printing ,process4 ,,chapter ,,vi4 ,printing ,process--,salting ,paper--,silvering ,paper--,printing the ,positive--,fixing and ,coloring ,bath--,mounting the ,positive--,facts worth ,knowing #aea ,,chapter ,,vii4 ,helio ,process4--,an ,entire ,process for ,producing ,collodion ,positives and ,negatives with one ,bath1 and in much less time than by any other known ,process3 by ,helio--,photographic ,patents #afd ,,chapter ,,viii4 ,the ,collodio-,albumen ,process in ,detail #aij ,,chapter ,,ix4 ,on a ,mode of ,printing ,enlarged and ,reduced ,positives1 ,transparencies1 c41 from ,collodion ,negatives--,on the ,use of ,alcohol for ,sensitizing ,paper--,recovery of ,silver from ,waste ,solutions1--from the ,black ,deposit of ,hypo ,baths1 c4--,the ,salting and ,albumenizing ,paper--,on the ,use of ,test ,papers--,comparison of ,british and ,french ,weights and ,measures #aia ,,chapter ,i4 ,,light--,,solar ,,spectrum--,,decomposition ,,of ,,light--,,light1 ,,heat ,,and ,,actinism--,,blue ,,paper ,,and ,,color ,,for ,,the ,,walls ,,of ,,the ,,operating ,,room--,,proportions ,,of ,,light1 ,,heat ,,and ,,actinism1 ,,composing ,a ,,sun-,,beam--,,refraction--,,reflection --,,lenses--,,copying--,,spherical ,,aberration--,,chromatic ,,aberration4 ,it has been well observed by an able writer1 that it is ,impossible to trace the path of a sunbeam through our atmosphere without feeling a desire to know its nature1 by what power it traverses the immensity of space1 and the ,various modifications it undergoes at the surfaces and the interior of terrestrial substances4 ,light is white and colorless1 as long as it does not come in contact with matter4 ,when in apposition with anybody it suffers variable degrees of decomposition1 resulting in color1 as1 by reflection1 dispersion1 refraction and unequal absorption4 ,to ,sir ,i4 ,newton the world is indebted for proving the compound nature of a ray of white light emitted from the sun4 ,the object of this work is not to engage in an extended theory upon the subject of light1 but to recur only to some points-of more particular interest to the photographic operator4 ,sidenote3 ,,prism1 ,,solar ,,spectrum4 ,the decomposition of a beam of light can be noticed by exposing it to a prism4 ,if1 in a dark room1 a beam of light be admitted through a small hole in a shutter #g it will form a white round spot upon the place where it falls4 ,if a triangular prism of glass be placed on the inside of the dark room1 so that the beam of light falls upon it1 it no longer has the same direction1 nor does it form a round spot1 but an oblong painted image of seven colors--red1 orange1 yellow1 green1 blue1 indigo1 and violet4 ,this is called the solar spectrum1 and will be readily understood by reference to the accompanying diagram1 ,fig4 #a4 ,illustration3 ,fig4 #a4 ,to those who are unacquainted with the theory of light 7and for their benefit this chapter is given71 it may be a matter of wonder how a beam of light can be divided4 ,this can be understood when ,i say1 that white light is a bundle of colored rays united together1 and when so incorporated1 they are colorless2 but in passing through the prism the bond of union is severed1 and the colored rays come out singly and separately1 because each ray has a certain amount of refracting 7bending7 power1 peculiar to itself4 ,these rays always hold the same relation to each other1 as may be seen by comparing every spectrum or rainbow2 there is never any confusion or misplacement4 ,there are various other means of decomposing white light besides the prism1 of which one of the principal and most interesting to the photographer1 is by reflection from colored bodies4 ,if a beam of white light falls upon a white surface1 it is reflected without change2 but if it falls upon a red surface1 only the red ray is reflected3 so also with yellow and other colors2 the ray which is reflected corresponds with the color of the object4 ,it is this reflected decomposed light which presents the beautifully colored image we see upon the ground glass in our cameras4 ,sidenote3 ,,light1 ,,heat1 ,,and ,,actinism4 ,a sunbeam may be capable of three divisions--light1 heat1 and actinism2 the last causes all the chemical changes1 and is the acting power upon surfaces prepared to receive the photographic image4 ,the accompanying illustration1 ,fig4 #b1 will readily bring to the minds of the reader the relation of these one to another1 and their intensities in the different parts of a decomposed sunbeam4 ,illustration3 ,fig4 #b4 ,the various points of the solar spectrum are represented in the order in which they occur between ,a and ,b1 this exhibits the limits of the ,newtonian spectrum1 corresponding with ,fig4 #a4 ,sir ,john ,herschel and ,seebeck have shown that there exists1 beyond the violet1 a faint violet light1 or rather a lavender1 to b1 which gradually becomes colorless2 similarly1 red light exists beyond the assigned limits of the red ray to a4 ,the greatest amount of actinic power is shown at ,e opposite the violet2 hence this color exerts the greatest amount of influence in the formation of the photographic image4 ,sidenote3 ,,coloring ,,walls ,,blue4 7,blue paper and blue color have been somewhat extensively used by our operators in their operating rooms and skylights1 in order to facilitate the operation in the camera4 ,i fancy1 however1 that this plan cannot be productive of as much good as thought by some1 from the fact1 that the light falling upon the subject1 and then reflected into the camera1 is1 coming through colorless glass1 not affected by such rays as may be reflected from the walls of the operating room2 and even if it were so1 ,i conceive that it would be injurious1 by destroying the harmony of ,shadows which might otherwise occur47 ,the greatest amount of white light is at ,c2 the yellow contains less of the chemical power than any ,other portion of the solar ,spectrum4 ,it has been found that the most intense heat is at the ,extreme ,red1 b4 ,artificial lights differ in their color2 the white light of turning charcoal1 which is the principal light from candles1 oil and gas1 contains three fays--red1 yellow and blue4 ,the dazzling light emitted from lime intensely heated1 known as the ,drummond light1 gives the color of the prism almost as bright as the solar spectrum4 ,sidenote3 ,,light1 ,,heat1 ,,and ,,chemical ,,power4 ,if we expose a prepared collodionized plate or sensitive paper to the solar spectrum1 it will be observed that the luminous power 7the yellow7 occupies but a small space compared with the influence of heat and chemical power4 ,r4 ,hunt1 in his ,researches on ,light1 has presented the following remarks upon the accompanying illustration3-- ,illustration3 ,fig4 #c4 ,if the linear measure1 or the diameter of a circle which shall include the luminous rays1 is #be1 that of the calorific spectrum will be #dbaj1 and of the chemical spectrum #eeaj4 ,such a series of circles may well be used to represent a beam from the sun1 which may be regarded as an atom of ,light surrounded with an invisible atmosphere of ,heat1 and another still more extended1 which possesses the remarkable property of producing chemical and molecular change4 ,sidenote3 ,,refraction4 ,a ray of light1 in passing obliquely through any medium of uniform density1 does not change its course2 but if it should pass into a denser body1 it would turn from a straight line1 pursue a less oblique direction1 and in a line nearer to a perpendicular to the surface of that body4 ,water exerts a stronger refracting power than air2 and if a ray of light fall upon a body of this fluid its course is changed1 as may be seen by reference to ,fig4 #d4 ,it is observed that it proceeds in a less oblique direction 7towards the dotted line71 and1 on passing on through1 leaves the liquid1 proceeding in a line parallel to that which it entered4 ,it should be observed1 that at the surface of bodies the refractive power is exerted1 and that the light proceeds in a straight line until leaving the body4 ,the refraction is more or less1 and in all cases in proportion as the rays fall more or less obliquely on the refracting surface4 ,it is this law of optics which has given rise to the lenses in our camera tubes1 by which means we are enabled to secure a well-delineated representation of any object we choose to picture4 ,illustration3 ,fig4 #d4 ,when a ray of light passes from one medium to another1 and through that into the first again1 if the two refractions be equal1 and in opposite directions1 no sensible effect will be produced4 ,sidenote3 ,,refraction1 ,,lenses1 ,,focus4 ,the reader may readily comprehend the phenomena of refraction1 by means of light passing through lenses of different curves1 by reference to the following diagrams3-- ,illustration3 ,fig4 #e4 ,fig #f4 ,fig4 #g4 ,fig4 #e representing a double-convex lens1 ,fig4 #f a double-concave1 and ,fig4 #g a concavo-convex or meniscus4 ,by these it is seen that a double-convex lens tends to condense the rays of light to a focus1 a double-concave to scatter them1 and a concavo-convex combines both powers4 ,sidenote3 ,,enlarging ,,or ,,reducing ,,in ,,copying4 ,illustration3 ,fig4 #h4 ,illustration3 ,fig4 #i4 ,if parallel rays of light fall upon a double-convex lens1 ,d ,d1 ,fig4 #h1 they will be refracted 7excepting such as pass directly through the centre7 to a point termed the principal focus4 ,the lines ,a ,b ,c represent parallel rays which pass through the lens ,d ,d1 and meet at ,f2 this point being the principal focus1 its distance from the lens is called the focal length4 ,those rays of light which are traversing a parallel course1 when they enter the lens are brought to a focus nearer the lens than others4 ,hence the difficulty the operator sometimes experiences by not being able to obtain a focus1 when he wishes to secure a picture of some very distant objects2 he does not get his ground glass near enough to the lenses4 ,again1 the rays from an object near by may be termed diverging rays4 ,this will be better comprehended by reference to ,fig4 #i1 where it will be seen that the dotted lines1 representing parallel rays meet nearer the lenses than those from the point ,a4 ,the closer the object is to the lenses1 the greater will be the divergence4 ,this rule is applicable to copying1 ,did we wish to copy a #a_/f size daguerreotype on a #a_/af size plate1 we would place it in such a position to the lenses at ,a1 that the focus would be at ,f1 where the image would be represented at about the proper size4 ,now1 if we should wish to copy the #a_/f size picture1 and produce another of exactly the same dimensions1 we have only to bring it nearer to the lenses1 so that the lens ,d ,e shall be equi-distant from the picture and the focus1 i4 e4 from ,a to ,b4 ,the reason of this is1 that the distance of the picture from the lens1 in the last copy1 is less than the other1 and the divergence has increased1 throwing the focus further from the lens4 ,these remarks have been introduced here as being important for those who may not understand the principles of enlarging or reducing pictures in copying4 ,sidenote3 ,,lenses4 ,i would remark that the points ,f and ,a1 in ,fig4 #i1 are termed conjugate foci4 ,if we hold a double-convex lens opposite any object1 we find that an inverted image of that object will be formed on a paper held behind it4 ,to illustrate this more clearly1 ,i will refer to the following wood-cut3-- ,illustration3 ,fig4 #aj4 ,if ,a ,b ,c is an object placed before a convex lens1 ,l ,l1 every point of it will send forth rays in all directions2 but1 for the sake of simplicity1 suppose only three points to give out rays1 one at the top1 one at the middle1 and one at the bottom2 the whole of the rays then that proceed from the point ,a1 and fall on the lens ,l ,l1 will be refracted and form an image somewhere on the line ,a ,g ,e1 which is drawn direct through the centre of the lens2 consequently the focus ,e1 produced by the convergence of the rays proceeding from ,a1 must form an image of ,a1 only in a different relative position2 the middle point of ,c1 being in a direct line with the axis of the lens1 will have its image formed on the axis ,f1 and the rays proceeding from the point ,b will form an image at ,d2 so that by imagining luminous objects to be made up of an infinite number of radiating points1 and the rays from each individual point1 although falling on the whole surface of the lens1 to converge again and form a focus or representation of that point from which the rays first emerged1 it will be very easy to comprehend how images are formed1 and the cause of those images being reversed4 ,it must also be evident1 that in the two triangles ,a ,g ,b and ,d ,g ,e1 that ,e ,d1 the length of the image1 must be to ,a ,b1 the length of the object1 as ,g ,d1 the distance of the image1 is to ,g ,b1 the distance of the object from the lens4 ,sidenote3 ,,spherical ,,aberration4 ,it will be observed1 that in the last cut the image produced by the lens is curved4 ,now1 it would be impossible to produce a well-defined image from the centre to the edge upon a plain surface2 the outer edges would be misty1 indistinct1 or crayon-like4 ,the centre of the image might be represented clear and sharp on the ground glass1 yet this would be far from the case in regard to the outer portions4 ,this is called spherical aberration1 and to it is due the want of distinctness which is frequently noticed around the edges of pictures taken in the camera4 ,to secure a camera with a flat1 sharp field1 should be the object of every ,operator2 and1 in a measure1 this constitutes the great difference in cameras manufactured in this country4 ,spherical aberration is overcome by proper care in the formation of the lens3--,it can be shown upon mathematical data that a lens similar to that given in the following diagram--one surface of which is a section of an ellipse1 and the other of a circle struck from the furthest of the two foci of that ellipse--produces no aberration4 ,at the earliest period of the employment of the camera obscura1 a double-convex lens was used to produce the image2 but this form was soon abandoned1 on account of the spherical aberration so caused4 ,lenses for the photographic camera are now always ground of a concavo-convex form1 or meniscus1 which corresponds more nearly to the accompanying diagram4 ,illustration3 ,fig4 #aa4 ,sidenote3 ,,chromatic ,,aberration4 ,chromatic ,aberration is another difficulty that opticians have to contend with in the manufacturing of lenses4 ,it will be remembered1 that in a former page 7#ad7 a beam of light is decomposed by passing through a glass prism giving seven distinct colors--red1 orange1 yellow1 green1 blue1 indigo and violet4 ,now1 as has been said before1 the dissimilar rays having an unequal degree of refrangibility1 it will be impossible to obtain a focus by the light passing through a double-convex lens without its being fringed with color4 ,its effect will be readily understood by reference to the accompanying cut4 ,illustration3 ,fig4 #ab4 ,if ,l ,l be a double convex-lens1 and ,r ,r ,r parallel rays of white light1 composed of the seven colored rays1 each having a different index of refraction1 they cannot be refracted to one and the same point2 the red rays1 being the least refrangible1 will be bent to r1 and the violet rays1 being the most refrangible1 to v3 the distance v r constitutes the chromatic aberration1 and the circle1 of which the diameter is a l1 the place or point of mean refraction1 and is called the circle of least aberration4 ,if the rays of the sun are refracted by means of a lens1 and the image received on a screen placed between ,c and o1 so as to cut the cone ,l a l ,l1 a luminous circle will be formed on the paper1 only surrounded by a red border1 because it is produced by a section of the cone ,l a l ,l1 of which the external rays ,l a ,l l1 are red2 if the screen be moved to the other side of o1 the luminous circle will be bordered with violet1 because it will be a section of the cone ,m a ,m l1 of which the exterior rays are violet4 ,to avoid the influence of spherical aberration1 and to render the phenomena of coloration more evident1 let an opaque disc be placed over the central portion of the lens1 so as to allow the rays only to pass which are at the edge of the glass2 a violet image of the sun will then be seen at v1 red at r1 and1 finally1 images of all the colors of the spectrum in the intermediate space2 consequently1 the general image will not only be confused1 but clothed with prismatic colors4 ,to overcome the difficulty arising from the chromatic aberration1 the optician has only to employ a combination of lenses of opposite focal length1 and cut from glass possessing different refrangible powers1 so that the rays of light passing through the one are strongly refracted1 and in the other are bent asunder again1 reproducing white light4 ,to the photographer one of the most important features1 requiring his particular attention1 is1 that he be provided with a good lens4 ,by the remarks given in the preceding pages1 he will be enabled1 in a measure1 to judge of some of the difficulties to which he is occasionally subjected4 ,we have in this country but two or three individuals who are giving their attention to the manufacture of lenses1 and their construction is such1 that they are quite free from the spherical or chromatic aberration4 ,,chapter ,,ii4 ,,camera--,,arrangement ,,of ,,lenses--,,camera ,,tubes--,,camera-,,boxes1 ,,bellows1 ,,and ,,copying--,,camera ,,stands--,,head ,,rests--,,cleaning ,,vice--,,nitrate ,,bath--,,leveling ,,stands--,,printing ,,frames--,,collodion ,,vials4 ,babtista ,porta1 when he saw for the first time1 on the walls of his dark chamber1 the images of external nature1 pictured by a sunbeam which found its way through only a small hole1 little thought of the importance which would be attached to the instrument he was1 from this cause1 led to invent4 ,the camera obscura of this ,italian philosopher remained as a mere scientific toy for years1 and it was not until ,daguerre's discovery that its true value was estimated4 ,it now plays a very important part in giving employment to at least ten thousand persons in this country alone4 ,it is of the utmost importance1 in selecting a set of apparatus1 to secure a good camera2 for without such no one can obtain fine pictures4 ,in testing it1 see that it gives the pupil of the eye and lineaments of the features sharp and distinct2 and that the whole image on the ground glass has a fine pearly hue4 ,look also to the field1 and observe that the focus is good at the centre and extreme edges of the ground glass1 at the same time4 ,a poor camera generally gives a misty image1 with the lights and shades apparently running together4 ,the best ,american cameras are fully equal to those imported1 while they cost much less2 but there are great numbers sold which are not worth using4 ,sidenote3 ,,camera ,,tubes ,,and ,,lenses4 ,if a lens gives a well defined image on the ground glass1 it should do the same on the plate4 ,many a valuable lens has been condemned for failing in this1 merely in consequence of the plate-holder not being in focus with the ground-glass4 ,in case of deficiency in this1 put a glass into the holder1 lay a rule across the face1 and measure the distance between them very exactly2 measure the ground-glass in the same way1 and make the distance agree perfectly1 by moving the ground-glass either back or forward in the frame1 as the case may be1 so that the surface of the glass plate shall occupy precisely the same position as the face of the ground-glass when in the camera4 ,illustration3 ,fig4 #ac4 ,fig4 #ad4 ,sidenote3 ,,position ,,of ,,lenses ,,in ,,the ,,tube4 ,it is very desirable that the operator should understand the arrangement of the lenses in the tube2 it not unfrequently happens1 that in taking out the glasses to clean them1 he does not return them to their proper places1 and the result is that his camera is spoiled4 ,a couple of illustrations and a few remarks will be sufficient to enable any one to replace the lenses in them properly4 ,fig4 #ac represents the tube for holding the lens1 and ,fig4 #ad shows their arrangement4 ,it will be seen that the two back lenses have a small space between them2 this separation is kept by a small tube or ring of the same circumference as the lens4 ,the two front lenses are nearest together4 ,it will be observed that the two thick lenses are towards each other2 these are made of flint glass containing much oxide of lead4 ,the other two are double convex1 and are made of crown glass4 ,by noting the fact that the two cemented lenses go in the front of the tube1 the glass having the thickest edge goes inside1 and that the thickest lens of the other two goes in first1 from the back of the tube1 it will not be easy for the operator to make a mistake in returning the glasses4 ,i will remark that a diaphragm diminishes both chromatic and spherical aberration1 by cutting off the outside portion of the lens4 ,it lessens the brilliancy of the image1 but improves the distinctness by preventing various rays from interfering with and confusing each other2 it also causes a variety of objects at different distances to be in focus at the same time4 ,illustration3 ,fig4 #ae4 ,sidenote3 ,,camera ,,boxes4 ,the tube containing the lenses is to be mounted on a box 7camera-box7 as in ,fig4 #ae4 ,for this purpose there are several patterns of boxes1 from among which ,i have made two selections of the most approved1 and represent them by cuts1 ,figs4 #af1 #ag1 #ah4 ,illustration3 ,fig4 #af4 ,illustration3 ,fig4 #ag4 ,figs4 #af and #ag represent a bellows-box which is probably more in use than all the other patterns together4 ,they serve both for copying and taking portraits from life4 ,a is the base2 ,b is the back and sliding-box2 ,c1 bellows1 which admits of extension or contraction2 ,d is the opening to receive the carriage ,a1 ,fig4 #ag2 ,e is a thumb screw to hold the sliding-box at any required distance4 ,fig4 #ag represents the plate-holder and ground glass frame4 ,a1 carriage to pass through ,d1 ,fig4 #af2 ,b1 frame for ground-glass1 which may be turned in a horizontal or perpendicular position2 ,c1 a movable plate-holder held in place by means of springs2 ,d1 reducing holder1 with bottom and plate to hold the glass plate3 any size of reducing frame can be put in frame ,c2 ,e ,e1 spring bottom to keep frame ,d in place2 ,f1 slide2 ,g1 thumb-screw1 when the carriage is to be put in or taken out of the box1 ,fig #af2 ,h ,h1 spring bottom to hold ,b in place4 ,bellows-boxes can be obtained which receive the plate-holder from the top1 the same as in the copying-box1 ,figs4 #ae and #ah4 ,the common wood1 or copying-box1 is represented by ,fig4 #ah4 ,illustration3 ,fig #ah4 ,a1 being the main or outside box1 is made of wood veneered with rosewood2 ,b is another box which fits into ,a1 sliding in and out as required4 ,the ground glass and plate-holders fit grooves made in the inside box4 ,in regard to plate-holders or tablets for holding the glass plates1 it need only be said that the camera-boxes are accompanied with a complete set1 so arranged that the light is wholly excluded from the plate while drawing out or pushing in the slide1 for shutting off the light while the holder is out of the box4 ,should any one be desirous of using the same camera1 for taking both glass and daguerreotype pictures1 it will be necessary for him to be provided with two sets of tablets for his box1 one for each process4 ,illustration3 ,fig4 #ai4 ,camera ,stands4 ,sidenote3 ,,camera ,,stands1 ,,arm ,,stands4 ,there are several patterns of these2 almost every dealer has some particular style1 which1 if not for beauty1 for his interest1 suits his purposes best4 ,among the assortment1 ,i will present only two illustrations4 ,the first1 ,fig4 #ai1 represents one which has an advantage over many others2 it is made of cast iron1 and of an ornamental pattern3--,a1 base on castors2 ,b1 fluted hollow column1 which admits the iron tube ,c1 which has on one side a hollow tooth rack to receive a spiral thread on the inner face of wheel ,d2 this wheel1 when turned1 elevates or lowers the tube ,c to any desired height2 ,e1 thumb wheel attached to a screw which sets against tube ,c1 to hold it in position1 ,f1 a pinion by which the camera can be directed2 ,g ,g1 thumb screws to hold the two plates together when in position4 ,it is quite heavy1 stands firm and solid1 and is not liable to be moved by the jar from walking over the floor4 ,for permanently located operators these are the most desirable2 but for those who are moving about from place to place1 and those who wish to take views1 a lighter article would be more convenient1 such as one represented at ,fig4 #bj4 ,this stand is made principally of wood1 and can be readily taken apart1 so as to be packed in an ordinary sized trunk4 ,illustration3 ,fig4 #bj4 ,illustration3 ,fig4 #ba4 ,fig4 #ba represents a small ,jenny ,lind ,stand1 and is a very convenient article for the sitter to lean a hand or arm upon while sitting for a portrait2 ,it is fixed with a rod for raising or lowering the top1 and can be adjusted to any required height4 ,head ,rests4 ,sidenote3 ,,head ,,rests4 ,there are several patterns of head supports1 or1 as they are commonly called1 head rests1 in use by the profession4 ,i give two illustrations 7,figs4 #bb and #bc74 ,the first is an independent iron rest1 known as the ,jenny ,lind ,rest2 and the other is for fastening to the back of a chair1 as seen in the cut4 ,for general use1 ,i would recommend the iron independent rest as far more advisable than any other4 ,illustration3 ,fig4 #bb4 ,illustration3 ,fig4 #bc4 ,vices for ,holding ,glass4 ,sidenote3 ,,plate-,,holders1 ,,bath1 ,,dipping ,,rods4 ,the article used for holding the glass1 during the process of cleaning1 is called a vice2 and1 of the numerous styles recently introduced1 ,i find none that ,i would prefer to the old one known in market as ,peck's ,vice2 it is simple and easy in operation1 and at the same time is effectual4 ,fig4 #bd represents this vice1 which is to be firmly secured to a bench2 the small piece of wood attached to the bottom is of no use4 ,a ,a are the grooved for receiving the daguerreotype plate-block2 but as they are too deep for the glass1 ,i pin on a small strip of wood1 so that the upper edge of the glass will be a little above the projection of the vice4 ,illustration3 ,fig4 #bd4 ,illustration3 ,fig4 #be4 ,illustration3 ,fig4 #bf4 ,illustration3 ,fig4 #bg4 ,nitrate ,baths and ,dipping ,rods4 ,the accompanying illustration1 ,fig4 #be1 a1 represents a bath for holding the nitrate of silver solution4 ,this shape is of my own suggestion1 and the best adapted to the wants of the photographer4 ,it will be seen that the front side is rounding1 with a curve extending from side to side4 ,by this shape1 the face of the glass is protected from coming in contact with the side of the bath--both edges of it turning so as to prevent injury4 ,there is a small projection on the top1 at the opposite side of the oval2 this is to allow the solution to flow over and wash off any dust that may have gathered upon the surface of the solution4 ,this wash runs out of a small tube1 as is shown in the cut4 ,any convenient vessel can be placed under it to receive the liquid4 ,this can be filtered and returned as often as required4 ,i am not in the practice of filling my baths full of solution1 but always keep them filtered and clean2 hence saving an excess of solution4 b represents a little support1 which is secured at its base ,upon the shelf1 to hold the bath in a slightly inclined position1 which is preferable to having it stand perpendicularly4 ,illustration3 ,fig4 #bh4 ,illustration3 ,fig4 #bi4 ,illustration3 ,fig4 #cj4 ,leveling ,stands4 ,sidenote3 ,,leveling ,,stands4 ,persons oftentimes require a rest or place to put their glass during development or washing the picture4 ,either of the stands represented by the annexed cut will answer the purpose4 ,fig4 #cj is known to the daguerreotype operator as a gilding stand1 and is the one best adapted to the wants of operators on glass4 ,it may be so arranged as to give the surface of the glass a water-level2 ,d ,d are thumb-screws1 by means of which1 when properly regulated1 the frame ,g may hold glass perfectly level and a large quantity of solution may be poured over the surface4 ,printing ,frames4 ,sidenote3 ,,printing ,,frames4 ,there are numerous methods and apparatus used for holding the negative and the paper during exposure to the light4 ,the following illustrations represent a convenient and economical frame for this purpose4 ,illustration3 ,fig4 #ca4 ,illustration3 ,fig4 #cb4 ,fig4 #ca represents the front of the frame4 ,the negative glass is held upon it by springs attached by screws to the bottom half of the frame1 ,a1 so that they can be turned on or off1 to suit the different sizes of glass4 ,on the other end of the spring are wooden buttons1 which are placed on the edges of the glass negative1 holding it in its place1 and pressing it firmly against the paper which is placed under it4 ,this frame is made of two pieces of inch board1 which are connected by hinges1 falling over as seen in ,fig4 #cb1 ,b being the half that is movable4 ,this movable half is secured in position by means of a wooden button1 attached to ,a on the back and under ,b1 as seen in ,fig4 #cb4 ,the separate pieces1 ,a and ,b1 are bevelled where they connect1 as seen by ,fig4 #ca4 ,d 7in ,fig4 #cb7 is one of the springs1 which can be seen in ,fig4 #ca4 ,the entire bed or face of the frame1 ,a and ,b1 should be covered with a thick piece of satinet cloth1 which may be pasted to the lower half1 ,a1 and extended over the entire surface of ,a and ,b4 ,this forms a pad for the paper4 ,this printing frame can be easily made by any cabinet-maker or carpenter4 ,the springs may be of sheet iron or brass--either will be found sufficiently stiff for the purpose4 ,every operator should be provided with from four to ten frames3 the saving of time will be found to amply repay the expenditure necessary for a good supply4 ,illustration3 ,fig4 #cc4 ,another article called a pressure frame1 is represented in the accompanying figure4 ,this is more expensive than the first1 and is by some considered preferable4 ,another cheap1 convenient and equally good arrangement for holding the negative and paper1 is to take three glasses--say one a full size1 being the one having the negative upon it2 and then take two glasses1 each just half the size of the negative1 and have a piece of very thick heavy cloth cut the size of the negative glass1 which can be put between it and the two half glasses1 and then they can be held together by means of the common spring clothes pin4 ,the advantage of the two glasses at the back is1 that one can be entirely removed while the picture is being examined1 and afterwards returned without1 in the least1 moving the impression4 ,collodion ,vial4--,color-,boxes4 ,sidenote3 ,,collodion ,,vials4 ,,color-,,boxes4 ,this shaped vial is made expressly for collodion1 to which purpose it is admirably adapted4 ,it has a wide mouth1 and is so constructed that the liquid flows clear and free4 ,it is deep1 and with a heavy protruding base1 to prevent its falling4 ,there are two sizes made at present1 one to contain #b-a_/b ounces--the other1 #a-a_/b ounce4 ,i generally use the smaller ones1 but always keep on hand1 and would not be without1 a few of the larger size4 ,illustration3 ,fig4 #cd4 ,illustration3 ,fig4 #ce4 ,fig4 #ce represents a color-box4 ,these can be had of any dealer1 completely fitted1 with color and brushes for use4 ,,chemistry4 ,,practical ,,hints ,,on ,,photographic ,,chemistry4 ,,chapter ,,iii4 ,,soluble ,,cotton--,,manipulation--,,plain ,,collodion--,,bromo-,,iodized ,,collodion ,,for ,,positives--,,ditto ,,for ,,negatives--,,solution ,,of ,,bromide ,,and ,,iodide ,,of ,,potassium ,,and ,,silver--,,double ,,iodide ,,of ,,potassium ,,and ,,silver--,,developing ,,solution--,,fixing ,,the ,,solution--,,brightening ,,and ,,finishing ,,the ,,image--,,photographic ,,chemicals4 ,the chemistry of ,photography requires the attention1 in a greater or less degree1 of every practitioner4 ,it is of the utmost importance1 that those who wish to meet with success in the various processes given1 should not only be provided with a good selection of chemicals1 but also understand the nature of the agent employed4 ,to give a perfectly complete and full list of every agent used would require more time and space than can be given in this work4 ,i shall confine myself to some of the most important1 and to such articles as are of the greatest interest to the practitioner4 ,soluble ,cotton4 ,i have1 in my practice and trade1 adopted the term soluble cotton as the one most appropriate1 making a desirable distinction from the article sold as gun cotton1 they being of a somewhat different nature--gun cotton being the most explosive and least soluble1 while the other preparation is more soluble and less explosive4 ,there are two methods employed in the preparation of soluble cotton2 one being by the use of nitric and sulphuric acids1 and the other with sulphuric acid and nitrate of potash4 ,the last of these ,i would recommend as being the most convenient for those who require only a small quantity of cotton4 ,persons experimenting in the preparation of this article should exercise much care and judgment4 ,a good cotton is not the result of hap-hazard operation4 ,the operator should be acquainted1 as nearly as possible1 with the quality of the chemicals employed1 and the proper mode of manipulation4 ,articles necessary4--,one quart ,wedgewood mortar and pestle1 or evaporating dish2 one glass rod2 one pane of glass1 large enough to cover the mortar or dish2 one ordinary-sized pail two-thirds full of pure rain or distilled water1 and at least ten times that quantity of water at hand2 twelve ounces 7by weight1 avoirdupois7 of nitrate of potash 7,dupont's refined1 pulverized72 twelve ounces 7by measure7 of commercial sulphuric acid2 and three hundred and forty grains of clean1 pure cotton wool4 ,remarks4--,it is advisable that the mortar or dish be deep and narrow1 as the mixture can be better formed in a vessel of this shape4 ,if not convenient to procure a mortar1 a common earthen bowl will answer2 glass is objectionable1 as the heat generated in the combination of the acid and nitre is liable to crack it4 ,a new pail should not be used1 especially if it is painted1 as the acids attack the paint1 and injure the cotton4 ,i prefer one that has been used for some time1 and has been frequently cleaned4 ,a common earthen wash-bowl1 or any large glass dish1 will answer in place of the pail4 ,metal pails or vessels should not be used4 ,nitrate of ,potash 7saltpetre7 should be dry and finely-powdered4 ,i use none other than ,dupont's refined2 this is very nearly1 if not absolutely1 chemically pure4 ,the commercial ,sulphuric ,acid 7oil of vitriol7 of ,america is of great uniformity of strength1 as sold by druggists generally4 ,i use a test-bulb graduated to the proper density1 and have been very successful in my experiments4 ,in some twenty different samples of acid1 used in different cities in the ,united ,states1 ,i found only one that produced a poor cotton1 and this might have been influenced by the moisture of the atmosphere1 it being a very rainy day when ,i used it4 ,during my recent and somewhat extensive practice1 ,i have thought that the fine long fibres of cotton wool do not make so desirable a soluble cotton as that which is heavy or common4 ,four or five very careful experiments upon this point1 have had the effect to produce in me a strong belief that my ideas are entitled to some consideration4 ,i should not select the finest cotton for making soluble cotton1 but now invariably take that which is thick or coarse4 ,the result of my experience is 7other things being equal71 that cotton prepared in fine dry weather has a greater degree of solubility than when prepared in a moist atmosphere3 hence ,i would recommend the experimenter to choose fine1 clear weather for preparing it4 ,manipulation4 ,having at hand every article requisite1 proceed as follows3--,put the nitrate of potash into the mortar or dish2 be sure it is dry and well powdered1 and then add the acid2 stir them well with the pestle and glass rod1 so that the lumps will be all 7or nearly so7 out1 and a pasty solution formed4 ,this operation should not occupy more than two minutes' time4 ,then put in the cotton1 about one-quarter of the whole bulk at a time3 it should be well picked apart1 so that it may come immediately in contact with the acids1 and should be kneaded1 with the pestle and glass rod1 into the solution1 and as soon as wetted1 another quarter should be added and wetted as soon as possible2 so continue until all is in3 then knead with the pestle and mortar for at least four minutes1 or until every fibre of the cotton is saturated with the liquid2 then the mortar should be covered over with the pane of glass1 and allowed to stand for fifteen or twenty minutes2 then the entire contents of the mortar should be thrown into the pail two-thirds full of water1 and stirred with the glass rod as rapidly as possible3 if this rapid stirring is omitted1 the cotton will be injured by the action of the acids in combining with the water4 ,the water should be poured off1 and another change put into the pail4 ,after about three changes1 the hands may be used in the farther washing4 ,the hands should be perfectly clean1 and free from all chemicals4 ,the changes of water and washing should be continued until every trace of acid has disappeared1 which can be seen by testing with blue litmus test-paper4 ,after it is thought that the cotton has become free1 the water may be squeezed out of a little lump about the size of a pea1 and then placed between the fold of the test-paper1 and if it reddens the paper1 there is acid present1 and the washing should be continued until there is no change in the paper4 ,when this is done1 the cotton can be put into the folds of a dry towel or cloth 7which has been thoroughly rinsed1 so that no soap be present71 and wrung out as dry as possible1 and then it may be picked apart and put aside1 exposed to a moderate temperature 7say #ajj ,fahr47 to dry1 when it is ready for use4 ,i employ the method 7for convenience1 nothing more7 of displacing the water by the use of alcohol4 ,cutting's patent--see patents4 ,i wring out the water as before1 then place the cotton in strong alcohol1 stir and press it1 and then pour it off2 wring it out again1 then put it in a change of alcohol1 let it soak for about five minutes1 then wring it out as dry as possible1 pick it apart1 and it will dry immediately1 and place it in a close stoppered bottle2 or1 if wanted for use at once1 put it into the dissolving solution immediately4 ,i will here remark that1 since the first edition1 ,i have had occasion to use large quantities of soluble cotton1 and have found that if it be kept in an atmosphere of alcohol and ether1 its solubility is somewhat improved3 that is1 in the case of its not being used immediately after its preparation4 ,this is easily kept1 by dropping a few drops of ether or alcohol into the bottle containing it1 and then sealing close until wanted for use4 ,in the event of the water being displaced by alcohol1 it is not necessary to thoroughly dry it1 but put in a perfectly close bottle to keep4 ,remarks4--,there are a few precautions necessary to be observed in the preparation of soluble cotton4 ,i should select a fine clear day1 if time is no object2 nevertheless ,i have made a good article in a moderately dense atmosphere4 ,sulphuric acid has a powerful affinity for hydrogen1 consequently1 in damp weather1 it is more or less reduced by the moisture in the air4 ,it is advisable to prepare the nitro-sulphuric acid mixture on a roof1 or between two doors or windows1 where there is a good current of air1 in order to prevent the inhalation of white vapors which arise1 and are very poisonous to the lungs4 ,as a preventive1 in case of inhaling these vapors1 ,i apply the fumes of aqua-ammonia4 ,it is best for every one to have six or eight ounces of this always at hand2 it neutralizes all acid that maybe spattered on the clothes1 prevents its destructive powers1 and restores the color4 ,yellow vapors sometimes appear when putting the cotton in contact with the solution3 this arises from its not being wet2 and when they do appear1 the cotton where they are should be quickly put under the liquid and kneaded rapidly1 which will prevent a continuance of these vapors4 ,i have had them appear1 and used the cotton1 and could not observe that any bad effect had been produced4 ,the temperature is worthy the attention of the operator3 if it be low1 as in winter1 and the cotton be left in the nitro-sulphuric mixture for fifteen or twenty minutes1 the whole becomes a thick1 stiff mass1 bedded together1 and has not had proper action1 giving a bad article4 ,a good temperature is about #adj ,fahr4 for the last of the time the cotton is in the mixture4 ,this is not always convenient2 so the operator will be governed by circumstances1 taking his chance of having a good article4 ,in some cases ,i have heated a thick iron plate1 at a moderate temperature1 placing the mortar upon it1 and thus aided in regulating the temperature4 ,this is the most convenient method ,i have employed4 ,it has been thought advisable to publish in full the account of ,edw4 ,ash ,hadow's experiments and investigations upon the subject of soluble cotton4 ,the following is an account of them as it appeared in ,humphrey's ,journal1 vol4 ,,vi4 p4 #ab3-- ,having1 in my earlier experiments on the collodion process of photography1 experienced some difficulty in always producing a collodion of uniform quality with regard to sensitiveness1 tenacity and fluidity1 although making use of the same materials for its preparation1 and this ,i find being the complaint of many others1 it has been my study lately to determine the variations in quality to which the ingredients are liable1 and the effects of these variations on the sensitive film1 and likewise to ascertain whether the excellent qualities of some samples of collodion depend on the materials in ordinary use1 or on some substances accidentally or intentionally added4 ,researches in the preparation of collodion may appear superfluous1 now that it is supplied of the best quality by so many makers2 but as some persons of an independent turn of mind still prefer manufacturing their own1 ,i venture to bring forward the subject with the hope of benefiting them4 ,in this beautiful process so much depends for success on the quality of the collodion1 that when in possession of a good specimen1 it becomes one of the easiest and most simple1 and ought to be the most certain of all the processes yet devised2 for here no material of uncertain composition is introduced1 such as paper1 and thus we have nothing to fear from plaster of ,paris1 alumina1 or specks of iron or copper1 which continually endanger or modify the calotype process2 each ingredient can and ought to be obtained in a state of perfect purity1 and with this precaution the degree of success depends upon the skill of the operator himself4 ,of all the substances used in this process1 the gun-cotton is usually the only one actually prepared by the operator himself2 in this he cannot fail to have observed the great variations in the solubility1 and1 when dissolved1 the transparency and tenacity of the films1 to which it is liable2 the various processes also that are given appear at first sight unaccountably different1 some directing ten minutes1 others a few seconds immersion4 ,in consequence of this ,i have specially examined into the cause of all these variations1 with a view to obtain certainty1 and also have endeavored to discover how far they affect the sensitiveness of the prepared surface4 ,if we take a mixture of the strongest nitric and sulphuric acids and immerse as much cotton as can be wetted1 after some minutes squeeze out the acid as far as possible1 then immerse a second portion of cotton1 and again express the acids for a third portion of cotton1 and so on until the liquid is exhausted1 we shall find1 on comparing the cottons thus treated1 after washing and drying1 that there is a gradual alteration in their properties1 the first being highly and perfectly explosive1 and each succeeding portion less so1 until the portion last immersed will be found hardly explosive1 leaving distinct traces of charcoal or soot when burned4 ,this may not appear surprising at first sight1 as it may be imagined that the latter portions are only a mixture of gun-cotton and common cotton2 this is1 however1 not the case1 for if each quantity be immersed sufficiently long1 it will not contain a fibre of common cotton1 and may yet become charred on burning like unaltered cotton4 ,the most remarkable difference1 however1 is discovered on treating them with ether containing a little alcohol1 when1 contrary to what might have been anticipated1 the first or strongest gun-cotton remains untouched1 while the latter portions dissolve with the utmost ease1 without leaving a trace behind1 which alone is sufficient proof that no unaltered cotton remains4 ,this difference in properties is owing to the gradual weakening of the acid mixture1 in consequence of the nitric acid being removed by the cotton1 with which it becomes intimately combined1 at the same time that the latter gives out a proportionate quantity of water4 ,in consequence of these experiments1 a great many mixtures of these acids were prepared of various strengths1 each being accurately known1 both to determine whether there were more than one kind of soluble gun-cotton1 and1 if there were1 to ascertain exactly the mixture required to produce the most suitable to photographic purposes4 ,by this means1 and by1 what ,i believe has not been pointed out1 varying the temperature1 at least five varieties were obtained2--first1 gun-cotton1 properly so called1 as before stated1 quite insoluble in any mixture of alcohol and sulphuric ether4 ,secondly1 an explosive cotton1 likewise insoluble1 but differing chemically from the first1 obtained by a mixture of certain strength when used cold4 ,if warm1 however1 either from the heat produced spontaneously on mixing the two acids2 or by raising the temperature artificially to about #acj1 the cotton then immersed becomes perfectly soluble1 producing a third variety2 if1 however1 it be thoroughly dried1 it becomes in a great measure insoluble4 ,the fourth is obtained by the use of weaker acids used cold1 and the fifth when the mixture has been warmed to #acj previous to the immersion of the cotton2 in either of the two last cases the product is perfectly soluble1 but there is a remarkable difference between their properties1 for on dissolving #f grains of each in #a ounce of ether1 the cotton treated with warm acids gives a perfectly fluid solution 7which is likewise the case with the third variety produced by acids something stronger71 while that obtained by the use of cold acids makes a mixture as thick as castor-oil4 ,having obtained these more strongly marked varieties1 as well as intermediate kinds1 with all gradations of solubility1 it was necessary1 before ,i could select any particular formula for preparing the cotton1 to compare their photographic properties1 with especial reference to sensitiveness1 opacity of the reduced silver in negatives1 and its color in positives4 ,a certain weight of each being dissolved in a portion of the same mixture of alcohol and ether previously iodized1 the comparison was made1 by taking the same objects with each collodion in succession1 and likewise by pouring two samples on the same plate of glass1 and thus exposing them in the camera together1 side by side2 this last proved to be much the most satisfactory plan1 and was repeated many times for each sample1 taking care to reverse the order in which they were poured on1 that there might be no mistake arising from the difference of time elapsing between the pouring on of the collodion and its immersion in the sensitive bath4 ,by these experiments ,i had confidentially hoped to have solved the question as to the cause of difference in sensitiveness and other photographic properties of collodion2 but in this ,i was disappointed1 for1 after repeated experiments1 ,i believe ,i may safely affirm that they are precisely similar as regards their photographic properties4 ,the same ,i believe may be said of ,swedish paper collodion1 judging from a few comparative experiments ,i have made1 and indeed it is difficult to discover what is the superiority of this material over clean cotton-wool2 the ease of manipulation which some allege is a matter of taste1 but ,i should decidedly prefer the open texture of cotton to that of a substance like filtering paper1 composed of a mass of compacted fibres1 the innermost of which are only reached when the acids have undergone a certain degree of weakening by the water abstracted from the outer fibres2 and when we consider that from cotton alone we have the means of preparing all varieties of collodion1 from the most powerfully contracting and transparent to the weakest and most opaque1 and each if required with equal and perfect certainty1 there appears to be choice enough without resorting to another material1 differing only in being more rare and more difficult to procure4 ,but1 although the photographic properties of these varieties of collodion-wool are so similar1 other circumstances1 such as fluidity1 tenacity1 and transparency1 render its preparation of some importance1 and indicate that the acid mixture should always be used warm2 and it is chiefly in consequence of this very circumstance1 that greater success attends the use of nitrate of potash and sulphuric acid than that of mixed acids2 for the former when mixed1 produce the required temperature1 and must be used while warm1 since on cooling the mixture becomes solid1 whereas acids when mixed do not usually produce so high a temperature1 and being fluid can be used at any subsequent period2 another obstacle to their use is the great uncertainty of the strength of the nitric acid found in the shops1 requiring a variation in the amount of sulphuric acid to be added1 which would have to be determined by calculation or many troublesome trials4 ,when a proper mixture is obtained1 the time of immersion is of no importance1 provided it be not too short1 and the temperature be maintained at about #abj or #acj2 ten minutes is generally sufficient2 7though ten hours would not render the cotton less soluble1 as is sometimes asserted47 ,in using the mixed acids1 the limits are the nitric acid being too strong1 in which case the product is insoluble1 or too weak1 when the cotton becomes immediately matted or even dissolved1 if the mixture is warm4 ,i have availed myself of these facts in order to produce collodion-wool by the use of acids1 without the trouble of calculating the proper mixture according to their strength4 ,five parts by measure of sulphuric acid1 and four of nitric acid of specific gravity not lower than #ad1 are mixed in an earthenware or thin glass vessel capable of standing heat2 small portions of water are added gradually 7by half drachms at a time1 supposing two ounces to have been mixed17 testing after each addition by immersion of a small portion of cotton2 the addition of water is continued until a fresh piece of cotton is found to contract and dissolve on immersing2 when this takes place1 add half the quantity of sulphuric acid previously used1 and 7if the temperature does not exceed #acj1 in which case it must be allowed to cool to that point17 immerse as much cotton1 well pulled out1 as can be easily and perfectly soaked2 it is to be left in for ten minutes1 taking care that the mixture does not become cold1 and then transferred to cold water1 and thoroughly washed2 this is a matter of much importance1 and should be performed at first by changing the water many times1 until it ceases to taste acid1 and then treating it with boiling rain-water until the color of blue litmus remains unchanged2 the freedom from all trace of acid is insured by adding a little ammonia before the last washing4 ,cotton thus prepared should dissolve perfectly and instantaneously in ether containing a little alcohol1 without leaving a fibre behind1 and the film it produces be of the greatest strength and transparency1 being what ,m4 ,gaudin terms 'rich in gun-cotton4' ,the mixture of nitrate of potash and sulphuric acid is defective chiefly from the want of fluidity1 in consequence of which the cotton is less perfectly acted on2 this may be remedied by increasing the amount of sulphuric acid1 at the same time adding a little water2 a mixture of #e parts of dried nitre1 with #aj of sulphuric acid1 by weight1 together with #a of water1 produces a much better collodion wool than the ordinary mixture of #a of nitre with #a-a_/b of sulphuric acid4 ,the nitre is dried before weighing1 in order that its amount1 as well as that of the water contained in the mixture1 may be definite in quantity2 it is then finely powdered1 mixed with the water1 and the sulphuric acid added2 the cotton is immersed while the mixture is hot1 and afterwards washed with greater care even than is required when pure acids are used1 on account of the difficulty of getting rid of all the bisulphate of potash that adheres to the fibres1 which both acts as an acid and likewise causes the collodion to appear opalescent when held up to the light2 whereas the solution should be perfectly transparent4 ,plain ,collodion4 ,sidenote3 ,,plain ,,collodion4 ,to dissolve the soluble cotton 7pyroxyline71 and form plain collodion1 proceed as follows3 ,take of ,sulphuric ether 7concentrated71 #aj ounces ,alcohol1 from #ij to #ie per cent41 #f ,soluble cotton enough to give the solution a consistency such as will allow it to flow evenly over the surface of the glass1 and impart to it quite a thick and transparent coating4 ,if the coating is opaque1 the cotton has not been properly prepared1 the acid mixture has been too weak4 ,remarks4--,it is desirable for every operator to use chemicals of uniform strength1 and the better method to adopt is to employ those purchased from some one respectable manufactory1 and not take those furnished by irresponsible and unconscientious parties4 ,at least one-half of the failures experienced by beginners is from want of good chemicals4 ,it is not economy to purchase a cheap article4 ,alcohol is an article that can be procured in almost any small village in the ,united ,states1 and is in general fit for collodion purposes4 ,i have used #hh per cent1 in the above proportions1 also the intermediate varieties to #ih per cent41 and have been quite successful2 but feel convinced that the ordinary #ih1 as marked 7which usually stands by actual test #ie to #ig per cent471 is preferable1 except in cases where water is employed in dissolving the iodizing salts1 when ,i would use fully #ih per cent4 ,before concluding the subject on plain collodion1 ,i will introduce the account given by ,mr4 ,e4 ,a4 ,hadow of his interesting and valuable experiments1 as published in ,humphrey's ,journal1 ,vol4 ,,vi1 page #ah4 ,having obtained good collodion-wool1 the next point of inquiry was with regard to the solvent2 to ascertain whether the addition of alcohol beyond what is necessary to cause the solution of the gun-cotton in ether1 were beneficial or otherwise4 ,for this purpose ether and alcohol were prepared perfectly pure1 and mixtures were made of #a of alcohol to #g of ether1 #b to #f1 #c to #e1 #d to #d and #e to #c4 ,in one ounce of each were dissolved #f grains of gun-cotton and #d grains of iodide of ammonium 7iodide of potassium could not be employed1 since it requires a certain amount both of water and alcohol to keep it in solution72 they were then compared1 using a #ce-;grain solution of nitrate of silver1 both by pouring on separate glasses1 and likewise by covering two halves of a plate with two samples1 as in examining the gun cottons1 thus placing them under the same circumstances during the same time2 in this way the effect of adding alcohol was very clearly perceived1 since the difference between the collodions was much greater than could have been anticipated4 ,the first mixture containing only #a_/hth of alcohol was quite unfit for photographic purposes1 from its being almost impossible1 even with the most rapid immersion1 to obtain a film of uniform sensitiveness and opacity throughout1 the surface generally exhibiting nearly transparent bands1 having an iridescent appearance by reflected light4 ,the second mixture with #a_/dth of the alcohol is liable to great uncertainty1 for if there be any delay in pouring off the collodion the same appearances are seen as in the first1 and like it the surface is very insensitive to light1 while if the plate be rapidly plunged in the bath1 the collodion film becomes much more opaque than before1 and is then very sensitive4 ,the third proportion of #c of alcohol to #e of ether is decidedly the best1 giving without the least difficulty a beautifully uniform and highly sensitive film1 at the same time perfectly tough and easily removable from the glass if required4 ,a further addition of alcohol1 as in the two last collodions1 was not attended with any corresponding advantage or increase of sensitiveness2 on the contrary1 the large proportion of alcohol rendered them less fluid1 though with a smaller quantity of gun cotton they would produce very good collodions1 capable of giving fine films3 the cause of the weakness of the film1 observed on adding much of the ordinary alcohol1 is the large amount of water it usually contains4 ,this surprising improvement1 caused by the addition of a certain quantity of alcohol1 is referable to causes partly chemical1 partly mechanical1 for1 on examining the films1 it will be found in the first1 and occasionally in the second collodion1 that the iodide of silver is formed on the surface1 and can be removed entirely by friction without destroying the transparent collodion film below1 while in those collodions that contain more than one-fourth of alcohol1 the iodide of silver is wholly in the substance1 and in this state possesses the utmost sensitiveness4 ,this difference of condition is owing to the very sparing solubility of ether in water1 which in the first case prevents the entrance of the nitrate of silver into the film1 consequently the iodide and silver solutions meet on the surface2 but on addition of alcohol1 its solubility enables the two to interchange places1 and thus the iodide of silver is precipitated throughout the substance in a state of the utmost division4 ,this difference is clearly seen under the microscope1 the precipitate being clotted in the one case1 while in the other the particles are hardly discoverable from their fineness4 ,the presence of a little water considerably modifies these results1 since it in some degree supplies the place of alcohol1 and is so far useful2 but in other respects it is injurious1 for1 accumulating in quantity1 if the collodion is often used1 it makes the film weak and gelatinous1 and what is worse1 full of minute cracks on drying1 which is never the case when pure ether and alcohol are used4 ,since the ether of the shops almost always contains alcohol1 and frequently water1 it is important to ascertain their amount before employing it for the preparation of collodion2 the quantity of alcohol may be easily ascertained by agitating the ether in a graduated measure glass 7a minim glass does very well7 with half its bulk of a saturated solution of chloride of calcium2 this should be poured in first1 its height noted1 and the ether then poured on its surface1 the thumb then placed on the top1 and the two agitated together2 when separated1 the increase of bulk acquired by the chloride of calcium indicates the quantity of alcohol present1 and for this allowance should be made1 in the addition of alcohol afterwards to the collodion4 ,water is readily detected1 either in ether or alcohol by allowing a drop to fall into spirits of turpentine1 with which they ought to mix without turbidity2 this is immediately produced if they contain water3 for detecting water in alcohol1 benzole is a more delicate re-agent than spirits of turpentine 7,chemist1 xxix1 #bjc74 ,it is also necessary that ether should be free from a remarkable property it acquires by long keeping1 of decomposing iodides and setting free iodine1 which thus gives the collodion a brown color2 the same property may be developed in any ether1 as ,schonbein discovered by introducing a red hot wire into the vapor in the upper portion of a bottle containing a little ether and water2 if it be then shaken up and a solution of iodide poured in1 the whole rapidly becomes brown2 this reaction is very remarkable and difficult to explain for even a mixture of the ether and nitric acid fails to produce a color immediately4 ,ether thus affected can only be deprived of this property by rectification with caustic potash4 ,bromo-,iodized ,collodion for ,positives4--,no4 #a4 ,sidenote3 ,,iodized ,,collodion ,,for ,,positives4 ,one very important object in connection with this part of the collodion process is to have chemicals of a good quality1 and always employ those of a fixed standard4 ,plain collodion1 #aj ounces4 ,solution of bromide1 and iodide of potassium and silver1 7page #fa7 #c drachms4 ,iodide of ammonium1 #aj grains4 ,hydro-bromic acid #f drops4 ,double iodide of potassium and silver 7see page #fb7 enough so that when the plate comes from the nitrate of silver bath1 it will have an opaque cream color4 ,remarks4--,in the preparation of this sensitive collodion1 it is necessary to be cautious and not add too much of the iodide of potassium and silver1 for in that case the coating would flake off1 and falling into the silvering solution1 the operator would be obliged to filter it before he could silver his plate with safety as regards spotting it4 ,the method ,i employ is to add the plain collodion1 bromide and iodide of potassium and silver1 iodide of ammonium and hydro-bromic acid1 and then cautiously add the double iodide of potassium and silver from five to ten drops at a time1 trying the collodion from time to time by pouring a little on a narrow strip of glass1 which ,i dip into the silvering solution1 and let it remain for two minutes4 ,if the coating assumes the proper color 7a cream color71 ,i shake the contents of the bottle1 and then stand it aside to settle3 it is better after it has stood for a week or two4 ,this collodion ,i have used after it has been made eight months1 and produced fine and satisfactory results1 and use this nearly altogether in practice4 ,since the first edition of this work has been issued1 ,i have sold over two thousand pounds of this preparation1 and the demand is on the increase4 ,i will append another preparation 7,no4 #b7 which ,i have successfully employed1 and some operators prefer4 ,bromo-,iodized ,collodion for ,positives4--,no4 #b4 ,plain collodion #aj ounces4 ,iodide of potassium #cj grains4 ,bromide of ammonium #bj ,enough of the double iodide of potassium and silver to give the coating a cream color when it comes from the silvering solution4 ,it will take from one to three drachms4 ,or this last may be omitted1 and a few drops of a saturated solution of dry iodine in alcohol may be added4 ,either of these plans have been successful in my practice4 ,remarks4--,the iodide of potassium being insoluble in the collodion1 it should be first dissolved in as little water as possible2 i4 e41 take the quantity1 #cj grains1 put it into a one-ounce graduate1 and with a glass rod stir it1 adding water1 drop by drop1 only until all of the salt is dissolved4 ,then it may be poured into the collodion1 and there will be a white powdery precipitate4 ,the bromide of ammonium will dissolve in the collodion1 and can be put into it4 ,when all of the accelerators are in1 it should be well shaken1 and then allowed to settle and become clear4 ,when wanted1 a sufficient quantity may be poured into a vial 7see ,fig4 #cd7 for use1 and the main or stock bottle should not be disturbed oftener than necessary4 ,this last collodion is not as durable as the first1 but is less trouble to prepare4 ,bromo-,iodized ,collodion for ,negatives4 ,sidenote3 ,,iodized ,,collodion ,,for ,,negatives ,plain collodion #h ounces4 ,iodide of potassium 7dissolved as per page #fb7 #bd grains4 ,bromide of ammonium #af ,this collodion should be allowed to stand and settle twenty-four hours before it is used3 when wanted1 it should be poured off into a collodion vial4 ,the more free the collodion is from sediment and small particles of dust or undissolved cotton1 the softer and more perfect will be the impression it makes4 ,in case the above proportions of iodide of potassium should not produce a cream-colored coating1 when it comes from the nitrate of silver bath1 more may be added3 for example1 if the coating is of a bluish tint1 ,i would dissolve #f grains of iodide of potassium in water1 as before1 and then try it3 shake well1 and test it by putting a little on a slip of glass1 and dipping it into the silvering solution2 if it coats to a cream-color1 it is right4 ,it should be borne in mind1 that after the addition of iodide of potassium here recommended1 the collodion should be allowed to stand until settled1 before undertaking to produce a picture1 although the coating may be previously tested by means of a slip of glass4 ,solution of ,bromide and ,iodide of ,potassium and ,silver4 ,dissolve #acj grains of crystallized nitrate1 of silver in #d ounces of pure water1 in a long #h-ounce vial4 ,then in a clean #a-ounce graduate1 or some other convenient vessel containing half an ounce of water1 dissolve #acj grains bromide of potassium4 ,when this and the nitrate of silver are both dissolved1 pour the solution of bromide of potassium into the vial containing the silver1 and a thick yellow precipitate will fall4 ,this is the bromide of potassium and silver4 ,this should be washed by nearly filling the vial with water2 shake it1 and then let it settle1 which it will readily do1 and then pour on the water1 leaving the yellow mass in the bottom of the vial2 continue this operation of washing for at least ten changes of water2 then1 after draining off the water as close as possible1 put into the vial four ounces of alcohol1 shake it well and let it settle2 then pour off as close as possible4 ,by this means the water is nearly all taken out4 ,pour into the vial three ounces of alcohol2 then in a small mortar finely pulverize one ounce of iodide of potassium1 and the solution1 which was before clear1 will be more or less of a yellow color1 and the bulk of the yellow precipitate will be diminished4 ,i have sometimes completely re-dissolved the yellow precipitate1 but this does not often occur1 except there be more water present than is advisable4 ,it is better to have an excess of bromide of potassium in the solution4 ,this can be seen by its being white1 and remaining undissolved in the bottom of the vial4 ,this solution should be prepared in the evening1 or in a dark room1 and only the light of a lamp or candle employed4 ,double ,iodide of ,potassium and ,silver4 ,this solution is made in the same manner as in the foregoing article1 substituting the iodide of potassium for the bromide--no bromide being used in this preparation4 ,the yellow precipitate in this case will be re-dissolved and taken up in the solution3 it may require more than one ounce of pulverized iodide of potassium to effect this1 but it may be added in excess1 so that the solution shall contain a quantity in powder4 ,developing ,solution4 ,sidenote3 ,,developing ,,solution4 ,protosulphate of iron1 #c ounces4 ,rain or distilled water1 #a quart4 ,put these into a quart bottle1 and shake until the crystals are all dissolved1 and this can be kept for a stock bottle1 and when wanted for use pour into another bottle4 ,of the above solution1 #e ounces4 ,acetic acid 7,no4 #h7 #a ,chemically pure nitric acid #bj drops4 ,shake this mixture well1 and filter through a sponge1 and it is ready for use4 ,i file a mark in this bottle indicating five ounces1 and another for #a ounce3 this will save time in mixing the solution4 ,remarks4--,in my recent tour of the ,united ,states1 ,i found it difficult to obtain a good article of protosulphate of iron1 and in its stead ,i used the common copperas1 such as ,i could find almost in any store4 ,i employ from one-fourth to one-half more than the quantity given above4 ,if it looked a clear green1 and free from a white or brownish powder1 about one-fourth addition3 i4 e41 four ounces1 instead of three1 as given above4 ,if the solution in the stock bottle is not wanted for a week or more1 a few crystals of the protosulphate of iron should be added1 as it decomposes1 and the strength is depreciated4 ,there is quite a difference in the strength of the acetic acid as sold by out country druggists1 and the operator should be sure that he has ,no4 #h1 to which quality the above proportions are adapted4 ,i never have employed the developing solution but once1 but can see no objections to use it for a number of glass plates1 but it should be filtered every time before using4 ,the quantity of nitric acid may be increased1 so long as a proper proportion is preserved with the strength of the bath4 ,the effect of this addition of acid will be to brighten the impression2 but if carried too far1 the reduction 7developing7 will be irregular1 and the harmony of the impression injured4 ,fixing ,solution4 ,sidenote3 ,,fixing ,,solution4 ,water1 #h ounces4 ,cyanide of potassium1 about #a drachms ,remarks4--,i put enough of the cyanide of potassium into the water to make the solution of such strength as to dissolve off the iodide of silver 7coating7 in from twenty to sixty seconds4 ,the operation is quite similar to that of hyposulphate of soda upon the coating of the ,daguerreotype plate4 ,a too concentrated solution is likely to injure the sharpness of the image4 ,brightening and ,finishing the ,image4 ,sidenote3 ,,humphrey',s ,,collodion ,,gilding4 ,the article ,i now employ for finishing off my ,positives is in market1 and known as ,humphrey's ,collodion ,gilding4 ,it is a new preparation1 and exerts a powerful influence upon the image1 having the same brightening effect as chloride of gold on the daguerreotype4 ,there is no article now in market that equals this4 ,i have until quite recently used a varnish for this purpose1 but having something that is of far greater value1 ,i have discarded it4 ,it is one of the most valuable improvements since the application of the ,collodion ,film as a vehicle for producing photographic images4 ,it is a new discovery1 and is being rapidly brought into use by the first ambrotypers and photographers in ,america4 ,it adds at least one-half to the beauty of an ambrotype1 above any method heretofore in use4 ,it is imperishable1 giving a surface almost equal in hardness to the glass itself4 ,it is easy of application2 it gives a brilliant finish2 it is not affected by a moist atmosphere2 it is not affected by pure water2 it is the best article ever used for finishing ambrotypes2 it will preserve glass negatives for all time2 it will preserve the whites in the ambrotype2 it gives a rich lustre to drapery2 it will bear exposure to the hot sun2 it preserves positives and negatives from injury by light4 ,it is an article that1 when once tried1 the operator upon glass 7positive1 negative1 or albumenized plates7 will not do without4 ,the ingredients in the composition of this gilding are neither patented nor published1 but it can be procured from any dealer in photographic chemicals4 ,nitrate of ,silver ,bath4 ,sidenote3 ,,nitrate ,,of ,,silver ,,bath4 ,i here give what ,i consider an improvement on the bath mentioned in the first edition of this work4 ,i first published it in ,humphrey's ,journal1 ,no4 #bc1 ,vol4 ,,vii43 ,the nitrate of silver solution is an important mixture in the chemical department of the ambrotype process1 and requires the especial care of the operator in its preparation4 ,i give the following as one of the most approved for general practice4 ,it is well adapted to the production of positives1 and its action is of great uniformity4 ,pure water #a ounce4 ,nitrate of silver in crystals neutral to acid test #de grains4 ,nitric acid ,c4 ,p4 ,quantity as given below4 ,this proportion is to be observed for any quantity of solution4 ,if ,i were to prepare a bath #dj ounces1 ,i would proceed as follows3 ,water #dj ounces4 ,nitrate of silver #ahjj grains4 ,measure the water1 and put into a two-quart bottle2 then pour out #h oz4 of it in a pint bottle1 and into this put the whole of the nitrate of silver 7#ahjj gr472 shake it well until it is all dissolved4 ,this forms a concentrated solution--into which put the following prepared iodide of silver3-- ,dissolve in a #c or #d oz4 bottle containing #a oz4 water1 #aj gr4 nitrate of silver2 and in another bottle or graduate containing a little water1 dissolve #aj grains of iodide of potassium2 pour this into the #aj grain solution of nitrate of silver1 and a yellow substance 7iodide of silver7 will precipitate2 fill the bottle with water1 and let it settle2 then pour off the water1 leaving the yellow mass behind2 again pour on it clean water1 shake it1 and let it settle as before1 and pour off again2 repeat this for about six changes of water4 ,then it 7the iodide of silver7 is to be put into the bottle containing the #h oz4 water and #ahjj gr4 of nitrate of silver2 shake it well1 and it will nearly or quite all dissolve2 pour this into the two-quart bottle1 and shake well2 it will be of a yellowish white tint1 and should be filtered through asbestos or sponge1 when it will become clear4 ,when clear1 test the solution with blue litmus-paper2 if it turns it red1 it is sufficiently acid2 if it does not change it1 add one or two drops of nitric acid1 chemically pure2 then test it again2 if it does not change it1 add one or two drops more1 or just enough to change the paper to the slightest red4 ,a solution prepared in this proportion will1 like others1 improve by age4 ,an old bath is considered far more valuable than one newly prepared4 ,these remarks may appear to old photographic operators as of no importance1 but they must bear in mind that there are hundreds just adopting this new process of picture taking4 ,this solution will work more satisfactorily than the one ,i formerly used4 ,it will work quicker in the camera1 and is equally durable4 99 99 99 99 99 ,acknowledgment4--,the following pages1 under the head of ,vocabulary of ,photographic ,chemicals1 and treating upon the ,chemicals used in ,photography1 are taken from the third edition of ,hardwich's ,photographic ,chemistry3-- ,vocabulary of ,photographic ,chemicals4 ,sidenote3 ,,vocabulary ,,of ,,photographic ,,chemicals4 ,acetic ,acid4 ,symbol1 ,c#d;,h#c,o#c ,,ho4 ,atomic weight1 #fj4 ,acetic acid is a product of the oxidation of alcohol4 ,spirituous liquids1 when perfectly pure1 are not affected by exposure to air2 but if a portion of yeast1 or nitrogenous organic matter of any kind1 be added1 it soon acts as a ferment1 and causes the spirit to unite with oxygen derived from the atmosphere1 and to become sour from formation of acetic acid or vinegar4 ,acetic acid is also produced on a large scale by heating wood in close vessels2 a substance distils over which is acetic acid contaminated with empyreumatic and tarry matter2 it is termed pyroligneous acid1 and is much used in commerce4 ,the most concentrated acetic acid may be obtained by neutralizing common vinegar with carbonate of soda and crystallizing out the acetate of soda so formed2 this acetate of soda is then distilled with sulphuric acid1 which removes the soda and liberates acetic acid3 the acetic acid being volatile1 distils over1 and may be condensed4 ,properties of ,acetic ,acid4--,the strongest acid contains only a single atom of water2 it is sold under the name of glacial acetic acid1 so called from its property of solidifying at a moderately low temperature4 ,at about #ej the crystals melt1 and form a limpid liquid of pungent odor and a density nearly corresponding to that of water2 the specific gravity of acetic acid1 however1 is no test of its real strength1 which can only be estimated by analysis4 ,the commercial glacial acetic acid is often diluted with water1 which may be suspected if it does not solidify during the cold winter months4 ,sulphurous and hydrochloric acids are also common impurities4 ,they are injurious in photographic processes from their property of precipitating nitrate of silver4 ,to detect them proceed as follows3--dissolve a small crystal of nitrate of silver in a few drops of water1 and add to it about half a drachm of the glacial acid2 the mixture should remain quite clear even when exposed to the light4 ,hydrochloric and sulphurous acids produce a white deposit of chloride or sulphite of silver2 and if aldehyde or volatile tarry matter be present in the acetic acid1 the mixture with nitrate of silver1 although clear at first1 becomes discolored by the action of light4 ,many photographers employ a cheaper form of acetic acid1 sold by druggists as ,beaufoy's acid2,a it should be of the strength of the acetic acid fortiss4 of the ,london ,pharmacopoeia1 containing #cj per cent1 real acid1 and must be tested for sulphuric acid 7see sulphuric acid71 and also by mixing with nitrate of silver4 ,footnote ,a3 ,in this country the practitioner uses the article sold in market as ,acetic ,acid1 ,no4 #h4--,s4 ,d4 ,h4 ,acetate of ,silver4 7,see ,silver1 ,acetate of47 ,albumen4 ,albumen is an organic principle1 found both in the animal and vegetable kingdom4 ,its properties are best studied in the white of egg1 which is a very pure form of albumen4 ,albumen is capable of existing in two states2 in one of which it is soluble1 in the other insoluble in water4 ,the aqueous solution of the soluble variety gives a slightly alkaline reaction to test-paper2 it is somewhat thick and glutinous1 but becomes more fluid on the addition of a small quantity of an alkali1 such as potash or ammonia4 ,soluble albumen may be converted into the insoluble form in the following ways3-- #a4 ,by the application of heat4--,a moderately strong solution of albumen becomes opalescent and coagulates on being heated to about #aej1 but a temperature of #bab is required if the liquid is very dilute4 ,a layer of dried albumen cannot easily be coagulated by the mere application of heat4 #b4 ,by addition of strong acids4--,nitric acid coagulates albumen perfectly without the aid of heat4 ,acetic acid1 however1 acts differently1 appearing to enter into combination with the albumen1 and forming a compound soluble in warm water acidified by acetic acid4 #c4 ,by the action of metallic salts4--,many of the salts of the metals coagulate albumen very completely4 ,nitrate of silver does so2 also the bichloride of mercury4 ,ammoniacal oxide of silver1 however1 does not coagulate albumen4 ,the white precipitate formed on mixing albumen with nitrate of silver is a chemical compound of the animal matter with protoxide of silver4 ,this substance1 which has been termed albuminate of silver1 is soluble in ammonia and hyposulphite of soda2 but after exposure to light1 or heating in a current of hydrogen gas1 it assumes a brick-red color1 being probably reduced to the condition of a salt of the suboxide of silver4 ,it is then almost insoluble in ammonia1 but enough dissolves to tinge the liquid wine-red4 ,the author is of opinion that the red coloration of solution of nitrate of silver employed in sensitizing the albumenized photographic paper is produced by the same compound1 although often referred to the presence of sulphuret of silver4 ,albumen also combines with lime and baryta2 and chloride of barium has been recommended in positive printing upon albumenized paper1 probably from this cause4 ,chemical composition of albumen4--,albumen belongs to the nitrogenous class of organic substances4 ,it also contains small quantities of sulphur and phosphorus4 ,alcohol4 ,symbol1 ,c#d;,h#f,o#b4 ,atomic weight1 #df4 ,alcohol is obtained by the careful distillation of any spirituous or fermented liquor4 ,if wine or beer be placed in a retort1 and heat applied1 the alcohol1 being more volatile than water1 rises first1 and is condensed in an appropriate receiver2 a portion of the vapor of water1 however1 passes over with the alcohol1 and dilutes it to a certain extent1 forming what is termed spirits of wine4 ,much of this water may be removed by redistillation from carbonate of potash2 but in order to render the alcohol thoroughly anhydrous1 it is necessary to employ quick lime which possesses a still greater attraction for water4 ,an equal weight of this powdered lime is mixed with strong alcohol of #hbc1 and the two are distilled together4 ,properties of ,alcohol4--,pure anhydrous alcohol is a limpid liquid1 of an agreeable odor and pungent taste2 sp4 gr4 at #fj1 #gid4 ,it absorbs vapor of water1 and becomes diluted by exposure to damp air2 boils at #agc ,fahr4 ,it has never been frozen4 ,alcohol distilled from carbonate of potash has a specific gravity of #hae to #hbc1 and contains #ij to #ic per cent1 of real spirit4 ,the specific gravity of ordinary rectified spirits of wine is usually about #hdj1 and it contains #hj to #hc per cent1 of absolute alcohol4 ,ammonia4 ,symbol1 ,,nh#c or ,,nh#d,o4 ,atomic weight1 #ag4 ,the liquid known by this name is an aqueous solution of the volatile gas ammonia4 ,ammoniacal gas contains #a atom of nitrogen combined with three of hydrogen3 these two elementary bodies exhibit no affinity for each other1 but they can be made to unite under certain circumstances1 and the result is ammonia4 ,properties of ,ammonia4--,ammoniacal gas is soluble in water to a large extent2 the solution possessing those properties which are termed alkaline4 ,ammonia1 however1 differs from the other alkalies in one important particular--it is volatile3 hence the original color of turmeric paper affected by ammonia is restored on the application of heat4 ,solution of ammonia absorbs carbonic acid rapidly from the air1 and is converted into carbonate of ammonia2 it should therefore be preserved in stoppered bottles4 ,besides carbonate1 commercial ammonia often contains chloride of ammonium1 recognized by the white precipitate given by nitrate of silver after acidifying with pure nitric acid4 ,the strength of commercial ammonia varies greatly2 that sold for pharmaceutica purposes1 under the name of liquor ammoni1 contains about #aj per cent1 of real ammonia4 ,the sp4 gr4 of aqueous ammonia diminishes with the proportion of ammonia present1 the liquor ammoni being usually about #icf4 ,chemical ,properties4--,ammonia1 although forming a large class of salts1 appears at first sight to contrast strongly by composition with the alkalies proper1 such as potash and soda4 ,mineral bases generally are protoxides of metals1 but ammonia consists simply of nitrogen and hydrogen united with oxygen4 ,the following remarks may perhaps tend somewhat to elucidate the difficulty3-- ,theory of ,ammonium4--,this theory supposes that a substance exists possessing the properties of a metal1 but different from metallic bodies generally in being compound in structure3 the formula assigned to it is ,,nh#d1 #a atom of nitrogen united with #d of hydrogen4 ,the hypothetical metal is termed ammonium1 and ammonia1 associated with an atom of water1 may be viewed as its oxide2 for ,,nh#c ,,ho plainly equals ,,nh#d,o4 ,thus1 as potash is the oxide of potassium1 so ammonia is the oxide of ammonium4 ,the composition of the salts of ammonia is on this view assimilated to those of the alkalies proper4 ,thus1 sulphate of ammonia is a sulphate of the oxide of ammonium2 muriate or hydrochlorate of ammonia is a chloride of ammonium1 etc4 ,ammonio-,nitrate of ,silver4 7,see ,silver1 ,ammonio-,nitrate of47 ,aqua-,regia4 7,see ,nitro-,hydrochloric ,acid47 ,baryta1 ,nitrate of4 7,see ,nitrate of ,baryta47 ,bichloride of ,mercury4 7,see ,mercury1 ,bichloride of47 ,bromine4 ,symbol1 ,br4 ,atomic weight1 #gh4 ,this elementary substance is obtained from the uncrystallizable residuum of sea-water1 termed bittern4 ,it exists in the water in very minute proportion1 combined with magnesium in the form of a soluble bromide of magnesium4 ,properties4--,bromine is a deep reddish-brown liquid of a disagreeable odor1 and fuming strongly at common temperatures2 sparingly soluble in water 7#a part in #bc1 ,lowig71 but more abundantly so in alcohol1 and especially in ether4 ,it is very heavy1 having a specific gravity of #cj4 ,bromine is closely analogous to chlorine and iodine in its chemical properties4 ,it stands on the list intermediately between the two2 its affinities being stronger than those of iodine1 but weaker than chlorine4 7,see chlorine47 ,it forms a large class of salts1 of which the bromides of potassium1 cadmium1 and silver are the most familiar to photographers4 ,bromide of ,potassium4 ,symbol1 ,k,br4 ,atomic weight1 #aah4 ,bromide of potassium is prepared by adding bromine to caustic potash1 and heating the product1 which is a mixture of bromide of potassium and bromate of potash1 to redness1 in order to drive off the oxygen from the latter salt4 ,it crystallizes in anhydrous cubes1 like the chloride1 and iodide1 of potassium2 it is easily soluble in water1 but more sparingly so in alcohol2 it yields red fumes of bromine when acted upon by sulphuric acid4 ,bromide of ,silver4 7,see ,silver1 ,bromide of47 ,carbonate of ,soda4 ,symbol1 ,na,o ,,co#b #aj ,aq4 ,this salt was formerly obtained from the ashes of seaweeds1 but is now more economically manufactured on a large scale from common salt4 ,the chloride of sodium is first converted into sulphate of soda1 and afterwards the sulphate into carbonate of soda4 ,properties4--,the perfect crystals contain ten atoms of water1 which are driven off by the application of heat1 leaving a white powder--the anhydrous carbonate4 ,common washing soda is a neutral carbonate1 contaminated to a certain extent with chloride of sodium and sulphate of soda4 ,the carbonate used for effervescing draughts is either a bicarbonate with #a atom of water1 or a sesquicarbonate1 containing about #dj per cent1 of real alkali2 it is therefore nearly double as strong as the washing carbonate1 which contains about #bb per cent1 of soda4 ,carbonate of soda is soluble in twice its weight of water at #fj1 the solution being strongly alkaline4 ,carbonate of ,potash4 7,see ,potash1 ,carbonate of47 ,caseine4 7,see ,milk47 ,charcoal1 ,animal4 ,animal charcoal is obtained by heating animal substances1 such as bones1 dried blood1 horns1 etc41 to redness1 in close vessels1 until all volatile empyreumatic matters have been driven off1 and a residue of carbon remains4 ,when prepared from bones it contains a large quantity of inorganic matter in the shape of carbonate and phosphate of lime1 the former of which produces alkalinity in reacting upon nitrate of silver4 ,animal charcoal is freed from these earthy salts by repeated digestion in hydrochloric acid2 but unless very carefully washed it is apt to retain an acid reaction1 and so to liberate free nitric acid when added to solution of nitrate of silver4 ,properties4--,animal charcoal1 when pure1 consists solely of carbon1 and burns away in the air without leaving any residue3 it is remarkable for its property of decolorizing solutions2 the organic coloring substance being separated1 but not actually destroyed1 as it is by chlorine employed as a bleaching agent4 ,this power of absorbing coloring matter is not possessed in an equal degree by all varieties of charcoal1 but is in great measure peculiar to those derived from the animal kingdom4 ,china ,clay or ,kaolin4 ,this is prepared1 by careful levigation1 from mouldering granite and other disintegrated felspathic rocks4 ,it consists of the silicate of alumina1--that is1 of silicic acid or flint1 which is an oxide of silicon1 united with the base alumina 7oxide of aluminum74 ,kaolin is perfectly insoluble in water and acids1 and produces no decomposition in solution of nitrate of silver4 ,it is employed by photographers to decolorize solutions of nitrate of silver which have become brown from the action of albumen or other organic matters4 ,chlorine4 ,symbol1 ,cl4 ,atomic weight1 #cf4 ,chlorine is a chemical element found abundantly in nature1 combined with metallic sodium in the form of chloride of sodium1 or sea-salt4 ,preparation4--,by distilling common salt with sulphuric acid1 sulphate of soda and hydrochloric acid are formed4 ,hydrochloric acid contains chlorine combined with hydrogen2 by the action of nascent oxygen 7see oxygen71 the hydrogen may be removed in the form of water1 and the chlorine left alone4 ,properties4--,chlorine is a greenish-yellow gas1 of a pungent and suffocating odor2 soluble to a considerable extent in water1 the solution possessing the odor and color of the gas4 ,it is nearly #b-a_/b times as heavy as a corresponding bulk of atmospheric air4 ,chemical ,properties4--,chlorine belongs to a small natural group of elements which contains also bromine1 iodine1 and fluorine4 ,they are characterized by having a strong affinity for hydrogen1 and also for the metals1 but are comparatively indifferent to oxygen4 ,many metallic substances actually undergo combustion when projected into an atmosphere of chlorine1 the union between the two taking place with extreme violence4 ,the characteristic bleaching properties of chlorine gas are explained in the same manner3--,hydrogen is removed from the organic substance1 and in that way the structure is broken up and the color destroyed4 ,chlorine is more powerful in its affinities than either bromine or iodine4 ,the salts formed by these three elements are closely analogous in composition and often in properties4 ,those of the alkalies1 alkaline earths1 and many of the metals are soluble in water1 but the silver salts are insoluble2 the lead salts sparingly so4 ,the combinations of chlorine1 bromine1 iodine1 and fluorine1 with hydrogen1 are acids1 and neutralize alkalies in the usual manner1 with formation of alkaline chloride and water4 ,the test by which the presence of chlorine is detected1 either free or in combination with bases1 is nitrate of silver2 it gives a white curdy precipitate of chloride of silver1 insoluble in nitric acid1 but soluble in ammonia4 ,the solution of nitrate of silver employed as the test must not contain iodide of silver1 as this compound is precipitated by dilution4 ,chloride of ,ammonium4 ,symbol1 ,,nh#d;,cl4 ,atomic weight1 #ed4 ,this salt1 also known as muriate or hydrochlorate of ammonia1 occurs in commerce in the form of colorless and translucent masses1 which are procured by sublimation1 the dry salt being volatile when strongly heated4 ,it dissolves in an equal weight of boiling1 or in three parts of cold water4 ,it contains more chlorine in proportion to the weight used than chloride of sodium1 the atomic weights of the two being as #ed to #fj4 ,chloride of ,barium4 ,symbol1 ,ba,cl#b;,,ho4 ,atomic weight1 #abc4 ,barium is a metallic element1 very closely allied to calcium1 the elementary basis of lime4 ,the chloride of barium is commonly employed as a test for sulphuric acid1 with which it forms an insoluble precipitate of sulphate of baryta4 ,it is also said to affect the color of the photographic image when used in preparing positive paper2 which may possibly be due to a chemical combination of baryta with albumen3 but it must be remembered that this chloride1 from its high atomic weight1 contains less chlorine than the alkaline chlorides4 ,properties of ,chloride of ,barium4--,chloride of barium occurs in the form of white crystals1 soluble in about two parts of water1 at common temperature4 ,these crystals contain two atoms of water of crystallization1 which are expelled at #bab1 leaving the anhydrous chloride4 ,chloride of ,gold4 7,see ,gold1 ,chloride of47 ,chloride of ,sodium4 ,symbol1 ,na,cl4 ,atomic weight1 #fj4 ,common salt exists abundantly in nature1 both in the form of solid rock-salt and dissolved in the waters of the ocean4 ,properties of the pure ,salt4--,fusible without decomposition at low redness1 but sublimes at higher temperatures2 the melted salt concretes into a hard white mass on cooling4 ,nearly insoluble in absolute alcohol1 but dissolves in minute quantity in rectified spirit4 ,soluble in three parts of water1 both hot and cold4 ,crystallizes in cubes1 which are anhydrous4 ,impurities of ,common ,salt4--,table salt often contains large quantities of the chlorides of magnesium and calcium1 which1 being deliquescent1 produce a dampness by absorption of atmospheric moisture3 sulphate of soda is also commonly present4 ,the salt may be purified by repeated recrystallization1 but it is more simple to prepare the pure compound directly1 by neutralizing hydrochloric acid with carbonate of soda4 ,chloride of ,silver4 7,see ,silver1 ,chloride of47 ,citric ,acid4 ,this acid is found abundantly in lemon-juice and in lime-juice4 ,it occurs in commerce in the form of large crystals1 which are soluble in less than their own weight of water at #fj4 ,commercial citric acid is sometimes mixed with tartaric acid4 ,the adulteration may be discovered by making a concentrated solution of the acid and adding acetate of potash2 crystals of bitartrate of potash will separate if tartaric acid be present4 ,citric acid is tribasic4 ,it forms with silver a white insoluble salt1 containing #c atoms of oxide of silver to #a atom of citric acid4 ,if the citrate of silver be heated in a current of hydrogen gas1 a part of the acid is liberated and the salt is reduced to a citrate of suboxide of silver2 which is of a red color4 ,the action of white light in reddening citrate of silver is shown by the author to be of a similar nature4 ,cyanide of ,potassium4 ,symbol1 ,k1 ,c#b,n1 or ,k,cy4 ,atomic weight1 #ff4 ,this salt is a compound of cyanogen gas with the metal potassium4 ,cyanogen is not an elementary body1 like chlorine or iodine1 but consists of carbon and nitrogen united in a peculiar manner4 ,although a compound substance1 it reacts in the manner of an element1 and is therefore 7like ammonium1 previously described7 an exception to the usual laws of chemistry4 ,many other bodies of a similar character are known4 ,ether4 ,symbol1 ,c#d;,h#e,o4 ,atomic weight1 #cg4 ,ether is obtained by distilling a mixture of sulphuric acid and alcohol4 ,if the formula of alcohol 7,c#d;,h#f,o#b7 be compared with that of ether1 it will be seen to differ from it in the possession of an additional atom of hydrogen and of oxygen3 in the reaction1 the sulphuric acid removes these elements in the form of water1 and by so doing converts one atom of alcohol into an atom of ether4 ,the term sulphuric applied to the commercial ether has reference only to the manner of its formation4 ,properties of ,ether4--,it is neither acid nor alkaline to test-paper4 ,specific gravity1 at #fj1 about #gbj4 ,boils at #ih ,fahrenheit4 ,the vapor is exceedingly dense1 and may be seen passing off from the liquid and falling to the ground3 hence the danger of pouring ether from one bottle to another if a flame be near at hand4 ,ether does not mix with water in all proportions2 if the two are shaken together1 after a short time the former rises and floats upon the surface4 ,in this way a mixture of ether and alcohol may be purified to some extent1 as in the common process of washing ether4 ,the water employed however always retains a certain portion of ether 7about a tenth part of its bulk71 and acquires a strong ethereal odor2 washed ether also contains water in small quantity4 ,bromine and iodine are both soluble in ether1 and gradually react upon and decompose it4 ,the strong alkalies1 such as potash and soda1 also decompose ether slightly after a time1 but not immediately4 ,exposed to air and light1 ether is oxidized and acquires a peculiar odor4 ,ether dissolves fatty and resinous substances readily1 but inorganic salts are mostly insoluble in this fluid4 ,hence it is that iodide of potassium and other substances dissolved in alcohol are precipitated to a certain extent by the addition of ether4 ,fluoride of ,potassium4 ,symbol1 ,,kf4 ,atomic weight1 #ei4 ,preparation4--,fluoride of potassium is formed by saturating hydrofluoric acid with potash1 and evaporating to dryness in a platinum vessel4 ,hydrofluoric acid contains fluorine combined with hydrogen2 it is a powerfully acid and corrosive liquid1 formed by decomposing flour spar1 which is a fluoride of calcium1 with strong sulphuric acid2 the action which takes place being precisely analogous to that involved in the preparation of hydrochloric acid4 ,properties4--,a deliquescent salt1 occurring in small and imperfect crystals4 ,very soluble in water3 the solution acting upon glass in the same manner as hydrofluoric acid4 ,formic ,acid4 ,symbol1 ,c#b;,,ho#c4 ,atomic weight1 #cg4 ,this substance was originally discovered in the red ant 7,formica rufa71 but it is prepared on a large scale by distilling starch with binoxide of manganese and sulphuric acid4 ,properties4--,the strength of commercial formic acid is uncertain1 but it is always more or less dilute4 ,the strongest acid1 as obtained by distilling formiate of soda with sulphuric acid1 is a fuming liquid with a pungent odor1 and containing only one atom of water3 it inflames the skin in the same manner as the sting of the ant4 ,formic acid reduces the oxides of gold1 silver1 and mercury1 to the metallic state1 and is itself oxidized into carbonic acid4 ,the alkaline formiates also possess the same properties4 ,gelatine4 ,symbol1 ,c#ac;,h#aj,o#e,n#b4 ,atomic weight1 #aef4 ,this is an organic substance somewhat analogous to albumen1 but differing from it in properties4 ,it is obtained by subjecting bones1 hoofs1 horns1 calves' feet1 etc41 to the action of boiling water4 ,the jelly formed on cooling is termed size1 or when dried or cut into slices1 glue4 ,gelatine1 as it is sold in the shops1 is a pure form of glue4 ,isinglass is gelatine prepared1 chiefly in ,russia1 from the air-bladders of certain species of sturgeon4 ,properties of ,gelatine4--,gelatine softens and swells up in cold water1 but does not dissolve until heated3 the hot solution1 on cooling1 forms a tremulous jelly4 ,one ounce f cold water will retain about three grains of isinglass without gelatinizing2 but much depends upon the temperature1 a few degrees greatly affecting the result4 ,gelatine forms no compound with oxide of silver analogous to the albuminate of silver2 which fact explains the difference in the photographic properties of albumen and gelatine4 ,glycerine4 ,fatty bodies are resolved by treatment with an alkali into an acid--which combines with the alkali1 forming a soap1--and glycerine1 remaining in solution4 ,pure glycerine1 as obtained by ,price's patent process of distillation1 is a viscid liquid of sp4 gr4 about #abc2 miscible in all proportions with water and alcohol4 ,it is peculiarly a neutral substance1 exhibiting no tendency to combine with acids or bases4 ,it has little or no action upon nitrate of silver in the dark1 and reduces it very slowly even when exposed to light4 ,gold1 ,chloride of4 ,symbol1 ,au,cl#c4 ,atomic weight1 #cjc4 ,this salt is formed by dissolving pure metallic gold in nitro-hydrochloric acid1 and evaporating at a gentle heat4 ,the solution affords deliquescent crystals of a deep orange color4 ,chloride of gold1 in a state fit for photographic use may easily be obtained by the following process3--,place a half-sovereign in any convenient vessel1 and pour on it half a drachm of nitric acid mixed with two and a half drachms of hydrochloric acid and three drachms of water2 digest by a gentle heat1 but do not boil the acid1 or much of the chlorine will be driven off in the form of gas4 ,at the expiration of a few hours add fresh aqua-regia in quantity the same as at first1 which will probably complete the solution1 but if not1 repeat the process a third time4 ,lastly1 neutralize the liquid by adding carbonate of soda until all effervescence ceases1 and a green precipitate forms2 this is carbonate of copper1 which must be allowed several hours to separate thoroughly4 ,the solution then contains chloride of gold in a neutral state1 and free from copper and silver1 with which the metallic gold is alloyed in the standard coin of the realm4 ,the weight of a half-sovereign is about #fa grains1 of which #ef grains are pure gold4 ,this is equivalent to #hf grains of chloride of gold1 which will therefore be the quantity contained in the solution4 ,the following process for preparing chloride of gold is more perfect than the last3--dissolve the gold coin in aqua-regia as before2 then boil with excess of hydrochloric acid to destroy the nitric acid1 dilute largely with distilled water1 and add a filtered aqueous solution of common sulphate of iron 7#f parts in #a part of gold72 collect the precipitated gold1 which is now free from copper2 re-dissolve in aqua-regia1 and evaporate to dryness on a water bath4 ,avoid using ammonia to neutralize chloride of gold1 as it would be liable to occasion a deposit of fulminating gold1 the properties of which are described immediately following4 ,properties of ,chloride of ,gold4--,as sold in commerce it usually contains excess of hydrochloric acid1 and is then of a bright yellow color2 but when neutral and somewhat concentrated it is dark red 7,leo ruber of the alchemists74 ,it gives no precipitate with carbonate of soda1 unless heat be applied2 the free hydrochloric acid present forms1 with the alkali1 chloride of sodium1 which unites with the chloride of gold1 and produces a double salt1 chloride of gold and sodium1 soluble in water4 ,chloride of gold is decomposed with precipitation of metallic gold by charcoal1 sulphurous acid1 and many of the vegetable acids2 also by protosulphate and protonitrate of iron4 ,it tinges the cuticle of an indelible purple tint4 ,it is soluble in alcohol and in ether4 ,gold1 ,fulminating4 ,this is a yellowish-brown substance1 precipitated on adding ammonia to a strong solution of chloride of gold4 ,it may be dried carefully at #bab1 but explodes violently on being heated suddenly about to #bij4 ,friction also causes it to explode when dry2 but the moist powder may be rubbed or handled without danger4 ,it is decomposed by sulphuretted hydrogen4 ,fulminating gold is probably an aurate of ammonia1 containing #b atoms of ammonia to #a atom of peroxide of gold4 ,gold1 ,hyposulphite of4 ,symbol1 ,au,o ,s#b,o#b4 ,atomic ,weight1 #bec4 ,hyposulphite of gold is produced by the reaction of chloride of gold upon hyposulphite of soda4 ,the salt sold in commerce as sel d'or is a double hyposulphite of gold and soda1 containing one atom of the former salt to three of the latter1 with four atoms of water of crystallization4 ,it is formed by adding one part of chloride of gold1 in solution1 to three parts of hyposulphite of soda1 and precipitating the resulting salt by alcohol2 the chloride of gold must be added to the hyposulphite of soda1 and not the soda salt to the gold4 ,properties4--,hyposulphite of gold is unstable and cannot exist in an isolated state1 quickly passing into sulphur1 sulphuric acid1 and metallic gold4 ,when combined with excess of hyposulphite of soda in the form of sel d'or1 it is more permanent4 ,sel d'or occurs crystallized in fine needles1 which are very soluble in water4 ,the commercial article is often impure1 containing little else than hyposulphite of soda1 with a trace of gold4 ,it may be analyzed by adding a few drops of strong nitric acid 7free from chlorine7 diluting with water1 and afterwards collecting and igniting the yellow powder1 which is metallic gold4 ,grape ,sugar4 ,symbol1 ,c#bd;,h#bh,o#bh4 ,atomic weight1 #cff4 ,this modification of sugar1 often termed granular sugar1 or glucose1 exists abundantly in the juice of grapes1 and in many other varieties of fruit4 ,it forms the saccharine concretion found in honey1 raisins1 dried figs1 etc4 ,it may be produced artificially by the action of fermenting principles1 and of dilute mineral acids1 upon starch4 ,properties4--,grape sugar crystallizes slowly and with difficulty from a concentrated aqueous solution1 in small hemispherical nodules1 which are hard1 and feel gritty between the teeth4 ,it is much less sweet to the taste than cane sugar1 and not so soluble in ,water 7#a part dissolves in #a-a_/b of cold water74 ,grape sugar tends to absorb oxygen1 and hence it possesses the property of decomposing the salts of the noble metals1 and reducing them by degrees to the metallic state1 even without the aid of lights ,the action however in the case of nitrate of silver is slow1 unless the temperature be somewhat elevated4 ,cane sugar does not possess these properties to an equal extent1 and hence it is readily distinguished from the other variety4 ,honey4 ,this substance contains two distinct kinds of sugar1 grape sugar1 and an uncrystallizable substance analogous to1 or identical with1 the treacle found associated with common sugar in the cane juice4 ,the agreeable taste of honey probably depends upon the latter1 but its reducing power on metallic oxides is due to the former4 ,pure grape sugar can readily be obtained from inspissated honey1 by treating it with alcohol1 which dissolves out the syrup1 but leaves the crystalline portion4 ,hydrochloric2 ,acid4 ,symbol1 ,h,cl4 ,atomic weight1 #cg4 ,hydrochloric acid is a volatile gas1 ,which may be liberated from the salts termed chlorides by the action of sulphuric acid4 ,the acid1 by its superior affinities1 removes the base2 thus1-- ,na,cl ,,ho ,,so#c ,na,o ,,so#c ,h,cl4 ,properties4--,abundantly soluble in water1 forming the liquid hydrochloric or muriatic acid of commerce4 ,the most concentrated solution of hydrochloric acid has a sp4 gr4 #ab1 and contains about #dj per cent1 of gas2 that commonly sold is somewhat weaker1 sp2 gr4 #aad #bh per cent4 real acid4 ,pure hydrochloric acid is colorless1 and fumes in the air4 ,the yellow color of the commercial acid depends upon the presence of traces of perchloride of iron or organic matter2 commercial muriatic acid also often contains a portion of free chlorine and of sulphuric acid4 ,hydriodic ,acid4 ,symbol1 ,,hi4 ,atomic weight1 #abg4 ,this is a gaseous compound of hydrogen and iodine1 corresponding in composition to the hydrochloric acid4 ,it cannot1 however1 from its instability1 be obtained in the same manner1 since1 on distilling an iodide with sulphuric acid1 the hydriodic acid first formed is subsequently decomposed into iodine and hydrogen4 ,an aqueous solution of hydriodic acid is easily prepared by adding iodine to water containing sulphuretted hydrogen gas2 a decomposition takes place1 and sulphur is set free2 thus3 ,,hs ,i ,,hi ,s4 ,properties4--,hydriodic acid is very soluble in water1 yielding a strongly acid liquid4 ,the solution1 colorless at first1 soon becomes brown from decomposition1 and liberation of free iodine4 ,it may be restored to its original condition by adding solution of sulphuretted hydrogen4 ,hydrosulphuric ,acid4 ,symbol1 ,,hs4 ,atomic weighty #ag4 ,this substance1 also known as sulphuretted hydrogen1 is a gaseous compound of sulphur and hydrogen1 analogous in composition to hydrochloric and hydriodic acids4 ,it is usually prepared by the action of dilute sulphuric acid upon sulphuret of iron1 the decomposition being similar to that involved in the preparation of the hydrogen acids generally3-- ,fe,s ,,ho ,,so#c ,fe,o ,,so#c ,,hs4 ,properties4--,cold water absorbs three times its bulk of hydrosulphuric acid1 and acquires the peculiar putrid odor and poisonous qualities of the gas4 ,the solution is faintly acid to test-paper1 and becomes opalescent on keeping1 from gradual separation of sulphur4 ,it is decomposed by nitric acid1 and also by chlorine and iodine4 ,it precipitates silver from its solutions1 in the form of black sulphuret of silver2 also copper1 mercury1 lead1 etc42 but iron and other metals of that class are not affected1 if the liquid contains free acid4 ,hydrosulphuric acid is constantly employed in the chemical laboratory for these and other purposes4 ,hydrosulphate of ,ammonia4 ,symbol1 ,,nh#d,s ,,hs4 ,atomic weight1 #ea4 ,the liquid known by this name1 and formed by passing sulphuretted hydrogen gas into ammonia1 is a double sulphuret of hydrogen and ammonium4 ,in the preparation1 the passage of the gas is to be continued until the solution gives no precipitate with sulphate of magnesia and smells strongly of hydrosulphuric acid4 ,properties1--,colorless at first1 but afterwards changes to yellow1 from liberation and subsequent solution of sulphur4 ,becomes milky on the addition of any acid4 ,precipitates1 in the form of sulphuret1 all the metals which are affected by sulphuretted hydrogen2 and1 in addition1 those of the class to which iron1 zinc1 and manganese1 belong4 ,hydrosulphate of ammonia is employed in photography to darken the negative image1 and also in the preparation of iodide of ammonium2 the separation of silver from hyposulphite solutions1 etc4 ,hyposulphite of ,soda4 ,symbol1 ,na,o ,s#b;,h#b #e ,,ho4 ,atomic weight1 #abe4 ,the hyposulphite of soda commonly employed by photographers is a neutral combination of hyposulphurous acid and the alkali soda4 ,it is selected as being more economical in preparation than any other hyposulphite adapted for fixing4 ,hyposulphite of soda occurs in the form of large translucent groups of crystals1 which include five atoms of water4 ,these crystals are soluble in water almost to any extent1 the solution being attended with the production of cold2 they have a nauseous and bitter taste4 ,hyposulphite of ,gold4 7,see ,gold1 ,hyposulphite of47 ,hyposulphite of ,silver4 7,see ,silver1 ,hyposulphite of47 ,iceland ,moss4 ,cetraria ,islandica4--,a species of lichen found in ,iceland and the mountainous parts of ,europe2 when boiled in water1 it first swells up1 and then yields a substance which gelatinizes on cooling4 ,it contains lichen starch2 a bitter principle soluble in alcohol1 termed cetrarine2 and common starch2 traces of gallic acid and bitartrate of potash are also present4 ,iodine4 ,symbol1 ,i4 ,atomic weight1 #abf4 ,iodine is chiefly prepared at ,glasgow1 from kelp1 which is the fused ash obtained by burning seaweeds4 ,the waters of the ocean contain minute quantities of the iodides of sodium and magnesium1 which are separated and stored up by the growing tissues of the marine plant4 ,in the preparation1 the mother-liquor of kelp is evaporated to dryness and distilled with sulphuric acid2 the hydriodic acid first liberated is decomposed by the high temperature1 and fumes of iodine condense in the form of opaque crystals4 ,properties4--,iodine has a bluish-black color and metallic lustre2 it stains the skin yellow1 and has a pungent smell1 like diluted chlorine4 ,it is extremely volatile when moist1 boils at #cej1 and produces dense violet-colored fumes1 which condense in brilliant plates4 ,specific gravity #didf4 ,iodine is very sparingly soluble in water1 #a part requiring #gjjj parts for perfect solution3 even this minute quantity however tinges the liquid of a brown color4 ,alcohol and ether dissolve it more abundantly1 forming dark-brown solutions4 ,iodine also dissolves freely in solutions of the alkaline iodides1 such as the iodide of potassium1 of sodium1 and of ammonium4 ,chemical ,properties4--,iodine belongs to the chlorine group of elements1 characterized by forming acids with hydrogen1 and combining extensively with the metals 7see chlorine74 ,they are however comparatively indifferent to oxygen1 and also to each other4 ,the iodides of the alkalies and alkaline earths are soluble in water2 also those of iron1 zinc1 cadmium1 etc4 ,the iodides of lead1 silver1 and mercury are nearly or quite insoluble4 ,iodine possesses the property of forming a compound of a deep blue color with starch4 ,in using this as a test1 it is necessary first to liberate the iodine 7if in combination71 by means of chlorine1 or nitric acid saturated with peroxide of nitrogen4 ,the presence of alcohol or ether interferes to a certain extent with the result4 ,iodide of ,ammonium4 ,symbol1 ,,nh#d;,i4 ,atomic weight1 #add4 ,this salt may be prepared by adding carbonate of ammonia to iodide of iron1 but more easily by the following process3--,a strong solution of hydrosulphate of ammonia is first made1 by passing sulphuretted hydrogen gas into liquor ammoni ,to this liquid iodine is added until the whole of the sulphuret of ammonium has been converted into iodide4 ,when this point is reached1 the solution at once colors brown from solution of free iodine4 ,on the first addition of the iodine1 an escape of sulphuretted hydrogen gas and a dense deposit of sulphur take place4 ,after the decomposition of the hydrosulphate of ammonia is complete1 a portion of hydriodic acid--formed by the mutual reaction of sulphuretted hydrogen and iodine--attacks any carbonate of ammonia which may be present1 and causes an effervescence4 ,the effervescence being over1 the liquid is still acid to test-paper1 from excess of hydriodic acid2 it is to be cautiously neutralized with ammonia1 and evaporated by the heat of a water-bath to the crystallizing point4 ,the crystals should be thoroughly dried over a dish of sulphuric acid1 and then sealed in small tubes containing each about half a drachm of the salt2 by this means it will be preserved colorless4 ,iodide of ammonium is very soluble in alcohol1 but it is not advisable to keep it in solution1 from the rapidity with which it decomposes and becomes brown4 ,the most common impurity of commercial iodide of ammonium is sulphate of ammonia2 it is detected by its sparing insolubility in alcohol4 ,iodide of ,cadmium4 ,symbol1 ,cd,i4 ,atomic weight1 #ahb4 ,this salt is formed by heating filings of metallic cadmium with iodine1 or by mixing the two together with addition of water4 ,it is useful in iodizing collodion intended for keeping1 since it does not become brown from liberation of free iodine with the same rapidity as the alkaline iodides4 ,iodide of cadmium is very soluble both in alcohol and water2 the solution yielding on evaporation large six-sided tables of a pearly lustre1 which are permanent in the air4 ,the crystalline form of this salt is a sufficient criterion of its purity4 ,iodide of ,iron4 ,symbol1 ,fe,i4 ,atomic weight1 #aed4 ,iodide of iron1 in a fit state for photographic use1 is easily obtained by dissolving a drachm of iodine in an ounce of proof spirit--that is1 a mixture of equal bulks of spirits of wine and water--and adding an excess of iron filings4 ,after a few hours1 a green solution is obtained without the aid of heat4 ,the presence of metallic iron in excess prevents the liberation of iodine and deposit of peroxide of iron which would otherwise speedily occur4 ,it is very soluble in water and alcohol1 but the solution rapidly absorbs oxygen and deposits peroxide of iron2 hence the importance of preserving it in contact with metallic iron1 with which the separated iodine may recombine4 ,by very careful evaporation1 hydrated crystals of protoiodide may be obtained1 but the composition of the solid salt usually sold under that name cannot be depended on4 ,the periodide of iron1 corresponding to the perchloride1 has not been examined1 and it is doubtful if any such compound exists4 ,iodide of ,potassium4 ,symbol1 ,,ki4 ,atomic weight1 #aff4 ,this salt is usually formed by dissolving iodine in solution of potash until it begins to acquire a brown color2 a mixture of iodide of potassium and iodate of potash 7,,ko ,,io#e7 is thus formed2 but by evaporation and heating to redness1 the latter salt parts with its oxygen1 and is converted into iodide of potassium4 ,properties4--,it forms cubic and prismatic crystals1 which should be hard1 and very slightly or not at all deliquescent4 ,soluble in less than an equal weight of water at #fj2 it is also soluble in alcohol1 but not in ether4 ,the proportion of iodide of potassium contained in a saturated alcoholic solution1 varies with the strength of the spirit1--with common spirits of wine1 sp4 gr4 #hcf1 it would be about #h grains to the drachm2 with alcohol rectified from carbonate of potash1 sp4 gr4 #hbc1 #d or #e grains3 with absolute alcohol1 #a to #b grains4 ,the solution of iodide of potassium is instantly colored brown by free chlorine2 also very rapidly by peroxide of nitrogen2 ordinary acids1 however1 act less quickly1 hydriodic acid being first formed1 and subsequently decomposing spontaneously4 ,iodide of potassium1 as sold in the shops1 is often contaminated with various impurities4 ,the first and most remarkable is carbonate of potash4 ,when a sample of iodide of potassium contains much carbonate of potash1 it forms small and imperfect crystals1 which are strongly alkaline to test-paper1 and become moist on exposure to the air1 from the deliquescent nature of the alkaline carbonate4 ,sulphate of potash is also a common impurity2 it may be detected by chloride of barium4 ,chloride of potassium is another impurity2 it is detected as follows3--,precipitate the salt by an equal weight of nitrate of silver1 and treat the yellow mass with solution of ammonia2 if any chloride of silver is present1 it dissolves in the ammonia1 and after nitration is re-precipitated in white curds by the addition of an excess of pure nitric acid4 ,if the nitric acid employed is not pure1 but contains traces of free chlorine1 the iodide of silver must be well washed with distilled water before treating it with ammonia1 or the excess of free nitrate of silver dissolving in the ammonia would1 on neutralizing1 produce chloride of silver1 and so cause an error4 ,iodide of potash is a fourth impurity often found in iodide of potassium3 to detect it1 add a drop of dilute sulphuric acid1 or a crystal of citric acid1 to the solution of the iodide2 when1 if much iodate be present1 the liquid will become yellow from liberation of free iodine4 ,the rationale of this reaction is as follows3--,the sulphuric acid unites with the base of the salt1 and liberates hydriodic acid 7,,hi71 a colorless compound2 but if iodic acid 7,,io#e7 be also present1 it decomposes the hydriodic acid first formed1 oxidizing the hydrogen into water 7,,ho71 and setting free the iodine4 ,the immediate production of a yellow color on adding a weak acid to aqueous solution of iodide of potassium is1 therefore1 a proof of the presence of an iodate4 ,as iodate of potash is thought to render collodion insensitive 7871 this point should be attended to4 ,iodide of potassium may be rendered very pure by recrystallizing from spirit1 or by dissolving in strong alcohol of sp4 gr4 #hbc1 in which sulphate1 carbonate1 and iodate of potash are insoluble4 ,the proportion of iodide of potassium contained in saturated alcoholic solutions varies with the strength of the spirit4 ,solution of chloride of barium is commonly used to detect impurities in iodide of potassium2 it forms a white precipitate if carbonate1 iodate1 or sulphate be present4 ,in the two former cases the precipitate dissolves on the addition of pure dilute nitric acid1 but in the latter it is insoluble4 ,the commercial iodide1 however1 is rarely so pure as to remain quite clear on the addition of chloride of barium1 a mere opalescence1 therefore1 may be disregarded4 ,iodide of ,silver4 7,see ,silver1 ,iodide of47 ,iron1 ,protosulphate of4 ,symbol1 ,fe,o ,,so#c #g ,,ho4 ,atomic weight1 #aci4 ,this salt1 often termed copperas or green vitriol1 is a most abundant substance1 and used for a variety of purposes in the arts4 ,commercial sulphate of iron1 however1 being prepared on a large scale1 requires recrystallization to render it sufficiently pure for photographic purposes4 ,pure sulphate of iron occurs in the form of large1 transparent prismatic crystals1 of a delicate green color3 by exposure to the air they gradually absorb oxygen and become rusty on the surface4 ,solution of sulphate of iron1 colorless at first1 afterwards changes to a red tint1 and deposits a brown powder2 this powder is a basic persulphate of iron1 that is1 a persulphate containing an excess of the oxide or base4 ,by the addition of sulphuric or acetic acid to the solution1 the formation of a deposit is prevented1 the brown powder being soluble in acid liquids4 ,the crystals of sulphate of iron include a large quantity of water of crystallization1 a part of which they lose by exposure to dry air4 ,by a higher temperature1 the salt may be rendered perfectly anhydrous1 in which state it forms a white powder4 ,aqueous solution of sulphate of iron absorbs the binoxide of nitrogen1 acquiring a deep olive-brown color3 as this gaseous binoxide is itself a reducing agent1 the liquid so formed has been proposed as a more energetic developer than the sulphate of iron alone4 ,iron1 ,protonitrate of4 ,symbol1 ,fe,o ,,no#e #g ,,ho4 ,atomic weight1 #aec4 ,this salt1 by careful evaporation in vacuo over sulphuric acid1 forms transparent crystals1 of a light green color1 and containing #g atoms of water1 like the protosulphate4 ,it is exceedingly unstable1 and soon becomes red from decomposition1 unless preserved from contact with air4 ,the following process is commonly followed for preparing protonitrate of iron3-- ,take of nitrate of baryta #cjj grains2 powder and dissolve by the aid of heat in three ounces of water2 then throw in1 by degrees1 with constant stirring1 crystallized sulphate of iron1 powdered1 #cbj grains4 ,continue to stir for about five or ten minutes4 ,allow to cool1 and filter from the white deposit1 which is the insoluble sulphate of baryta4 ,in place of nitrate of baryta1 the nitrate of lead may be used 7sulphate of lead being an insoluble salt71 but the quantity required will be different4 ,the atomic weights of nitrate of baryta and nitrate of lead are as #aca to #aff2 consequently #cjj grains of the former are equivalent to #chj grains of the latter4 ,iron1 ,perchloride of4 ,symbol1 ,fe#b;,cl#c4 ,atomic weight1 #afd4 ,there are two chlorides of iron1 corresponding in composition to the protoxide and the sesquioxide respectively4 ,the protochloride is very soluble in water1 forming a green solution1 which precipitates a dirty white protoxide on the addition of an alkali4 ,the perchloride1 on the other hand1 is dark brown1 and gives a foxy-red precipitate with alkalies4 ,properties4--,perchloride of iron may be obtained in the solid form by heating iron wire in excess of chlorine2 it condenses in the shape of brilliant and iridescent brown crystals1 which are volatile1 and dissolve in water1 the solution being acid to test-paper4 ,it is also soluble in alcohol1 forming the tinctura ferri sesquichloridi of the ,pharmacopoeia4 ,commercial perchloride of iron ordinarily contains an excess of hydrochloric acid4 ,litmus4 ,litmus is a vegetable substance1 prepared from various lichens1 which are principally collected on rocks adjoining the sea4 ,the coloring matter is extracted by a peculiar process1 and afterwards made up into a paste with chalk1 plaster of ,paris1 c4 ,litmus occurs in commerce in the form of small cubes1 of a fine violet color4 ,in using it for the preparation of test-papers1 it is digested in hot water1 and sheets of porous paper are soaked in the blue liquid so formed4 ,the red papers are prepared at first in the same manner1 but afterwards placed in water which has been rendered faintly acid with sulphuric or hydrochloric acid4 ,mercury1 ,bichloride of4 ,symbol1 ,hg,cl#b4 ,atomic weight1 #bgd4 ,this salt1 also called corrosive sublimate1 and sometimes chloride of mercury 7the atomic weight of mercury being halved71 may be formed by heating mercury in excess of chlorine1 or1 more economically1 by subliming a mixture of persulphate of mercury and chloride of sodium4 ,properties4--a very corrosive and poisonous salt1 usually sold in semi-transparent1 crystalline masses1 or in the state of powder4 ,soluble in #af parts of cold1 and in #c of hot water2 more abundantly so in alcohol1 and also in ether4 ,the solubility in water may be increased almost to any extent by the addition of free hydrochloric acid4 ,the protochloride of mercury is an insoluble white powder1 commonly known under the name of calomel4 ,milk4 ,the milk of herbivorous animals contains three principal constituents--fatty matter1 caseine1 and sugar2 in addition to these1 small quantities of the chloride of potassium1 and of phosphates of lime and magnesia1 are present4 ,the fatty matter is contained in small cells1 and forms the greater part of the cream which rises to the surface of the milk on standing4 ,hence skimmed milk is to be preferred for photographic use4 ,the second constituent1 caseine1 is an organic principle somewhat analogous to albumen in composition and properties4 ,its aqueous solution however does not1 like albumen1 coagulate on boiling1 unless an acid be present1 which probably removes a small portion of alkali with which the caseine was previously combined4 ,the substance termed rennet1 which is the dried stomach of the calf1 possesses the property of coagulating caseine1 but the exact mode of its action is unknown4 ,sherry wine is also employed to curdle milk2 but brandy and other spirituous liquids1 when free from acid and astringent matter1 have no effect4 ,in all these cases a proportion of the caseine usually remains in a soluble form in the whey2 but when the milk is coagulated by the addition of acids1 the quantity so left is very small1 and hence the use of the rennet is to be preferred1 since the presence of caseine facilitates the reduction of the sensitive silver salts4 ,caseine combines with oxide of silver in the same manner as albumen1 forming a white coagulum1 which becomes brick-red on exposure to light4 ,sugar of milk1 the third principal constituent1 differs from both cane and grape sugar2 it may be obtained by evaporating whey until crystallization begins to take place4 ,it is hard and gritty1 and only slightly sweet2 slowly soluble1 without forming a syrup1 in about two and a half parts of boiling1 and six of cold water4 ,it does not ferment and form alcohol on the addition of yeast1 like grape sugar1 but by the action of decomposing animal matter is converted into lactic acid4 ,when skimmed milk is exposed to the air for some hours it gradually becomes sour1 from lactic acid formed in this way2 and if then heated to ebullition1 the caseine coagulates very perfectly4 ,nitric ,acid4 ,symbol1 ,,no#e4 ,atomic weight1 #ed4 ,nitric acid1 or aqua-fortis1 is prepared by adding sulphuric acid to nitrate of potash1 and distilling the mixture in a retort4 ,sulphate of potash and free nitric acid are formed1 the latter of which1 being volatile1 distils over in combination with one atom of water previously united with sulphuric acid4 ,properties4--,anhydrous nitric acid is a solid substance1 white and crystalline1 but it cannot be prepared except by an expensive and complicated process4 ,the concentrated liquid nitric acid contains #a atom of water1 and has a sp4 gr4 of about #ae3 if perfectly pure it is colorless1 but usually it has a slight yellow tint1 from partial decomposition into peroxide of nitrogen3 it fumes strongly in the air4 ,the strength of commercial nitric acid is subject to much variation4 ,an acid of sp4 gr4 #adb1 containing about #d atoms of water1 is commonly met with4 ,if the specific gravity is much lower than this 7less than #acf71 it will scarcely be adapted for the preparation of peroxyline4 ,the yellow nitrous acid1 so called1 is a strong nitric acid partially saturated with the brown vapors of peroxide of nitrogen2 it has a high specific gravity1 but this is somewhat deceptive1 being caused in part by the presence of the peroxide4 ,on mixing with sulphuric acid the color disappears1 a compound being formed which has been termed a sulphate of nitrous acid4 ,chemical properties4--,nitric acid is a powerful oxidizing agent2 it dissolves all the common metals1 with the exception of gold and platinum4 ,animal substances1 such as the cuticle1 nails1 etc41 are tinged of a permanent yellow color1 and deeply corroded by a prolonged application4 ,nitric acid forms a numerous class of salts1 all of which are soluble in water4 ,hence its presence cannot be determined by any precipitating re-agent1 in the same manner as that of hydrochloric and sulphuric acid4 ,impurities of ,commercial ,nitric ,acid4--,these are principally chlorine and sulphuric acid2 also peroxide of nitrogen1 which tinges the acid yellow1 as already described4 ,chlorine is detected by diluting the acid with an equal bulk of distilled water1 and adding a few drops of nitrate of silver1--a milkiness1 which is chloride of silver in suspension1 indicates the presence of chlorine4 ,in testing for sulphuric acid1 dilute the nitric acid as before1 and drop in a single drop of solution of chloride of barium2 if sulphuric acid be present1 an insoluble precipitate of sulphate of baryta will be formed4 ,nitrous ,acid4 7,see ,silver1 ,nitrate of47 ,nitrate of ,potash4 ,symbol1 ,,ko ,,no#e4 ,atomic weight1 #ajb4 ,this salt1 also termed nitre or saltpetre1 is an abundant natural product1 found effloresced upon the soil in certain parts of the ,east ,indies4 ,it is also produced artificially in what are called nitre-beds4 ,nitrate of potash is an anhydrous salt1--it contains simply nitric acid and potash1 without any water of crystallization2 still1 in many cases1 a little water is retained mechanically between the interstices of the crystals1 and therefore it is better to dry before use4 ,this may be done by laying it in a state of fine powder upon blotting-paper1 close to a fire1 or upon a heated metallic plate4 ,nitrate of ,baryta4 ,symbol1 ,ba,o ,,no#e4 ,atomic weight1 #aca4 ,nitrate of baryta forms octahedral crystals1 which are anhydrous4 ,it is considerably less soluble than the chloride of barium1 requiring #ab parts of cold and #d of boiling water for solution4 ,it may be substituted for the nitrate of lead in the preparation of protonitrate of iron4 ,nitrate of ,lead4 ,symbol1 ,pb,o ,,no#e4 ,atomic weight1 #aff4 ,nitrate of lead is obtained by dissolving the metal1 or the oxide of lead1 in excess of nitric acid1 diluted with #b parts of water4 ,it crystallizes on evaporation in white anhydrous tetrahedra and octahedra1 which are hard1 and decrepitate on being heated2 they are soluble in #h parts of water at #fj4 ,nitrate of lead forms with sulphuric acid1 or soluble sulphates1 a white precipitate1 which is the insoluble sulphate of lead4 ,the ,iodide of lead is also very sparingly soluble in water4 ,nitrate of ,silver4 7,see ,silver1 ,nitrate of47 ,nitro-,hydrochloric ,acid4 ,symbol1 ,,no#d ,cl4 ,this liquid is the aqua-regia of the old alchemists4 ,it is produced by mixing nitric and hydrochloric acids3 the oxygen contained in the former combines with the hydrogen of the latter1 forming water and liberating chlorine1 thus3-- ,,no#e ,h,cl ,,no#d ,,ho ,cl4 ,the presence of free chlorine confers on the mixture the power of dissolving gold and platinum1 which neither of the two acids possesses separately4 ,in preparing aqua-regia it is usual to mix one part1 by measure1 of nitric acid with four of hydrochloric acid1 and to dilute with an equal bulk of water4 ,the application of a gentle heat assists the solution of the metal2 but if the temperature rises to the boiling point1 a violent effervescence and escape of chlorine takes place4 ,oxygen4 ,symbol1 ,o4 ,atomic weight1 #h4 ,oxygen gas may be obtained by heating nitrate of potash to redness1 but in this case it is contaminated with a portion of nitrogen4 ,the salt termed chlorate of potash 7the composition of which is closely analogous to that of the nitrate1 chlorine being substituted for nitrogen7 yields abundance of pure oxygen gas on the application of heat1 leaving behind chloride of potassium4 ,chemical ,properties4--,oxygen combines eagerly with many of the chemical elements1 forming oxides4 ,this chemical affinity however is not well seen when the elementary body is exposed to the action of oxygen in the gaseous form4 ,it is the nascent oxygen which acts most powerfully as an oxidizer4 ,by nascent oxygen is meant oxygen on the point of separation from other elementary atoms with which it was previously associated2 it may then be considered to be in the liquid form1 and hence it comes more perfectly into contact with the particles of the body to be oxidized4 ,illustrations of the superior chemical energy of nascent oxygen are numerous1 but none perhaps are more striking than the mild and gradual oxidizing influence exerted by atmospheric air1 as compared with the violent action of nitric acid and bodies of that class which contain oxygen loosely combined4 ,oxymel4 ,this syrup of honey and vinegar is prepared as follows3--,take of ,honey #a pound4 ,acid1 acetic1 fortiss4 7,beaufoy's acid7 #aa drachms4 ,water #ac drachms4 ,stand the pot containing the honey in boiling water until a scum rises to the surface1 which is to be removed two or three times4 ,then add the acetic acid and water1 and skim once more if required4 ,allow to cool1 and it will be fit for use4 ,potash4 ,symbol1 ,,ko ,,ho4 ,atomic weight1 #eg4 ,potash is obtained by separating the carbonic acid from carbonate of potash by means of caustic lime4 ,lime is a more feeble base than potash1 but the carbonate of lime1 being insoluble in water1 is at once formed on adding milk of lime to a solution of carbonate of potash4 ,properties4--,usually met with in the form of solid lumps1 or in cylindrical sticks1 which are formed by melting the potash and running it into a mould4 ,it always contain some atoms of water1 which cannot be driven off by the application of heat4 ,potash is soluble almost to any extent in water1 much heat being evolved4 ,the solution is powerfully alkaline and acts rapidly upon the skin2 it dissolves fatty and resinous bodies1 converting them into soaps2 ,solution of potash absorbs carbonic acid quickly from the air1 and should therefore be preserved in stoppered bottles2 the glass stoppers must be wiped occasionally1 in order to prevent them from becoming immovably fixed by the solvent action of the potash upon the silica of the glass4 ,the liquor potass of the ,london ,pharmacopoeia has a sp4 gr4 of #ajfc1 and contains about #e per cent2 of real potash4 ,it is usually contaminated with carbonate of potash1 which causes it to effervesce on the addition of acids2 also1 to a less extent1 with sulphate of potash1 chloride of potassium1 silica1 etc4 ,potash1 ,carbonate of4 ,symbol1 ,,ko ,,co#b4 ,atomic weight1 #gj4 ,the impure carbonate of potash1 termed pearlash1 is obtained from the ashes of wood and vegetable matter1 in the same manner as carbonate of soda is prepared from the ashes of seaweeds4 ,salts of potash and of soda appear essential to vegetation1 and are absorbed and approximated by the living tissues of the plant4 ,they exist in the vegetable structure combined with organic acids in the form of salts1 like the oxalate1 tartrate1 etc41 which when burned are converted into carbonates4 ,properties4--,the pearlash of commerce contains large and variable quantities of chloride of potassium1 sulphate of potash1 etc4 ,a purer carbonate is sold1 which is free from sulphates1 and with only a trace of chlorides4 ,carbonate of potash is a strongly alkaline salt1 deliquescent1 and soluble in twice its weight of cold water2 insoluble in alcohol1 and employed to deprive it of water4 ,pyrogallic ,acid4 ,symbol1 ,c#h;,h#d,o#d 7,stenhouse74 ,atomic weight4 #hd4 ,the term pyro prefixed to gallic acid implies that the new substance is obtained by the action of heat upon that body4 ,at a temperature of about #daj ,fahr41 gallic acid is decomposed1 and a white sublimate forms1 which condenses in lamellar ,crystals2 this is pyrogallic acid4 ,pyrogallic acid is very soluble in cold water1 and in alcohol and ether2 the solution decomposes and becomes brown by exposure to the air4 ,it gives an indigo blue color with protosulphate of iron1 which changes to dark green if any persulphate be present4 ,although termed an acid1 this substance is strictly neutral2 it does not redden litmus-paper1 and forms no salts4 ,the addition of potash or soda decomposes pyrogallic acid1 at the same time increasing the attraction for oxygen2 hence this mixture may conveniently be employed for absorbing the oxygen contained in atmospheric air4 ,the compounds of silver and gold are reduced by pyrogallic acid even more rapidly than by gallic acid1 the reducing agent absorbing the oxygen1 and becoming converted into carbonic acid and a brown matter insoluble in water4 ,commercial pyrogallic acid is often contaminated with empyreumatic oil1 and also with a black insoluble substance known as metagallic acid1 which is formed when the heat is raised above the proper temperature in the process of manufacture4 ,sel ,d'or4 7,see ,gold1 ,hyposulphite of47 ,silver4 ,symbol1 ,ag4 ,atomic ,weight1 #ajh4 ,this metal1 the luna or diana of the alchemists1 is found native in ,peru and ,mexico2 it occurs also in the form of sulphuret of silver4 ,when pure it has a sp4 gr4 of #aje1 and is very malleable and ductile2 melts at a bright red heat4 ,silver does not oxidize in the air1 but when exposed to an impure atmosphere containing traces of sulphuretted hydrogen1 it is slowly tarnished from formation of sulphuret of silver4 ,it dissolves in sulphuric acid1 but the best solvent is nitric acid4 ,the standard coin of the realm is an alloy of silver and copper1 containing about one-eleventh of the latter metal4 ,it may be converted into nitrate of silver1 sufficiently pure for photographic purposes1 by dissolving it in nitric acid and evaporating the solution to the crystallizing point3 or1 if the quantity be small1 the solution may be boiled down to complete dryness1 and the residue fused strongly2 which decomposes the nitrate of copper1 but leaves the greater portion of the silver salt unaffected4 7,n4 ,b4 ,nitrate of silver which has undergone fusion contains nitrite of silver1 and will require the addition of acetic acid if used for preparing the collodion sensitive film47 ,silver1 ,ammonio-,nitrate of4 ,crystallized nitrate of silver absorbs ammoniacal gas rapidly1 with production of heat sufficient to fuse the resulting compound1 which is white1 and consists of #ajj parts of the nitrate #bie of ammonia4 ,the compound however which photographers employ under the name of ammonio-nitrate of silver1 may be viewed more simply as a solution of the oxide of silver in ammonia1 without reference to the nitrate of ammonia necessarily produced in the reaction4 ,very strong ammonia1 in acting upon oxide of silver1 converts it into a black powder1 termed fulminating silver1 which possesses the most dangerous explosive properties4 ,its composition is uncertain4 ,in preparing ammonio-nitrate of silver by the common process1 the oxide first precipitated occasionally leaves a little black powder behind1 on re-solution2 this does not appear1 however1 according to the observations of the author1 to be fulminating silver4 ,in sensitizing salted paper by the ammonio-nitrate of silver1 free ammonia is necessarily formed4 ,thus3-- ,chloride of ammonium oxide of silver in ammonia chloride of silver ammonia water4 ,silver1 ,oxide of4 ,symbol1 ,ag,o4 ,atomic weight1 #aaf4 ,if a little potash or ammonia be added to solution of nitrate of silver1 a brown substance is formed1 which1 on standing1 collects at the bottom of the vessel4 ,this is oxide of silver1 displaced from its previous state of combination with nitric acid by the stronger oxide1 potash4 ,oxide of silver is soluble to a very minute extent in pure water1 the solution possessing an alkaline reaction to litmus2 it is easily dissolved by nitric or acetic acid1 forming a neutral nitrate or acetate2 also soluble in ammonia 7ammonio-nitrate of silver71 and in nitrate of ammonia hyposulphite of soda1 and cyanide of potassium4 ,long exposure to light converts it into a black substance1 which is probably a suboxide4 ,properties of the ,suboxide of ,silver4--,suboxide of silver bears the same relation to the ordinary brown protoxide of silver that subchloride bears to protochloride of silver4 ,it is a black powder1 which assumes the metallic lustre on rubbing1 and when treated with dilute acids is resolved into protoxide of silver which dissolves1 and metallic silver4 ,silver1 ,chloride of4 ,symbol1 ,ag,cl4 ,atomic weight1 #add4 ,preparation of ,chloride of ,silver by double decomposition4--,in order to illustrate this1 take a solution in water of chloride of sodium or common salt1 and mix it with a solution containing nitrate of silver2 immediately a dense1 curdy1 white precipitate falls1 which is the substance in question4 ,in this reaction the elements change places2 the chlorine leaves the sodium with which it was previously combined1 and crosses over to the silver2 the oxygen and nitric acid are released from the silver1 and unite with the sodium3 thus ,chloride of sodium nitrate of silver ,chloride of silver nitrate of soda4 ,this interchange of elements is termed by chemists double decomposition4 ,the essential requirements in two salts intended for the preparation of chloride of silver1 are simply that the first should contain chlorine1 the second silver1 and that both should be soluble in water2 hence the chloride of potassium or ammonium may be substituted for the chloride of sodium1 and the sulphate or acetate for the nitrate of silver4 ,in preparing chloride of silver by double decomposition1 the white clotty masses which first form must be washed repeatedly with water1 in order to free them from soluble nitrate of soda1 the other product of the change4 ,when this is done1 the salt is in a pure state1 and may be dried1 etc41 in the usual way4 ,properties of ,chloride of ,silver4--,chloride of silver differs in appearance from the nitrate of silver4 ,it is not met with in crystals1 but forms a soft white powder resembling common chalk or whiting4 ,it is tasteless and insoluble in water2 unaffected by boiling with the strongest nitric acid1 but sparingly dissolved by concentrated hydrochloric acid4 ,ammonia dissolves chloride of silver freely1 as do solutions of hyposulphite of soda and cyanide of potassium4 ,concentrated solutions of alkaline chlorides1 iodides1 and bromides are likewise solvents of chloride of silver1 but to a limited extent4 ,dry chloride of silver heated to redness fuses1 and concretes on cooling into a tough and semi-transparent substance1 which has been termed horn silver or luna cornea4 ,placed in contact with metallic zinc or iron acidified with dilute sulphuric acid1 chloride of silver is reduced to the metallic state1 the chlorine passing to the other metal under the decomposing influence of the galvanic current which is established4 ,preparation and properties of the ,subchloride of ,silver4--,if a plate of polished silver be dipped in solution of perchloride of iron1 or of bichloride of mercury1 a black stain is produced1 the iron or mercury salt losing a portion of chlorine1 which passes to the silver and converts it superficially into subchloride of silver4 ,this compound differs from the white chloride of silver in containing less chlorine and more of the metallic element2 the composition of the latter being represented by the formula ,ag,cl1 that of the former may perhaps be written as ,ag#b;,cl4 787 ,subchloride of silver is interesting to the photographer as corresponding in properties and composition with the ordinary chloride of silver blackened by light4 ,it is a pulverulent substance of a bluish-black color1 which is decomposed by ammonia1 hyposulphite of soda1 and cyanide of potassium1 into chloride of silver which dissolves1 and insoluble metallic silver4 ,silver1 ,bromide of4 ,symbol1 ,ag,br4 ,atomic weight1 #ahf4 ,this substance so closely resembles the corresponding salts containing1 chlorine and iodine1 that a short notice of it will suffice4 ,bromide of silver is prepared by exposing a silvered plate to the vapor of bromine1 or by adding solution of bromide of potassium to nitrate of silver4 ,it is an insoluble substance1 slightly yellow in color1 and distinguished from iodide of silver by dissolving in strong ammonia and in chloride of ammonium4 ,it is freely soluble in hyposulphite of soda and in cyanide of potassium4 ,silver1 ,citrate of4 7,see ,citric ,acid47 ,silver1 ,iodide of4 ,symbol1 ,ag,i4 ,atomic weight1 #bcd4 ,preparation and ,properties of ,iodide of ,silver4--,iodide of silver may be formed in an analogous manner to the chloride1 viz4 by the direct action of the vapor of iodine upon metallic silver1 or by double decomposition between solutions of iodide of potassium and nitrate of silver4 ,when prepared by the latter mode it forms an impalpable powder1 the color of which varies slightly with the manner of precipitation4 ,if the iodide of potassium be in excess1 the iodide of silver falls to the bottom of the vessel nearly white2 but with an excess of nitrate of silver it is of a straw-yellow tint4 ,this point may be noticed1 because the yellow salt is the one adapted for photographic use1 the other being insensible to the influence of light4 ,iodide of silver is tasteless and inodorous2 insoluble in water and in dilute nitric acid4 ,it is scarcely dissolved by ammonia1 which serves to distinguish it from the chloride of silver1 freely soluble in that liquid4 ,hyposulphite of soda and cyanide of potassium both dissolve iodide of silver2 it is also soluble in solutions of the alkaline bromides and iodides4 ,silver1 ,fluoride of4 ,symbol1 ,ag,f4 ,atomic weight1 #abg4 ,this compound differs from those just described in being soluble in water4 ,the dry salt fuses on being heated1 and is reduced by a higher temperature1 or by exposure to light4 ,silver1 ,sulphuret of4 ,symbol1 ,ag,s4 ,atomic weight1 #abd4 ,this compound is formed by the action of sulphur upon metallic silver1 or of sulphuretted hydrogen1 or hydrosulphate of ammonia1 upon the silver salts2 the decomposition of hyposulphite of silver also furnishes the black sulphuret4 ,sulphuret of silver is insoluble in water1 and nearly so in those substances which dissolve the chloride1 bromide1 and iodide1 such as ammonia1 hyposulphites1 cyanides1 etc42 but it dissolves in nitric acid1 being converted into soluble sulphate and nitrate of silver4 ,silver1 ,nitrate of4 ,symbol1 ,ag,o ,,no#e4 ,atomic weight1 #agj4 ,nitrate of silver is prepared by dissolving metallic silver in nitric acid4 ,nitric acid is a powerfully acid and corrosive substance1 containing two elementary bodies united in definite proportions4 ,these are nitrogen and oxygen2 the latter being present in greatest quantity4 ,nitric acid is a powerful solvent for the metallic bodies generally4 ,to illustrate its action in that particular1 as contrasted with other acids1 place pieces of silver foil in two test-tubes1 the one containing dilute sulphuric1 the other dilute nitric acid2 on the application of heat a violent action soon commences in the latter1 but the former is unaffected4 ,in order to understand the cause of the difference1 it must be borne in mind that when a metallic substance dissolves in an acid1 the nature of the solution is unlike that of an aqueous solution of salt or sugar4 ,if you take salt water1 and boil it down until the whole of the water has evaporated1 you obtain the salt again1 with properties the same as at first2 but if a similar experiment be made with a solution of silver in nitric acid1 the result is different3 in that case you do not get metallic silver on evaporation1 but silver combined with oxygen and nitric acid1 both of which are tightly retained1 being1 in fact1 in a state of chemical combination with the metal4 ,if we closely examine the effects produced by treating silver with nitric acid1 we find them to be of the following nature3--first1 a certain amount of oxygen is imparted to the metal1 so as to form an oxide1 and afterwards this oxide dissolves in another portion of the nitric acid1 producing nitrate of the oxide1 or1 as it is shortly termed1 nitrate of silver4 ,it is therefore the instability of nitric acid1 its proneness to part with oxygen1 which renders it superior to sulphuric acid in the experiment of dissolving silver4 ,nitric acid stands high in the list of oxidizing agents1 and it is important that the photographer should bear this fact in mind4 ,properties of ,nitrate of ,silver4--,in the preparation of nitrate of silver1 when the metal has dissolved1 the solution is boiled down in order to drive off the excess of nitric acid1 and set aside to crystallize4 ,the salt1 however1 as so obtained is still acid to test-paper1 and requires either recrystallization1 or a careful heating to about #cjj ,fahrenheit1 to render it perfectly neutral4 ,pure nitrate of silver occurs in the form of white crystalline plates1 which are very heavy and dissolve readily in an equal weight of cold water4 ,the solubility is much lessened by the presence of free nitric acid1 and in the concentrated nitric acid the crystals are almost insoluble4 ,boiling alcohol takes up about one-fourth part of its weight of the crystallized nitrate1 but deposits nearly the whole on cooling4 ,nitrate of silver has an intensely bitter and nauseous taste2 acting as a caustic1 and corroding the skin by a prolonged application4 ,its aqueous solution is perfectly neutral to test-paper4 ,heated in a crucible the salt melts1 and when poured into a mould and solidified1 forms the lunar caustic of commerce4 ,at a still higher temperature it is decomposed1 and bubbles of oxygen gas are evolved4 ,the melted mass1 cooled and dissolved in water1 leaves behind a black powder1 and yields a solution which is faintly alkaline to test-paper4 ,the alkalinity depends upon the presence of nitrite of silver associated with excess of oxide1 in the form probably of a basic or sub-nitrite of silver4,b ,footnote ,b3 ,nitrite of silver differs from the nitrate in containing less oxygen1 and is formed from it by the abstraction of two atoms of that element4 ,solution of nitrate of silver is decomposed by iron1 zinc1 copper1 mercury1 etc41 the nitric acid and oxygen passing to the other metal1 and metallic silver being precipitated4 ,silver1 ,nitrite of4 ,symbol1 ,ag,o ,,no#c4 ,atomic weight1 #aed4 ,nitrite of silver is a compound of nitrous acid1 or ,,no#c1 with oxide of silver4 ,it is formed by heating nitrate of silver1 so as to drive off a portion of its oxygen1 or more conveniently1 by mixing nitrate of silver and nitrate of potash in equal parts1 fusing strongly1 and dissolving in a small quantity of boiling water2 on cooling1 the nitrite crystallizes out1 and may be purified by pressing in blotting paper4 ,mr4 ,hadow describes an economical method of preparing nitrite of silver in quantity1 viz4 by heating #a part of starch in #h of nitric acid of #abe specific gravity1 and conducting the evolved gases into a solution of pure carbonate of soda until effervescence has ceased4 ,the nitrite of soda thus formed is afterwards added to nitrate of silver in the usual way4 ,properties4--,nitrite of silver is soluble in #abj parts of cold water2 easily soluble in boiling water1 and crystallizes1 on cooling1 in long slender needles4 ,it has a certain degree of affinity for oxygen1 and tends to pass into the condition of nitrate of silver2 but it is probable that its photographic properties depend more upon a decomposition of the salt and liberation of nitrous acid4 ,properties of ,nitrous ,acid4--,this substance possesses very feeble acid properties1 its salts being decomposed even by acetic acid4 ,it is an unstable body1 and splits up1 in contact with water1 into binoxide of nitrogen and nitric acid4 ,the peroxide of nitrogen1 ,,no#d1 is also decomposed by water and yields the same products4 ,silver1 ,acetate of4 ,symbol1 ,ag,o 7,c#d;,h#c,o#c74 ,atomic weight1 #afg4 ,this is a difficultly soluble salt1 deposited in lamellar crystals when an acetate is added to a strong solution of nitrate of silver4 ,if acetic acid be used in place of an acetate1 the acetate of silver does not fall so readily1 since the nitric acid which would then be liberated impedes the decomposition4 ,silver1 ,hyposulphite of4 ,symbol1 ,ag,o ,s#b,o#c 4 ,atomic weight1 #afd4 ,in order to understand1 more fully how decomposition of hyposulphite of silver may affect the process of fixing1 the peculiar properties of this salt should be studied4 ,with this view nitrate of silver and hyposulphite of soda may be mixed in equivalent proportions1 viz4 about twenty-one grains of the former salt to sixteen grains of the latter1 first dissolving each in separate vessels in half an ounce of distilled water4 ,these solutions are to be added to each other and well agitated2 immediately a dense deposit forms1 which is hyposulphite of silver4 ,at this point a curious series of changes commences4 ,the precipitate1 at first white and curdy1 soon alters in color3 it becomes canary-yellow1 then of a rich orange-yellow1 afterwards liver-color1 and finally black4 ,the rationale of these changes is explained to a certain extent by studying the composition of the hyposulphite of silver4 ,the formula for this substance is as follows3-- ,ag,o ,s#b,o#b1 ,but ,ag,o ,s#b,o#b plainly equals ,ag,s1 or sulphuret of silver1 and ,,so#c1 or sulphuric acid4 ,the acid reaction assumed by the supernatant liquid is due therefore to sulphuric acid1 and the black substance formed is sulphuret of silver4 ,the yellow and orange-yellow compounds are earlier stages of the decomposition1 but their exact nature is uncertain4 ,the instability of hyposulphite of silver is principally seen when1 it is in an isolated state3 the presence of an excess of hyposulphite of soda renders it more permanent1 by forming a double salt4 ,in fixing photographic prints this brown deposit of sulphuret of silver is very liable to form in the bath and upon the picture2 particularly so when the temperature is high4 ,to obviate it observe the following directions3--,it is especially in the reaction between nitrate of silver and hyposulphite of soda that the blackening is seen2 the chloride and other insoluble salts of silver being dissolved1 even to saturation1 without any decomposition of the hyposulphite first formed4 ,hence1 if the print be washed in water to remove the soluble nitrate1 a very much weaker fixing bath than usual may be employed4 ,this plan1 however1 involving a little additional trouble1 is1 on that account1 often objected to1 and1 when such is the case1 a concentrated solution of hyposulphite of soda must be used1 in order to dissolve off the white hyposulphite of silver before it begins to decompose4 ,when the proofs are taken at once from the printing frame and immersed in a dilute bath of hyposulphite 7one part of the salt to six or eight of water71 a shade of brown may often be observed to pass over the surface of the print1 and a large deposit of sulphuret of silver soon forms as the result of this decomposition4 ,on the other hand1 with a strong hyposulphite bath there is little or no discoloration and the black deposit is absent4 ,but even if1 by a preliminary removal of the nitrate of silver1 the danger of blackening be in a great measure obviated1 yet the print must not be taken out of the fixing bath too speedily1 or some appearance of brown patches1 visible by transmitted light1 may occur4 ,each atom of nitrate of silver requires three atoms of hyposulphite of soda to form the sweet and soluble double salt1 and hence1 if the action be not continued sufficiently long1 another compound will be formed almost tasteless and insoluble4 ,even immersion in a new bath of hyposulphite of soda does not fix the print when once the yellow stage of decomposition has been established4 ,this yellow salt is insoluble in hyposulphite of soda1 and consequently remains in the paper4 ,sugar of ,milk4 7,see ,milk47 ,sulphuretted ,hydrogen4 7,see ,hydrosulphuric ,acid47 ,sulphuric ,acid4 ,symbol1 ,,so#c4 ,atomic weight1 #dj4 ,sulphuric acid maybe formed by oxidizing sulphur with boiling nitric acid2 but this plan would be too expensive to be adopted on a large scale4 ,the commercial process for the manufacture of sulphuric acid is exceedingly ingenious and beautiful1 but it involves reactions which are too complicated to admit of a superficial explanation4 ,the sulphur is first burnt into gaseous sulphurous acid 7,,so#b71 and then1 by the agency of binoxide of nitrogen gas1 an additional atom of oxygen is imparted from the atmosphere1 so as to convert the ,,so#b into ,,so#c1 or sulphuric acid4 ,properties4--,anhydrous sulphuric acid is a white crystalline solid4 ,the strongest liquid acid always contains one atom of water1 which is closely associated with it1 and cannot be driven off by the application of heat4 ,this mono-hydrated sulphuric acid1 represented by the formula ,,ho ,,so#c1 is a dense fluid1 having a specific gravity of about #ahde2 boils at #fbj1 and distils without decomposition4 ,it is not volatile at common temperatures1 and therefore does not fume in the same manner as nitric or hydrochloric acid4 ,the concentrated acid may be cooled down even to zero without solidifying2 but a weaker compound1 containing twice the quantity of water1 and termed glacial sulphuric acid1 crystallizes at #dj ,fahr4 ,sulphuric acid is intensely acid and caustic1 but it does not destroy the skin or dissolve metals so readily as nitric acid4 ,it has an energetic attraction for water1 and when the two are mixed1 condensation ensues1 and much heat is evolved2 four parts of acid and one of water produce a temperature equal to that of boiling water4 ,mixed with aqueous nitric acid1 it forms the compound known as nitro-sulphuric acid4 ,sulphuric acid possesses intense chemical powers1 and displaces the greater number of ordinary acids from their salts4 ,it chars organic substances1 by removing the elements of water1 and converts alcohol into ether in a similar manner4 ,the strength of a given sample of sulphuric acid may generally be calculated from its specific gravity1 and a table is given by ,dr4 ,ure for that purpose4 ,impurities of ,commercial ,sulphuric ,acid4--,the liquid acid sold as oil of vitriol is tolerably constant in composition1 and seems to be as well adapted for photographic use as the pure sulphuric acid1 which is far more expensive4 ,the specific gravity should be about #ahcf at #fj4 ,if a drop1 evaporated upon platinum foil1 gives a fixed residue1 probably bisulphate of potash is present4 ,a milkiness1 on dilution1 indicates sulphate of lead4 ,test for ,sulphuric ,acid4--,if the presence of sulphuric acid1 or a soluble sulphate1 be suspected in any liquid1 it is tested for by adding a few drops of dilute solution of chloride of barium1 or nitrate of baryta4 ,a white precipitate1 insoluble in nitric acid1 indicates sulphuric acid4 ,if the liquid to be tested is very acid1 from nitric or hydrochloric acid1 it must be largely diluted before testing1 or a crystalline precipitate will form1 caused by the sparing solubility of the chloride of barium itself in acid solutions4 ,sulphurous ,acid4 ,symbol1 ,,so#b4 ,atomic weight1 #cb4 ,this is a gaseous compound1 formed by burning sulphur in atmospheric air or oxygen gas2 also by heating oil of vitriol in contact with metallic copper1 or with charcoal4 ,when an acid of any kind is added to hyposulphite of soda1 sulphurous acid is formed as a product of the decomposition of hyposulphurous acid1 but it afterwards disappears from the liquid by a secondary reaction1 resulting in the production of trithionate and tetrathionate of soda4 ,properties4--,sulphurous acid possesses a peculiar and suffocating odor1 familiar to all in the fumes of burning sulphur4 ,it is a feeble acid1 and escapes with effervescence1 like carbonic acid1 when its salts are treated with oil of vitriol4 ,it is soluble in water4 ,water4 ,symbol1 ,h#b,o4 ,atomic weight1 #i4 ,water is an oxide of hydrogen1 containing single atoms of each of the gases4 ,distilled water is water which has been vaporized and again condensed3 by this means it is freed from earthy and saline impurities1 which1 not being volatile1 are left in the body of the retort4 ,pure distilled water leaves no residue on evaporation1 and should remain perfectly clear on the addition of nitrate of silver1 even when exposed to the light2 it should also be neutral to test-paper4 ,the condensed water of steam-boilers sold as distilled water is apt to be contaminated with oily and empyreumatic matter1 which discolors nitrate of silver1 and is therefore injurious4 ,rain-water1 having undergone a natural process of distillation1 is free from inorganic salts1 but it usually contains a minute portion of ammonia1 which gives it an alkaline reaction to test-paper4 ,it is very good for photographic purposes if collected in clean vessels1 but when taken from a common rain-water tank should always be examined1 and if much organic matter be present1 tinging it of a brown color and imparting an unpleasant smell1 it must be rejected4 ,spring or river water1 commonly known as hard water1 usually contains sulphate of lime1 and carbonate of lime dissolved in carbonic acid3 also chloride of sodium in greater or less quantity4 ,on boiling the water1 the carbonic acid gas is evolved1 and the greater part of the carbonate of lime 7if any is present7 deposits1 forming an earthy incrustation on the boiler4 ,in testing water for sulphates and chlorides1 acidify a portion with a few drops of pure nitric acid1 free from chlorine 7if this is not at hand1 use pure acetic acid72 then divide it into two parts1 and add to the first a dilute solution of chloride of barium1 and to the second nitrate of silver1--a milkiness indicates the presence of sulphates in the first case or of chlorides in the second4 ,the photographic nitrate bath cannot be used as a test1 since the iodide of silver it contains is precipitated on dilution1 giving a milkiness which might be mistaken for chloride of silver4 ,common hard water can often be used for making a nitrate bath when nothing better is at hand4 ,the chlorides it contains are precipitated by the nitrate of silver1 leaving soluble nitrates in solution1 which are not injurious4 ,the carbonate of lime1 if any is present1 neutralizes free nitric acid1 rendering the bath alkaline in the same manner as carbonate of soda4 ,sulphate of lime1 usually present in well water1 is said to exercise a retarding action upon the sensitive silver salts1 but on this point the writer is unable to give certain information4 ,hard water is not often sufficiently pure for the developing fluids4 ,the chloride of sodium it contains decomposes the nitrate of silver upon the film1 and the image cannot be brought out perfectly4 ,the ,new ,river water1 however supplied to many parts of ,london1 is almost free from chlorides and answers very well4 ,in other cases a few drops of nitrate of silver solution may be added to separate the chlorine1 taking care not to use a large excess4 ,black ,varnish4 ,asphaltum1 dissolved in ,spirits or ,oil of ,turpentine4--,the asphaltum may be coarsely pulverized and put into a bottle containing the turpentine1 and in a few hours1 if it be occasionally shaken1 it will be dissolved and ready for use4 ,it should be of about the consistency of thick paste4 ,i use the above1 but will now give two more compositions1 for any who may wish to adopt them3 ,black ,japan4--,boil together a gallon of boiled linseed oil1 #h ounces of amber1 and #c ounces of asphaltum4 ,when sufficiently cool1 thin it with oil of turpentine4 ,brunswick ,black4--,melt #d lbs4 of asphaltum1 add #b lbs4 of hot boiled linseed oil1 and when sufficiently cool1 add a gallon of oil of turpentine4 ,the following is from ,humphrey's ,journal1 ,vol4 viii1 number #af4 ,black ,varnish4--,i generally purchase this from the dealer2 but ,i have made an article which answered the purpose well1 by dissolving pulverized asphaltum in spirits of turpentine4 ,any of the black varnishes can be improved by the addition of a little bees'-wax to it4 ,it is less liable to crack and gives an improved gloss4 ,before closing this chapter1 it has been thought advisable to remark1 that one of the most important departments of ,photography is the practice of its chemistry4 ,many of the annoying failures experienced by those who are just engaging in the practice of the art1 arise from the want of good and pure chemical agents1 and the most certain way to avoid this1 is to purchase them only from persons who thoroughly understand both their nature and mode of application4 ,as many who may read this work might wish to know the prices of the various articles employed in the practice of the processes given1 they can be informed by addressing the author1 who will furnish them with a printed ,price ,list4 ,,practical ,,details ,,of ,,the ,,positive ,,or ,,ambrotype ,,process4 ,,chapter ,,iv4 ,,lewis',s ,,patent ,,vices ,,for ,,holding ,,the ,,glass--,,cleaning ,,and ,,drying ,,the ,,glass--,,coating--,,exposure ,,in ,,the ,,camera--,,developing--,,fixing ,,or ,,brightening--,,backing ,,up1 ,c4 ,manipulations4 ,sidenote3 ,,manipulations4 ,under the head of manipulations ,i give the method ,i employ1 and avoid confusion by omitting all comments upon the thousand suggestions of others4 ,the glass is to have its sharp edges and corners removed1 by drawing a file once or twice over it4 ,the article used for holding the glass is called a vice4 ,this vice is firmly secured to a bench4 ,since the foregoing pages have been in type there has been introduced into market a new patent vice1 adopted both for glass and plate blocks4 ,i find it1 although a little more expensive1 an article better suited to the wants of the operator or amateur4 ,it is called ,lewis's ,patent ,glass ,vice4 ,clasp the glass firmly in the vice1 and pour or spurt upon it a little alcohol and rotten stone1 previously formed into a paste1 and then1 with a piece of cotton flannel1 the same as used in the daguerreotype1 rub the glass until it is perfectly cleansed from all foreign substances1 which will soon be known by experience4 ,the rotten stone paste should not be allowed to dry while rubbing1 as it is more liable to scratch the glass4 ,i use another small bottle containing clear alcohol1 which ,i spurt upon the glass1 to obviate the drying4 ,when the glass has been sufficiently cleaned1 it should1 while wet1 be put in a vessel of water for future rinsing4 ,clean1 as before1 as many plates of glass as may be required1 and when enough are ready1 rinse them off in the water1 and then in a quantity of clean water1 or a running current1 give them a second thorough rinsing1 and set them aside to drain4 ,a convenient method of doing this1 is to drive two nails horizontally into the wall or partition1 a sufficient distance apart 7say about #b-a_/b inches7 for the glass to rest on3 the upper corner of the glass should be placed against the wall1 and the extreme lower diagonal corner left hanging between the nails--which will probably be found the best position for draining yet suggested4 ,after drying1 they may be put into a box for safe and clean keeping4 ,particular caution is necessary to avoid handling the glass during the operation4 ,i never take the glass between my fingers1 so that they come in contact with both sides of it1 except at one particular corner1 as at ,figs4 ,a and ,b4 ,a quantity of glass prepared as above1 may be kept on hand for use two or three days1 and when wanted they should be again put into the vice,c and cleaned1 first with cotton flannel wet with alcohol1 and then with dry flannel2 and then1 at a temperature slightly above that of the surrounding atmosphere1 except in cases where the thermometer stands above #gj1 it is ready for the brush1,d which should be carefully applied to each surface1 to free it from all particles of dust1 and then it is ready for the film of collodion4 ,footnote ,c3 ,the vice should be thoroughly cleansed1 and no particles of rotten stone1 or other matter1 be allowed to come in contact with the glass1 as it might adhere to the edges and wash off into the silvering bath1 and ultimately cause specks4 ,always remember that cleanliness is an indispensable requisite in order to produce a good picture4 ,footnote ,d3 ,one of the most desirable articles ,i have found for this purpose is the wide 7#c inch7 flat camel's-hair brush often called a blender4 ,illustration3 ,fig4 ,a4 ,fig4 ,b4 ,the glass is held between the thumb and forefinger of the left hand by the corner #a1 ,fig4 ,a41 #c and #d towards and nearest the body1 and as nearly level as possible4 ,i find this the best position to hold the glass2 as1 in the case of the larger ones1 they can be rested on the end of the little finger1 which should be placed as near the edge as possible4 ,then1 from the collodion vial1 pour on the collodion1 commencing a little beyond the centre and towards #a1 continuing pouring in the same place until the collodion nearly reaches the thumb--the glass slightly inclined that way2 then let the glass incline towards #d1 and continue to pour towards #b4 ,as soon as enough has been put on to liberally flow the glass1 rapidly and steadily raise corner #a1 and hold it directly over #c1 where the excess will flow oil into the mouth of the vial1 which should be placed there to receive it4 ,in case of a speck of dust falling at the time of coating1 it can often be prevented from injuring the surface by changing the direction of the flowing collodion1 so as to stop it in some place where it will not be seen when the picture is finished4 ,now1 with the thumb and finger of the right hand1 ,i wipe off any drops or lines of collodion that may be found upon the outer edge or side of the glass1 being careful not to disturb that connected with the face4 ,when the coating has become sufficiently dry1 so that when ,i put my finger against it1 it does not break the film1 but only leaves a print1 ,i put it into the silvering bath see ,fig4 p4 #cd4 ,i generally try corners #b and #c4 ,the time1 from the first commencement of pouring on collodion to its being put into the bath1 should not exceed about half a minute1 at a temperature of #fj4 ,the finger test is the best ,i have found4 ,the glass is to be rested on a dipper see ,fig4 p4 #cd1 and placed steadily and firmly into the nitrate of silver bath--this in a dark room4 ,it should not be allowed to rest for an instant as it is entering the solution1 or it would cause a line4 ,the time for the glass to remain in the bath depends upon the age and amount of silver the bath contains2 for a new solution1 from two to three minutes will be sufficient to give the proper action4 ,if it be old1 three to five minutes will be better4 ,when it is properly coated1 it can be raised up and taken by the corner1 and allowed to drain for a few seconds1 and then should be placed in the tablet1 and is ready for the camera4 ,the time of exposure will depend upon the amount of light present4 ,if the bath is newly mixed1 and the collodion recently iodized1 it should produce a sufficiently strong impression by an exposure of about one-third of the time required for a daguerreotype4 ,if the collodion has been iodized some time1 and the bath is old1 about one-half of the time necessary to produce a daguerreian image will be required4 ,the plate should in no case be allowed to become dry from the time it is taken from the bath up to the time of pouring on the developer4 ,at a temperature of about #gj1 ,i have had the glass out of the bath ten minutes without drying4 ,after exposure1 the glass should be taken again into the dark room1 and removed from the tablet and held over a sink1 pail1 or basin and the developing solution poured on it as follows3 hold the glass between the thumb and finger of the left hand1 by the opposite end corner from that in coating with collodion1 i4 e41 #b1 and let #c and #d be from you4 ,sidenote3 ,,manipulations ,,of ,,the ,,positive ,,process4 ,commence pouring on the developing solution at the end by the thumb1 and let it flow quickly and evenly over the entire surface1 the first flooding washing off any excess of nitrate of silver there may be about the edges or corners of the glass 7if this silver is not washed off1 it flows over the edges and on the surface of the impression1 producing white wavy clouds of scum71 and then hold the glass as nearly level as possible1 it having upon its surface a thin covering of solution 7care should be observed not to pour the developing solution on the plate in one place1 as it would remove all the nitrate of silver and prevent the development of the image1 leaving only a dark or black spot where it is poured on74 ,put down the bottle containing the developing solution1 and take up a quart pitcher previously filled with water1 and as soon as the outline of the image can be plainly seen by the weak or subdued light of an oil or fluid lamp or candle1 pour the water over copiously and rapidly4 ,continue this until all the iron solution has been removed4 ,if this is not done1 the plate will be covered with blue scum on the application of the washing solution4 ,then the glass can be taken into a light room1 and the iodide of silver coating washed off with the cyanide solution1 and then rinsed with clear pure water1 and stood in a position to drain and dry4 ,i place a little blotting paper under them3 it aids in absorbing the water1 and facilitates the operation4 ,place the face of the glass against the wall1 in order to prevent dust from falling upon it4 ,i have often dried the coating by holding or standing the glass adjacent to a stove4 ,a steady heat is advisable1 as it leaves the surface in a more perfect state1 and free from any scum4 ,after the coating is perfectly dry1 it is ready for the preserving process4 ,it should be warmed evenly1 and when about milk warm1 ,humphrey's ,collodion ,gilding is poured on the image in precisely the same manner as the collodion4 ,in a few seconds the coating sets1 and after three-quarters of a minute1 if it has not become dry1 the blaze of a spirit lamp may be applied to the back and it will immediately become perfectly transparent1 and nearly as hard as the glass itself3 the effect is fully equal1 if not superior1 to that of chloride of gold in gilding the daguerreotype image4 ,the surface becomes brilliant and permanent4 ,the back of the glass can now be wiped and cleaned with paper or cloth1 and gently warmed1 and then with a common small brush one coat of black varnish can be applied4 ,this brush should be drawn from side to side across the glass1 and on the side opposite to that which has received the image4 ,this is in order not to make streaks in the coating of varnish1 but to have uniform lines across the entire length or breadth of the glass4 ,if the varnish is of the proper consistency1 it will flow into a smooth1 even coating4 ,after this first coating is dry1 apply a second in the same manner1 only in an opposite direction1 so as to cross the lines of the first1 uniting at right angles2 when this last coating is very nearly dry1 a piece of paper1 glazed black on one side1 and cut to the proper size1 can be put next the varnish2 it gives it a clean finish1 at the same time that it aids towards a dense blackening4 ,i sometimes apply the black varnish by flowing1 in the same manner as in putting on the collodion4 ,this picture is to be colored and put up in the same manner as the daguerreotype image1 with a mat and glass4 ,the last glass may be dispensed with by first using the collodion gilding1 and then upon its surface apply the black varnish1 as before4 ,in this case the image is seen through the same glass it is on1 and without being reversed3 in this case the mat goes on the outside of the glass4 ,when the image is seen through the glass upon which it is taken1 it cannot be colored with very great success1 as it cannot be seen through the reduced silver forming it4 ,this forms a more or less opaque surface2 but in point of economy the single glass is preferable4 ,yet ,i would not recommend such economy1 for ,i consider that a good impression ought to be well put up1 and the welfare of the art fully substantiates that consideration4 ,many ways have been devised for putting up pictures ,i have produced pleasing effects upon colored glasses3 for instance1 a picture on a light purple glass has a very pleasing effect2 also in some other colors4 ,i have also used patent leather for backing the image4 ,i have produced curious and interesting results by placing a piece of white paper1 or coloring white the back of the whites of the image1 and then blackening over or around this4 ,by this means the whites are preserved very clear4 ,positives for ,pins1 ,lockets1 etc4--,i employ mica for floating the collodion on1 as it can be as easily cut and fitted as the metallic plate in the daguerreotype2 and positives taken upon fine1 clear1 transparent mica1 are fully equal to those taken upon glass1 and yet they are ambrotypes4 ,mica is an article familiar to every one1 as being used in stoves1 gratings1 etc4 ,the method of using it1 is to take the impression on a thick piece1 and then split it off1 which can readily be done in the most perfect1 thin1 transparent plates2 it is equally as thin as tissue paper1 and can be cut as easily4 ,the thickness of the piece upon which the impression is taken is of no moment1 since it can be reduced at pleasure and is more easily handled while thick4 ,observations on the ,positive ,collodion ,process4 ,fogging4--,there are numerous causes which will produce fogging3 the principal ones will be mentioned4 ,one is the admission of light upon the collodion4 ,this maybe from a want of closeness of the dark room1 the tablet1,e the camera1 or by accidental exposure4 ,the method to locate the particular cause is to1 first1 when the glass is taken from the nitrate bath1 let it stand for sufficient time to drain1 then pour on the developer1 and if the coating assumes a mistiness1 or light-grey color1 the fault is in the dark room2 again1 if the plate1 after it has been treated with the developer and fixed1 is clear1 then also the fault is there4 ,now try the tablet in the same manner1 and if not there1 try the camera1 and the proper location will be found4 ,footnote ,e3 ,since the foregoing pages have been in type an entirely new feature in the line of apparatus has been introduced2 this is ,w4 ,w4 ,h4 ,lewis's ,patent ,plate-holder with solid glass corners4 ,these ,holders have every requisite for excluding the light from the sensitive surface2 they are accompanied with a shut off1 so that when the slide is drawn no light can reach the glass4 ,this1 in connection with the unequalled advantage of the solid corners1 makes them the most desirable article for the ,operator4 ,humphrey's ,journal1 in referring to these ,holders1 says3-- ,we are always glad to note every step which our mechanics make towards improvement on the apparatus used by our practical photographic operators1 and make the present announcement of one which has only to be known to be readily understood1 and to be seen to be appreciated4 ,a patent has recently been granted for making solid glass corners1 which are to be attached to plate-holders1 and form the most perfect article that has ever been introduced4 ,heretofore the operator has had the corners of his plate-holders made with separate pieces of glass1 cut so as to fit the corners of his frames2 these are only glued or grooved in1 and are constantly coming apart1 falling out1 and annoying in many ways2 for our part1 we never have considered them as fit for use in any manner4 ,we look upon the present improvement as destined to entirely supersede all the methods heretofore introduced4 ,in this case the collodionized or albumenized plate can come in contact with no other substance than a single piece of glass1 and consequently there is far less liability of accident from either the staining of the plate or breaking of the holder4 ,the rapid favor this improvement has gained already shows its great advantage over all other methods heretofore employed4 ,decomposition by exposure to light or by long keeping1 even in the dark4 ,the author conceives that it is possible for organic matter alone to produce1 after a time1 a partial decomposition of solution of nitrate of silver1 sufficient to prevent it from being employed chemically neutral1 but probably not much interfering with its properties in other respects4 ,use of rain water or of water containing carbonate of silver being perfectly neutral and from nitric acid4 ,this difficulty is not a theoretical one only1 but has actually been experienced4 ,rain water usually contains ammonia1 and has a faint alkaline reaction4 ,pump water often abounds with carbonate of lime1 much of which1 but not the whole1 is deposited on boiling4 ,to remove the alkaline condition1 add acetic acid1 one drop to half a pint of the solution4 ,partial decomposition of the bath1 by contact with metallic iron1 with hyposulphite of soda1 or with any developing agent1 even in small quantity4 ,also by the use of accelerators1 which injure the bath by degrees1 and eventually prevent its employment in an accurately neutral state4 ,vapor of ammonia1 or hydrosulphate of ammonia1 escaping into the developing room4 ,spots4--,one principal cause of spots is dust4 ,the operating room should be kept as free from this as possible1 and instead of its being dusted1 it should be wiped with a damp cloth4 ,specks or flakes of iodide of silver are often found in the nitrate bath4 ,these sometimes occur by an ever-iodized collodion1 and sometimes by collodion falling off while being silvered4 ,when this occurs1 the nitrate of silver solution should be filtered4 ,a new sponge or a tuft of cotton is a good article to filter nitrate of silver solution through4 ,a small particle of light finding its way upon the plate1 will produce a spot4 ,another and very frequent cause is1 putting the slide of the tablet down rapidly1 causing it to spatter upon the plate the solution which has drained off from it4 ,this paper will be opaque when viewed by reflected light1 and dark when viewed by transmitted light4 ,occasionally a sort of transparent spot will appear3 this may be traced to a want of sensibility of the iodide of silver4 ,large transparent spots frequently appear by the operator's pouring the developing solution upon one place1 and washing off the small quantity of nitrate of silver necessary to develope the image4 ,this will be easily detected1 and can be obviated by flooding the most of the surface of the glass with a steady stream of the developer4 ,stains and ,lines4--,if the glass be allowed to rest for an instant with one portion of its surface in the silvering solution and the other out of it1 it would cause a streak across2 hence the necessity of totally immersing it with one firm1 steady motion removing the glass before it has been thoroughly wetted1 and the ether and alcohol allowed a uniform action over the entire surface4 ,a plate should not be disturbed in the bath until it has been in a full minute at least4 ,irregular ,lines are often caused by using the developing solution too strong1 or by not pouring it evenly over the plate at once4 ,should it be allowed to rest in its progress1 if but for an instant1 it will leave its line4 ,sometimes spangles of metallic silver appear3 these are caused by the presence of too much nitric acid in the developer for the proportion of iodide in the film and the strength of the bath4 ,there are other phases connected with the practice of the positive process1 which it would be almost impossible to commit to paper1 and cannot be so explained as to be perfectly comprehended by the new experimenter4 ,it is absolutely necessary for all to observe every little point noticed in the foregoing pages1 and at the same time exercise some good judgment1 and no one need hesitate through fear of not being successful4 ,,practical ,,details ,,of ,,the ,,negative ,,process4 ,,chapter ,v4 ,,negative ,,process--,,soluble ,,cotton--,,plain ,,collodion--,,developing ,,solution--,,re-,,developing ,,solution--,,fixing ,,the ,,image--,,finishing ,,the ,,image--,,nitrate ,,of ,,silver ,,bath4 ,negative ,process4 ,the manipulations and chemicals employed in the production of the negative collodion pictures are very similar to those already given for operating by the positive process2 frequent reference will therefore necessarily be made to portions of that process1 as described in the preceding pages1 and only such parts will be given here1 as do not correspond with the foregoing4 ,it is thought advisable to omit in this chapter every reference that does not have a desired tendency to aid the operator in the plain straightforward order of manipulation4 ,the negative process is fast becoming popular and needs the attention of all who desire to keep pace with the experiments in the art4 ,since the first edition of this work it has been my pleasure to see many fine photographic specimens produced by the following process1 and no one need fail1 if he will carefully adhere to the details given4 ,there perhaps may be circumstances making it advisable for some to have but one nitrate of silver solution for both positive and negative collodion pictures3 for such1 a process will be given in the following pages1 which has recently appeared in ,humphrey's ,journal1 and is called1 after its author1 the ,helio ,process1 this is well adapted for most purposes4 ,soluble ,cotton4 ,the method for preparing this has been given in page #da4 ,it is prepared in the same manner for both positives and negatives4 ,plain ,collodion4 ,the preparation of plain collodion employed is the same as that described at page #ec4 ,developing ,solution for ,negatives4 ,rain or distilled water #f ounces4 ,protosulphate of iron #cjj grains4 ,acetic acid #b ounces4 ,a little alcohol may be added to make it flow more evenly over the plate--say #a oz4 ,this solution can be kept in a pint bottle1 and should have a funnel devoted solely to the purpose of filtering it4 ,one of the most convenient dishes for receiving this solution1 when poured over the plate1 is a bowl with a lip to it1 as it can be readily poured back into the funnel4 ,the mode of employing this developer is the same as that for positives1 described at page #acc4 ,it may be used an indefinite number of times1 but should be kept clean2 it soon assumes a red color4 ,re-developing ,solution4 ,this solution is for the purpose of giving increased intensity to the negative1 but as its use in the hands of beginners is attended with some difficulty1 ,i would not recommend the operator to try it until he has had considerable experience in the developing process1 or he will undoubtedly spoil his proofs4 ,its use requires promptness of action and quick observation4 ,the following is the formula for its preparation3 ,water #d ounces4 ,protosulphite of iron #djj grains4 ,put this into a bottle1 and when the crystals are dissolved1 it is ready for use4 ,it should be kept filtered1 and can be used only once4 ,now in another bottle put ,water #d ounces4 ,nitrate of silver #dh grains4 ,remarks4--,the impression is to be well washed after the developing solution has been poured off1 and then the re-developing solution 7that portion containing the protosulphate of iron7 can be poured on--the plate being held perfectly level3 the surface is completely covered2 the water containing the nitrate of silver should then be poured rapidly on1 to mix with the iron1 when the surface of the impression will instantly commence to blacken2 and if the action be allowed to continue for a lengthened period1 say one minute1 the impression will be ruined4 ,it is a matter worthy of notice1 that there is no perceptible action when the iron solution is poured over the glass2 but the action is very energetic the instant the nitrate of silver solution comes in contact with the iron salt and the silver4 ,as soon as any change can be observed1 after the re-developer has been poured over the plate1 it should be quickly and copiously washed off with clean water1 and then it is ready for the fixing process4 ,i would dissuade novices in the art from practising with the re-developing solution1 until they have first thoroughly mastered the entire process of taking negatives4 ,the developing solution is the only one used by operators generally1 and will1 with proper care1 produce satisfactory results4 ,fixing the ,image4 ,water #h ounces4 ,hyposulphite of soda #d ounces4 ,remarks4--,this is nearly a saturated solution4 ,the glass can be put in a dish and the solution poured over1 or held in the hand1 in the same way as the plate in the daguerreotype process4 ,it can readily be seen when a sufficient action has been attained1 as the unaltered bromo-iodide of silver will be dissolved1 leaving only the reduced surface holding the image4 ,this action should not be continued too long1 as it affects the intensity of the picture1 injuring it for printing4 ,the glass should be well washed by pouring over it clean water1 and then it can be stood away to dry1 in a nearly perpendicular position1 on clean blotting paper1 or otherwise1 as is most convenient2 when thoroughly dry1 it is ready for the finishing4 ,finishing the ,image4 ,this is done with the same material1 and in the same manner1 as that given for positives--page #acd4 ,remarks4--,the glass negatives1 when not wanted for use1 should be carefully put aside in a box1 and kept free from dust and dampness3 by so doing1 it is believed that they will remain good for any length of time4 ,nitrate of ,silver ,bath4 ,this solution differs only from the positive bath1 by omitting the nitric acid3 in all other respects it is precisely the same1 and is prepared by the same formula1 as given at page #fd4 ,this is called the neutral bath1 and is best adapted to the negative process4 ,the nitrate of silver employed in its preparation should be perfectly free from excess of nitric acid1 otherwise the whole solution will be slightly acid4 ,if it should not be convenient to obtain nitrate of silver without this objection1 the acid may be neutralized by putting into the solution a small quantity of common washing soda-- say #a grain to each #ajj grains of nitrate of silver--previously dissolved in about half an ounce of water4 ,this may be put in at the same time that the iodide of potassium is1 and it would save one filtration4 ,in twenty samples of nitrate of silver that ,i have tried the above quantity of soda has been found sufficient2 if1 however1 the white precipitate first formed is re-dissolved on shaking the mixture1 free nitric acid is present1 and more of the soda may be added4 ,this bath will improve by age1 and be less liable to fog after having been in constant use for one or two weeks4 ,operators who have the means1 and design following the art professionally1 will find it to their advantage to make from two to three times the quantity of solution they require for immediate use3 by this means they will be enabled to replenish their stock1 which may be used up or otherwise lost4 ,,practical ,,details ,,of ,,the ,,printing ,,process4 ,,chapter ,,vi4 ,,printing ,,process--,,salting ,,paper--,,silvering ,,paper--,,printing ,,the ,,positive--,,fixing ,,and ,,coloring ,,bath--,,mounting ,,the ,,positive4 ,the ,printing ,process4 ,sidenote3 ,,manipulations ,,of ,,the ,,printing ,,process4 ,there is probably no department of the photographic art where can be found an equal amount of variety1 as regards chemicals1 manipulations1 etc4 ,the course adopted in the commencement1 of giving only one process for the operator to work by--and that a good one--will be strictly adhered to in this place4 ,i have produced as good positives on paper by the following plan1 as ,i have ever seen4 ,should the reader wish more extensive acquaintance with the printing processes1 he is referred to ,humphrey's ,journal4 ,salting ,paper4 ,water #a quart4 ,muriate of ammonia #fe grains4 ,the water is put into a flat1 gutta-percha1 glass1 or earthen dish1 and the muriate of ammonia is put into it1 and stirred until it is dissolved and is well mixed with the water2 then proceed as follows3 we will suppose we have a gutta-percha dish sufficiently large to take in a sheet of paper #h by #aj inches1 and about #a-a_/b or #b inches deep3 take hold of two corners of the paper with the thumb and finger of each hand1 and then draw the paper through the solution1 by passing it from one end of the dish to the other1 so that it will be wetted on both sides2 then turning it over in the same manner1 draw it back1 so that its surface will be thoroughly moistened1 but it is not necessary to saturate the paper4 ,now the paper is ready for drying1 which may be done by hanging it on the edge of a shelf by means of little tack nails put through it at the same corners by which it was held in passing through the salting solution4 ,in order to prevent streaks1 from forming upon the paper1 it is better to hang it in such a manner that it cannot touch the shelf1 except at the corners3 say the sheet is eight inches wide1 and the tacks 7which are put through the corners7 to be only five or six inches apart1 this will give the proper bend outwards1 preventing its contact with the shelf4 ,this entire operation can be performed in daylight1 or otherwise as suits the convenience of the operator4 ,this paper1 when dry1 should be laid between the folds of blotting paper 7filtering paper will answer71 and may be kept for any length of time1 and is ready for the silvering process4 ,silvering ,paper4 ,in silvering paper1 ,i employ the ammonio-nitrate1 which is prepared as follows3-- ,water #b-a_/d ounces4 ,nitrate of silver #ge grains4 ,dissolve 7in a #d-ounce vial7 the nitrate of silver in the water1 and then pour one-fourth of the solution into an ounce graduate or any convenient vessel3 this keep for farther use in preventing the presence of an excess of ammonia4 ,now1 into the bottle containing the three-fourths put about #d drops of aqua-ammonia2 shake well and a brown precipitate will be given4 ,continue adding the ammonia1 drop by drop1 and shake after each addition1 until the brown precipitate is re-dissolved and the solution is clear2 then pour back into the bottle the one-fourth taken out at first3 this will leave the solution slightly turbid1 and when so1 there is no excess of ammonia which would be objectionable4 ,it may now be filtered through filtering paper1 and it 7the clear liquid7 is ready for use4 ,this should be kept in the dark1 as it decomposes rapidly when exposed to light4 ,the method of silvering the paper with ammonio-nitrate of silver1 is as follows3 take a tuft of clean cotton1 roll it into a ball-shape1 then wet it by holding it against the mouth of the bottle containing the ammonio-nitrate1 and when well wet1 apply it to the paper 7which should be placed flat on a clean board7 by gently rubbing it over the surface1 care being taken not to roughen it4 ,if the solution has not been filtered for some time1 it would be advisable to pour a little on the centre of the paper1 and then distribute it over the surface by means of the cotton1 which is held in the fingers3 by this last method any sediment which may be in the bottom of the bottle is prevented from getting upon the paper1 and causing spots4 ,i have used a brush for the purpose of distributing the solution1 by which plan there is less liability of getting it on the fingers and staining them4 ,care must be taken to cover the entire surface of the paper1 or there will be light streaks1 occasioned by the absence of the silvering solution4 ,this want of silver will appear on the paper in light parts1 as seen in the accompanying cut3 ,illustration3 ,fig4 #cf4 ,after the paper has been perfectly coated1 or washed with the silvering solution1 it should be placed in a perpendicular position to dry4 ,i usually tack the paper on a board of the requisite size1 and then stand it on one edge until it has drained and dried4 ,as soon as dry1 it is ready for use4 ,this paper will not keep more than twelve hours1 therefore the operator should silver in the morning the quantity required for the day4 ,it is imperatively necessary that the silvered paper be kept in the dark4 ,it is extremely sensitive to light1 and a very brief exposure of the prepared sheet would render it unfit for use4 ,printing the ,positive4 ,the several kinds of apparatus used for holding the negative and the sensitive paper together1 have already been given on page #cf1 ,figs4 #ca1 #cb1 #cc4 ,the paper having been salted and silvered1 as just described1 should be placed on the pad of the printing frame or glasses1 with its sensitive surface up1 and then the negative placed directly upon and in contact with it2 then it is to be fastened together1 when it will be ready for exposure to the direct rays of the sun4 ,from #aj to #dj seconds will be found enough to give a sufficiently intense print4 ,the paper first changes to a slate color1 and then to a brown or copper color t when of a dark slate color is about the proper time to take it out and immerse in the toning bath4 ,fixing and ,coloring ,bath4 ,i have employed the proportions given by ,mr4 ,hardwich in his ,photographic ,chemistry1 page #bji--;,humphrey's ,american edition4 ,solution of chloride of gold1 a quantity equivalent to #d grains4 ,nitrate of silver #cj ,hyposulphite of soda #b ounces4 ,water #h ,dissolve the hyposulphite of soda in four ounces of the water1 the chloride of gold in three ounces1 the nitrate of silver in the remaining ounce2 then pour the diluted chloride by degrees into the hyposulphite1 stirring meanwhile with a glass rod2 and afterwards the nitrate of silver in the same way4 ,this order of mixing the solution is to be strictly observed2 if it were reversed1 the hyposulphite of soda being added to the chloride of gold1 the result would be the reduction of metallic gold4 ,the difference depends upon the fact that the hyposulphite of gold which is formed is an exceedingly unstable substance1 and cannot exist in contact with unaltered chloride of gold4 ,it is necessary that it should be dissolved by hyposulphite of soda immediately on its formation1 and so rendered more permanent by conversion into a double salt of soda and gold4 ,the time of coloration depends much upon the quantity of gold present1 and may in some cases be extended to many hours4 ,the results of a few experiments1 performed roughly1 appeared to indicate that the activity of this bath is less affected by depression of temperature than those prepared with tetrathionate4 ,certainly the injurious effects of prolonged immersion are not so evident as with the first two formul3 the purity of the whites remains unaltered for many hours if the bath is new1 but with an old bath there is a tendency to yellowness1 which is probably caused by the presence of sulphuretted hydrogen4 ,fresh chloride of gold must be added from time to time1 as it appears to be required4 ,after the impression has remained in the toning bath a sufficient length of time1 it should be placed in a dish or sink of clean water1 which should be changed several times--floating for at least #ab hours2 then it may be taken out and hung up to dry4 ,touching4--,the coloring of a photograph forms no part of my process3 this is a matter to be given into the hands of an artist1 and when it bears the finishing touch of his skill1 it is no longer a photograph1 but an oil or watercolor painting2 all the delicate workings of nature having been lost or hidden under the colors4 ,a photograph may often be touched to advantage4 ,if1 as is frequently the case1 there be little white spots on the face of the paper1 they may be readily covered by the application of a little ,india ink1 with the point of a wet pencil or fine small brush4 ,mounting of ,positives4 ,this1 though a small matter in itself1 is worthy of great attention4 ,the durability of the proof depends much upon the purity of the paste used in causing its adhesion to the ,bristol board4 ,i have employed the following composition with the most eminent success3-- ,gum arabic #b ounces ,gum tragacanth #a-a_/b ,isinglass #a-a_/b ,sugar #a_/b ,water #c pints ,these ingredients should all be dissolved1 and then boiled down to the proper consistency1 by means of a gentle heat4 ,i will give another composition1 which will serve a good purpose1 and keep for a long time3-- ,water #h ounces4 ,one table spoonful of wheat flour ,powdered alum #dj grains4 ,powdered resin ,brown sugar #a ounce4 ,bichloride of mercury #bj grains4 ,this last composition may be more convenient for operators1 and it will answer the purpose well4 ,it is thought by some to be the best and most durable paste yet prepared for the purpose4 ,,facts ,,worth ,,mentioning4 ,sidenote3 ,,facts ,,worth ,,knowing4 ,the ,poisonous ,effects of cyanide of potassium upon sores1 may be obviated by immediately applying some of the positive developing solution1 described at page #fb4 ,by this means much annoyance may be avoided to persons afflicted with chapped or sore hands4 ,bending ,glass ,rods or tubes can be easily done by subjecting them to the blaze of a spirit lamp--the same as that used for gilding the daguerreotype4 ,first hold the rod just above the blaze1 then gradually allow it to descend into it1 imparting to the rod a rotatory motion with the finger and thumb3 this will soon cause a softening of the glass1 when it may be bent to any desired shape4 ,if the ends are to be bent to form hooks1 another small piece of glass1 or any warm metal1 may be placed upon the end1 in the blaze of the lamp1 and as soon as thoroughly softened1 it can be pressed or bent to form the hook4 ,by filing around a glass tube or rod1 it may be easily and safely broken at the desired point1 by giving it a sudden jerk between both hands1 holding it close to the encircled part4 ,cementing ,glass may be readily accomplished by placing the two ends together in the blaze of the lamp1 and holding them there until they attain a sufficient degree of heat to slightly fuse3 when cool1 the ends will be found perfectly united4 ,the ,background best adapted to positives is unbleached muslin1 such1 as is sold for sheeting1 and can be found in almost any dry goods' store3 it should be from two to three yards wide4 ,a clouded appearance is given to the background by merely marking it with charcoal1 forming streaks or waves resembling clouds4 ,these come out black1 or dark1 in the positive1 and give a variegated appearance4 ,the roughness of the marking does not matter1 since the background is generally a little out of the focus of the lenses4 ,trees and other designs may be represented in this matter4 ,positive ,collodion ,pictures may be whitened by the use of bichloride of mercury1 thirty grains to one ounce of water4 ,after the picture has been developed1 fixed and washed1 by the process given in the preceding pages1 the solution of bichloride of mercury may be poured over the surface of the image3 it almost immediately presents a series of interesting changes in color4 ,the surface at first blackens but for a few minutes1 when it begins to get lighter1 and gradually brightens to a pure white1 inclining to a blue4 ,it should then be thoroughly washed and dried1 as usual4 ,instantaneous ,pictures may be taken by employing the iodide of iron in the collodion4 ,the best method with which ,i am acquainted1 is to have a saturated solution of iodide of iron in alcohol1 and drop one or two drops into an ounce of the collodion 7which has been previously iodized7 used in taking positives4 ,this can be used at once1 as soon as mixed4 ,no more of this collodion should be prepared than is wanted for immediate use1 as it will keep good for only a few hours4 ,the saturated solution of iodide of iron can be kept on hand ready for use at all times4 ,there should be an excess of the iodide in the alcohol4 ,the same accelerating effect is produced with the negative collodion prepared in this way4 ,plain ,collodion may be iodized as soon as dissolved3 this will save time in settling4 ,it is a fact that some cotton is more readily dissolved when the bromo-iodizing is present3 but by the addition of this1 ,i have often taken up considerable quantities of the gummy sediment remaining in the bottom of bottles4 ,prepared ,glass may be preserved clean and free from dust by keeping in boxes such as those used for keeping daguerreotype plates4 ,by taking out every other partition between the grooves1 the glass can be readily put in4 ,collodion ,vials and ,bottles1 after having collodion in them once1 should be rinsed with alcohol and ether 7in the same proportions as employed for dissolving the cotton71 before using them a second time for that purpose4 ,penuriousness in this respect would be bad policy4 ,coating ,large ,glasses4--,a convenient method of doing this is represented in the following illustration3 ,illustration ,the glass is held by one corner1 #b2 the other corner1 #d1 is rested on a table or bench1 and the collodion poured on1 so that the excess may be poured off at #a4 ,black ,stains upon the hands1 caused by nitrate of silver1 may be removed by moistening them and rubbing with a lump of cyanuret of potassium4 ,this salt is poisonous1 if used to a great extent ,see page #aci4 ,another safer1 but more expensive plan1 however1 is to take a saturated solution of iodide of potassium in water1 and then wash with nitric acid diluted with two parts water4 ,stains upon ,white ,linen can be removed by washing with a saturated solution of iodide of potassium containing a little iodine2 then wash with water1 and soak in a saturated solution of hyposulphite of soda until the yellow iodide of silver is dissolved4 ,the hands should always be washed after fixing a positive or negative picture1 before again touching a glass to be coated1 or the dipper2 this precaution is necessary1 lest any of the iron salt1 or the hyposulphite1 should get into the silvering solution and spoil it4 ,in taking ,collodion ,pictures1 it is always advisable for the sitter to be arranged before the glass is taken from the bath3 this will save time and there will be less liability of the collodion drying4 ,a ,good ,negative may be known by its possessing the following characteristics3--,by transmitted light the figure is bright1 and appears to stand out from the glass2 the dark shadows are clear1 without any misty deposit of metallic silver2 the high lights black almost to complete opacity4 ,a ,glass ,coated with ,collodion1 if kept too long before immersion in the bath1 will not be equally sensitive over its surface2 the parts most dry being the least sensitive4 ,glass ,pans1 for ,scales1 can be procured by every one at trifling expense3 ,take a watch crystal1 and place in the common metal pan2 balance this with lead1 or any weight3 this can easily be kept clean1 and is the most advisable for weighing all deliquescent salts1 and chemicals employed in the collodion process4 ,caution4--,persons engaged in making collodion1 and using ether and alcohol1 must bear in mind that these chemicals are very inflammable2 hence extreme caution is necessary to avoid exposing them to the flame of a lamp or candle4 ,i have known of several serious accidents1 of recent date1 all of which were caused by the imprudence of the experimenter in the particular above mentioned4 ,wipe the ,plate-holder every time before the glass is put into it3 this will prevent spots1 which might otherwise occur from the presence of nitrate of silver solution which drained from the plate previously used4 ,these spots are of an opaque yellowish tinge1 and in shape resemble the stain which would be occasioned by a splash of water4 ,glass jar ,positives4--,a good white or light-green glass will answer for the collodion coating4 ,glass which contains air-spots can be used1 if it be placed in such a manner as to let the light of the image come over them1 as the spots cannot be seen through the opaque surface4 ,only the best white glass should be used for covering the picture4 ,some operators use the convex glass1 which is very clear1 and answers the purpose4 ,the ,nitrate of ,silver ,bath should be kept covered1 except when in use4 ,if a ,glass be ,immersed too soon1 streaks and waves will be occasioned4 ,these will be seen at the end of the plate which is least dry3 the coating is also more liable to peel off4 ,it should be borne in mind1 however1 that the peeling of collodion is not always attributable to this cause4 ,diffused ,light in the ,developing ,room4--,in proportion as the sensitiveness of the plates increases1 greater care must be exercised in thoroughly excluding all rays of white light4 ,with opalescent films1 neutral1 this cause of fogging is more common than any other4 ,tn the case of a portrait1 if the features have an unnaturally black and gloomy appearance1 the dark portions of the drapery1 c41 being invisible1 the picture has been underexposed in the camera4 ,,chapter ,,vii4 ,,helio ,,process4,f ,footnote ,f3 ,it has been thought advisable to publish in this work the ,helio ,process1 and ,i do so just as it appeared in ,humphrey's ,journal4--,s4 ,d4 ,h4 ,an ,entire ,process for ,producing ,collodion ,positives and ,negatives with one ,bath1 and in much less time than by any other known ,process4--,by ,helio4--,photographic ,patents4 ,boston1 ,oct41 #ahef4 ,s4 ,d4 ,humphrey4 ,sir1--,as ,humphrey's ,journal is the only truly progressive and independent ,photographic publication in ,america1 ,i feel it the duty of every one to aid its ,editor in furthering the interest of the amateur and practitioner of the art2 and1 suiting the action to the word1 ,i present the following ,process as being worthy of confidence1 and having1 in my hands1 proved eminently satisfactory4 ,i am surprised to see that ,operators and men respectably connected with the practice of the ,art should so far fall beneath the station of true artists as to advertise to catch each other1 or the verdant ones1 by offering this or that little improvement all printed complete for five dollars4 ,as an amateur1 and having the good of the science ,i love at heart1 ,i now contribute my mite for the benefit of all interested2 and1 following the glorious example of ,g4 ,b4 ,c4 7who ,i hope we shall soon hear from again17 in your last1 ,i say--,god speed6 ,i shall endeavor to be as minute and concise as possible1 so as to enable any one to adopt and successfully use my processes4 ,preparation of ,soluble ,cotton4--,i put into a ,wedgewood mortar1 twelve ounces1 by weight1 of dry and finely pulverized nitrate of potash 7,i use ,dupont's refined71 and add to it twelve ounces1 by measure1 of good commercial sulphuric acid2 ,i mix these well together by the use of a glass rod and pestle1 so that it forms a paste2 ,i then add1 in small quantities at a time1 about #cbe grains of good coarse cotton 7this is according to your process71 and knead the mass well for from three to five minutes2 and then cover the mortar with a piece of glass1 and let it stand for twenty or thirty minutes1 by which time it will have been sufficiently acted upon4 ,then the cotton is to be plunged into a quantity of clean water and thoroughly washed in a number of changes of water1 so that when it is squeezed between the folds of blue litmus-paper it will not redden it2 this indicates that the acid has been washed out2 ,i then place the cotton in a clean strong towel and wring out all the water ,i can1 then put it into alcohol1 then wring it again1 and adopt your plan of not letting it become thoroughly dry4 ,the cotton being now ready for use1 ,i dissolve it in the following mixture1 in a bottle of proper size3-- ,sulphuric ether #aj ounces4 ,alcohol1 #ie per cent4 #e ounces4 ,soluble cotton1 enough to make it about as thick as cream4 ,the above should be well shaken1 and then allowed to stand for one or two days to settle4 ,this constitutes my ,plain ,collodion1 and should be poured off into another bottle1 leaving the sediment behind4 ,iodizing4--,for this purpose ,i employ the following preparation3-- ,a4--,iodide of ,silver4--,dissolve fifty grains of nitrate of silver1 crystals1 in two ounces of pure water1 and forty grains of iodide of ammonium in two ounces of pure water2 then pour the two together1 shaking the mixture well2 let it settle1 which it will do in a few minutes2 then pour off the water carefully1 leaving behind all the yellow iodide of silver2 pour again a fresh quantity of water over the precipitate1 and continue this washing for at least six changes of water2 then drain off the water as close as possible and pour on two ounces of alcohol1 which1 when drained off1 will leave the powder sufficiently clean for the purpose4 ,b4--,i now dissolve forty grains of bromide of ammonium and one hundred grains of iodide of ammonium in two ounces of #ie per cent1 alcohol1 and then add the iodide of silver 7preparation ,a71 and shake the whole well together1 giving a saturated solution4 ,this is to be filtered through cotton or paper1 when it will be ready for use4 ,c4--,to sixteen ounces of ,plain ,collodion add from eight to twelve drops of tincture of iodine 7#ej grains of dry iodine dissolved in half an oz4 of alcohol7 and #ad grains or drops of fluoride of ammonium2 shake the mixture well2 then add all of the solution ,b2 shake it again and thoroughly2 after this has stood for twenty-four hours it can be used1 but will be found better after it has been prepared one week4 ,nitrate of ,silver ,solution4 ,pure rain or distilled water #fd ounces4 ,nitrate of silver 7in crystals7 #d-a_/d ounces4 ,clean pure white sugar #ge grains4 ,six grains of iodide of ammonium dissolved in half a drachm of alcohol4 ,the above1 thoroughly mixed and allowed to stand for a few hours1 should be filtered through a new clean sponge1 asbestos1 or ,swedish filtering paper1 and then a few drops of nitric acid1 chemically pure1 should be added1 just enough to redden blue litmus-paper2 then it is ready for use1 and will improve by age4 ,developing ,solution4--,this formula has proved very satisfactory in my hands1 and ,i hope will be equally so with all who give it a trial3-- ,water #a pint4 ,boracic acid #c_/d ounce4 ,protosulphate of iron #c_/d ounce4 ,pulverized nitre #a_/b ounce ,three drops of oil of cinnamon dissolved in two ounces of alcohol4 ,dissolve and filter1 and it is ready for use4 ,it is better to make this developer fresh every other day4 ,dissolving off the ,iodide of ,silver4--,water1 about half a pint2 cyanide of potassium1 enough to clear the impression in about thirty seconds--say a quarter of an ounce4 ,fixing the ,impression4--,i use the article well known to every good photographer as ,humphrey's ,collodion ,gilding1 and it serves the purpose better than anything that ,i ,i know of4 ,black ,varnish4--,i generally purchase this from the dealer2 but ,i have made an article which answered the purpose well1 by dissolving pulverized asphaltum in spirits of turpentine4 ,any of the black varnishes can be improved by the addition of a little bees'-wax to it4 ,it is less liable to crack and gives an improved gloss4 ,negative and ,printing ,processes4--,being myself an amateur1 and desiring to study economy and convenience1 my attention has been given to the test of numerous plans for avoiding the necessity of two baths and silvering solutions and ,i feel confident that the amateur will find the following1 in connection with the foregoing ,positive ,process1 the best adapted to his wants4 ,the same bath and solution is used for the negative as for the positive process2 and the time of exposure in the camera should be prolonged a few seconds4 ,i have produced beautiful negatives1 in-doors1 in four seconds1 and1 out-doors1 instantaneously4 ,the manipulation1 bath1 and developing solution are precisely the same as those used in the positive process4 ,fixing the ,negative4--,place the following mixture in a well-stoppered bottle3 ,pure ,water #f ounces4 ,aqua-ammonia1 concentrated #a ounce4 ,this solution should be poured on the negative and allowed to remain for about twenty seconds4 ,it should be borne in mind1 that the developing solution 7same as for positives7 should be well washed off the glass before the fixing solution is poured over2 after it has remained on the glass for the time given 7#bj seconds71 the negative can be washed with clean water and dried2 it is then ready for printing4 ,the iodide of silver is not1 as in other processes1 dissolved off1 but remains on the glass4 ,it sometimes happens that the negative is not sufficiently intense2 this result can be obtained by pouring over the plate the following solution1 which should remain for about three-fourths of a minute3 ,water #h ounces4 ,nitrate of silver #bh grains4 ,alcohol #a ounce4 ,loaf sugar #a_/c ounce ,after this solution is used1 ,i pour over the impression the developing solution1 and then wash well with water4 ,this re-developing may be repeated two or three times1 and almost any desired intensity obtained4 ,printing ,process--,salting the ,paper4--,boil the following mixture in an earthen vessel until it becomes transparent3-- ,distilled water #ab ounces4 ,muriate of ammonia #bdj grains4 ,arrowroot #aab grains4 ,after this has been sufficiently boiled1 it should be strained through clean linen or cotton cloth 7free from soap or other substances71 and1 when cool1 it is ready for coating the paper1 which is done by dipping a new clean sponge into it and rubbing it over one side of the paper1 giving it a uniform coating2 but as it is not desirable to have too much on the paper1 it should be rubbed with a clean sponge until nearly dry2 it can then be hung up by the corner until thoroughly dry1 when it can be put into a portfolio and kept for exciting for use4 ,silvering ,solution4--,this solution may be prepared in the light1 but must be used in a dark room3-- ,distilled water #a pint4 ,nitrate of silver #c-c_/d ounces4 ,dissolve and pour into an earthen or gutta-percha dish4 ,take the paper 7cut to the proper size7 and float it on this solution for about three minutes2 care must be observed that there are no air-bubbles between the solution and the paper1 for this would cause spots4 ,it now can be hung up to dry1 and as soon as dry it may be used4 ,let me here repeat1 that this operation must be conducted in a dark room4 ,fixing and ,toning ,bath4--,i find that a better effect is produced if the positive be a little over-printed before being acted upon by the following mixture3-- ,distilled water #h ounces4 ,chloride of sodium #bdj grains4 ,this solution should be put into a flat dish and the print placed on it1 face down1 for from one and a-half to three minutes1 when it should be taken off and put into the following solution1 and allowed to remain there from three quarters of an hour to two hours3-- ,distilled water #ah ounces4 ,hyposulphite of soda #c ounces4 ,nitrate of silver #fj grains4 ,the following method should be observed in preparing this last mixture1 viz43--dissolve the three ounces of hyposulphite of soda in sixteen ounces of the water and the sixty grains of nitrate of silver in the remaining two ounces2 then pour the nitrate of silver solution into that containing the hyposulphite of soda1 stirring the mixture continually until all is well mixed4 ,after the print has remained in the toning solution for the specified time1 it should be taken out and well washed in several changes of clean water1 and dried and mounted in any of the usual ways4 ,with a few general remarks ,i will close this1 perhaps1 too long communication4 ,it should be a point in the practice of every one who desires success in any process1 to maintain a strict observance to cleanliness2 this is one point in which most persons fail1 and it cannot be too strongly impressed upon the minds of manipulators4 ,it should be understood that the foregoing process is complete in itself1 and is not to be confounded with any other method4 ,the collodion is adapted for the nitrate of silver bath1 and the bath for the collodion2 and no one should use other preparations of collodion and silvering solution1 except they do so with the full expectation that it will be at the loss of either or both of the preparations employed4 ,allow me1 through the columns of your invaluable ,journal1 to say to those who may read the foregoing process1 that if they find 7as ,i have7 my process to prove profitable to them1 ,i shall consider myself amply repaid if they will1 through the same medium1 contribute to our stock of information by giving an account of their experiments4 ,i feel quite confident that some of the amateurs1 with whose reputation ,i am already acquainted1 and of whose private works in photography ,america has cause to feel proud1--could furnish interesting1 useful and valuable information upon this subject4 ,such men1 for instance1 as ,g4 ,b4 ,c1 of ,md4 7who has already made a good beginning71 ,g4 ,w4 ,d41 of the same place1 and ,mr4 ,g4 ,g41 of ,pa4 ,friends and co-laborers1 shall we hear from you8 ,i pause for a reply6 ,i look with interest upon every stroke of the pen from your able correspondent ,g4 ,m41 of ,washington1 whose specimens of photographic engraving you recently had the kindness to show me4 ,i assure you1 it did not a little astonish me to witness the surprising truthfulness with which the details were presented4 ,helio4 ,,correspondence ,,between ,,the ,u4 ,s4 ,,commissioner ,,of ,,patents ,,and ,,james ,a4 ,,cutting1 ,,relative ,,to ,,his ,,applications ,,for ,,letters ,,patent4 ,united ,states ,patent ,office1 ,april #ag1 #ahed4 ,sir3 ,your application for letters patent for an alleged improvement in making photographic pictures1 having been submitted to the proper examiner1 is rejected4 ,as the use of alcohol to absorb water in hasty desiccation is understood to be commonly practical in most chemical laboratories1 no reference is thought necessary for the rejection of the first claim4 ,secondly1 the mixture of alcohol and ether in unlimited proportions to dissolve gun cotton for photographic purposes1 is common4 ,see ,gaudin's ,process1 ,humphrey's ,daguerreian ,journal1 vol4 #d1 p4 #bbi4 ,thirdly1 collodion with bromide basis1 is not new4 ,see ,general ,remarks on ,collodion1 by ,gaudin1 ,photographic ,art ,journal1 #ast ,series1 vol4 #f1 p4 #cdh4 ,the two articles above referred to are translated from the ,french1 and contain also1 it is believed1 sufficient to show that the subject of the fourth claim has been anticipated1 rendering further reference unnecessary4 ,respectfully yours1 c41 ,s4 ,f4 ,shugert1 ,acting ,commissioner4 ,j4 ,a4 ,cutting 7care of ,c4 ,g4 ,page71 ,washington1 ,d4 ,c4 99 99 99 99 99 ,jane #ag1 #ahed4 ,sir3 ,in regard to the use of bromide bases with collodion1 ,i am prepared to show that ,i had it in successful use in the month of ,april1 #ahec2 and if the circumstances require legal proof of the same1 it will be furnished1 though at some expense of time and money to me2 and as the question is only between the public and myself1 ,i trust the office will see fit to grant me a patent for the same4 ,james ,a4 ,cutting4 ,hon4 ,chas4 ,mason1 ,commissioner of ,patents4 99 99 99 99 99 ,united ,states ,patent ,office1 ,april #ai1 #ahed4 ,sir3 ,in your letter of the #agth1 you say that1 if necessary1 proof can be given that you had in successful use1 in the month of ,april1 #ahec1 collodion prepared with a bromide oasis4 ,on referring to the ,journal of the ,photographic ,society1 of ,london1 ,no4 #f 7,june1 #ahec71 page #gj1 you will see that ,sir ,john ,herschel used bromide for the same purpose previous to the year #ahdj4 ,ammonia1 in various combinations1 has long been in use for the preparation of sensitive collodions4 ,see ,report of the ,british ,association1 #ahej1 p4 #aej1 ,journal of the ,photographic ,society ,no4 #i1 #ahec1 p4 #aaf4 ,f4 ,m4 ,lyndes' process and compositions show that he has used iodine1 bromide1 and chloride of ammonium2 and ,count de ,montegon1 in the same journal1 ,no4 #b1 ,april1 #ahec2 page #bd1 for his fifth composition of collodion1 used liquid ammonia4 ,these are all regarded as equivalents for your compositions covered by the fourth claim2 if1 however1 there is a difference1 you are at liberty to show in what it consists2 and the examination is accordingly postponed to await your action4 ,yours1 c41 ,c4 ,mason1 ,commissioner4 ,j4 ,a4 ,cutting 7care of ,c4 ,g4 ,page71 ,washington1 ,d4 ,c4 99 99 99 99 99 ,washington1 ,june #ba1 #ahed4 ,sir3 ,in reply to your communications of the #aith instant1 and ,april #agth1 #ahed1 ,i propose to modify my claims as follows1 to wit3 ,after the first clause of the claim1 nineteenth line1 ending with the words set forth1 add as follows3 ,i do not claim the use of alcohol as a desiccating agent1 but limit my claim to its special use and purpose1 as herein stated4 ,erase the fourth clause of the claim1 commencing on the twenty-sixth line1 and ending with the words set forth on the thirtieth line4 ,in reply to the objection raised by the office that bromide was used in #ahdj1 ,i have to say that ,i was fully aware of the employment of bromide in various ways for photographic purposes1 and that ,i have also1 in common with photographers1 known the extreme difficulty of using bromide1 and that notwithstanding the sensitiveness imparted by bromide to other compounds1 it has been almost universally discarded by practical photographers4 ,the discovery of collodion as a vehicle for sensitive materials is of recent date1 and there seems to have been a backwardness on the part of photographers to attempt bromide bases with collodion1 and so far1 whatever trials have been made subsequent to my discovery1 it is evident that they have been attended with the results of misty pictures4 ,to whatever my success may be due1 ,i maintain that ,i have been the first to use a bromide base with collodion--and with that only do ,i claim it--and the results in my pictures show with what success4 ,respectfully1 ,james ,a4 ,cutting1 ,by ,att'y1 ,chas4 ,g4 ,page4 ,hon4 ,chas4 ,mason1 ,commissioner of ,patents4 99 99 99 99 99 ,united ,states ,patent ,office1 ,june #ba1 #ahed4 ,sir3 ,your specification of an improvement in composition for producing photographic pictures is herewith returned for a slight amendment1 which is1 to omit the reference to specimens which do not accompany the patent1 and to correct an error in the oath as noted on the margin4 ,yours1 c41 ,c4 ,mason1 ,commissioner4 ,james ,a4 ,cutting1 #adb ,hanover st42 ,boston1 ,mass4 99 99 99 99 99 ,united ,states ,patent ,office1 ,june #bb1 #ahed4 ,sir3 ,by reading a paper by ,mr4 ,w4 ,crookes in the ,journal of the ,photographic ,society1 ,london1 ,no4 #g1 p4 #hf1 on the employment of bromine in collodion1 it is believed you will be satisfied that the date there given on which he used bromized collodion is prior to your claim to having used it2 he refers to p4 #gb1 ,no1 #f1 published in ,june1 #ahec1 for experiments made with bromized collodion1 which paper is dated ,june #b;d1 #ahec4 ,mr4 ,isaac ,rehn1 of ,philadelphia1 has testified to having seen you make use of a bromide base1 viz41 bromide of potassium and collodion1 about the #ast of ,july1 #ahec1 or about one month after the date of ,mr4 ,crookes' paper in ,england4 ,the specification is accordingly returned1 that you may cancel the fourth claim1 and amend the papers to suit4 ,yours1 c41 ,c4 ,mason1 ,commissioner4 ,mr4 ,j4 ,a4 ,cutting1 7care of ,c4 ,g4 ,page71 ,washington1 ,d4 ,c4 99 99 99 99 99 ,,patent ,,for ,,the ,,use ,,of ,,camphor ,,in ,,combination ,,with ,,iodized ,,collodion4 ,the schedule referred to in the ,letters ,patent1 and making part of the same4 ,to whom it may concern3 ,be it known1 that ,i1 ,james ,a4 ,cutting1 of the ,city of ,boston1 ,county of ,suffolk1 and ,state of ,massachusetts1 have invented a new and useful improvement in positive photographic pictures on glass1 and ,i do hereby declare the following to be an exact description thereof3 ,the nature of my invention consists in the use of gum camphor1 in addition to the existing materials in the preparation of collodion for positive photographic pictures on glass4 ,to enable others skilled in the art to make and use my invention1 ,i will proceed to describe the process as follows3 ,having prepared the collodion in the usual manner1 ,i take a pint bottle1 in which ,i introduce twelve ounces of collodion1 to which ,i add one drachm of iodide of potassium1 dissolved in alcohol4 ,i then shake the mixture thoroughly1 and add thereto eighteen grains of refined gum camphor1 shaking the mixture again1 until the whole is combined1 then allow it to settle1 when it is lit for use4 ,the advantages of my improvement consist in the increased vigor of the delineations of the half-tones of positive pictures on glass1 giving greater depth and rotundity thereto1 which render this combination exceedingly useful for microscopic pictures1 as well as the ordinary purposes of portraiture4 ,t would have it understood that the combination of camphor with iodide of potassium and collodion1 as above specified1 is adapted solely to the production of positive pictures on glass and not to the production of negative pictures on glass1 from which positive pictures on paper may be printed1 as a sufficient degree of opacity is not thus afforded for that purpose4 ,what ,i claim as my invention1 and desire to secure by ,letters ,patent1 is the use of camphor1 in combination with iodized collodion1 as set forth in the specification4 ,james ,a4 ,cutting4 ,samuel ,grubb1 ,witnesses4 ,i4 ,rehn4 ,dated1 ,july #dth1 #ahed4 99 99 99 99 99 ,,patent ,,for ,,the ,,use ,,of ,,balsam ,,for ,,sealing ,,photographic ,,pictures ,,on ,,glass4 ,the schedule referred to in ,letters ,patent and making part of the same4 ,to whom it may concern3 ,be it known that ,i1 ,james ,a4 ,cutting1 of ,boston1 in the ,county of ,suffolk and ,state of ,massachusetts1 have invented new and useful improvements in photographic pictures on glass1 and ,i do hereby declare the following to be an exact description thereof3 ,the nature of my improvement consists in the application of a coating of balsam of fir to the side of the glass on which the picture is made1 over which coating ,i place another glass of equal size with the one on which the picture is4 ,to enable others skilled in the art to make and use my invention1 ,i will proceed to describe the process as follows3 ,after thoroughly cleaning a glass plate of the same size as that on which the picture to be secured is made1 and moving all dust from the picture1 ,i hold the glass containing the picture in a horizontal position with the pictured side uppermost1 then apply the balsam in a line along one edge of the glass and placing one edge of the second glass in close contact with the first1 containing the balsam1 press them gradually together towards the opposite edge1 causing the balsam to flow by a gentle pressure towards the opposite edge1 in this manner excluding all air from between the glasses2 then by an even pressure exclude the superabundant balsam4 ,the advantages of my improvements are1 that by a mechanical combination of the balsam with the picture it is greatly increased in strength and beauty1 by an additional brilliancy and the exhibition of the most minute delineations2 and by the application of the second glass in combination with the balsam1 the picture is hermetically sealed and rendered entirely permanent1 by being secured from the influence of both air and moisture1 and also from injury by dust or other extraneous matter1 or acid vapors1 or any violence less than what could occasion the fracture of the plate glass4 ,i am aware of the previous use of balsam for the cementing of lenses and the securing of microscopic objects1 and other like purposes1 and do not therefore extend my claim to any of these uses2 but ,what ,i claim as my invention1 and desire to secure by ,letters ,patent1 is the combination of balsam with photographic pictures on glass1 and with additional glass by which they2 with the balsam1 are hermetically sealed1 as described in the specifications2 and for the purposes therein set forth1 and for no other4 ,james ,a4 ,cutting4 ,issac ,rehn1 ,witnesses4 ,samuel ,grubb4 ,dated ,july #aath1 #ahed4 99 99 99 99 99 ,,patent ,,for ,,displacing ,,water ,,from ,,soluble ,,cotton ,,by ,,the ,,use ,,of ,,alcohol2 ,,also1 ,,for ,,the ,,use ,,of ,,bromide ,,of ,,potassium ,,in ,,combination ,,with ,,collodion4 ,the schedule referred to in these ,letters ,patent1 and making part of the same4 ,to all to whom these presents shall come3 ,be it known that ,i1 ,james ,a4 ,cutting1 of ,boston1 in the ,county of ,suffolk and ,state of ,massachusetts1 have invented certain improvements in making photographic pictures1 and that the following is a full1 clear and exact description of the principle or character which distinguishes them from all other things before known1 and of the usual manner of making1 modifying1 and using the same4 ,my improvements relate to that class of photographic pictures in which the pictures are obtained upon a prepared film of glass or other substance4 ,the film which ,i employ is collodion1 and in order to insure success1 the collodion must be prepared after my own process1 as follows3 ,take #c ounces 7,troy7 of pure dry nitrate potassa1 and pulverize in a clean glass mortar2 add to this #b-a_/b ounces1 fluid measure1 of pure sulphuric acid1 and stir the mixture with a glass rod2 immerse in this liquid1 #hj grains of clean1 dry cotton1 and knead the mass of cotton in the liquid for about ,ave minutes2 remove the cotton and quickly wash it1 till every trace of acid is gone1 and it must then be dried quickly--for ,i have discovered that the more rapidly the cotton is dried1 the more sensitive the collodion2 and ,i have found the best effects produced by displacing the water from the cotton by strong alcohol4 ,to prepare the collodion1 take #aj ounces concentrated sulphuric ether1 #fj ,baum1 and mix this with #f ounces of #ie per cent4 alcohol4 ,to this mixture add the prepared cotton1 in quantity sufficient to make a collodion as thick as it can1 and yet at the same time flow evenly over the surface of glass4 ,let it settle clear1 and decant the solution4 ,in order to excite this collodion1 take a deep #a ounce vial--introduce #b-a_/b grains of bromide of potassium1 and add water1 drop by drop1 to make a saturated solution4 ,in this solution dissolve #b-a_/b grains of iodide of potassium1 then add #a ounce of collodion1 and shake well4 ,let it settle clear and decant for use4 ,the solution must be decanted every day4 ,in order to make the most sensitive collodion1 ,i dissolve the bromide and iodide of potassium and the collodion,g in a saturated solution of carbonate of ammonia in water4 ,in using this collodion1 pour it upon a clean glass plate to form a film in the usual way1 and as soon as the collodion has set1 and before it becomes dry1 immerse the plate in a bath of nitrate of silver1 made with #cj grains of nitrate of silver1 #b grains of iodide of silver1 and #a ounce water4 ,take the plate directly from the bath to the camera1 and after sufficient exposure1 the plate is taken to a dark room to develope the impression with the following solution3 ',take pyrogallic acid1 #d grains2 acetic acid1 ,no4 #h1 #a ounce2 dissolve and filter4 ,for use1 take of this liquid #a-a_/b drachms1 diluted with #f-a_/b drachms of water1 and when the impression is sufficiently developed1 pour off the liquid1 and immerse the plate in a solution of the hyposulphite of soda1 #d ounces to the pint of water4 ,wash the plate with pure water1 and dry it in the usual way4 ,footnote ,g3 ,this is a mistake3 the collodion is not to be dissolved in the carbonate of ammonia in water1 but only the bromide and iodide of potassium4 ,i called ,mr4 ,cutting's attention to this1 and he said ,i was correct4--,s4 ,d4 ,h4 ,the advantages of the above process are1 the brief time required to produce an impression1 and the sharpness of the pictures4 ,portraits can be taken with as much facility as with the ,daguerreotype1 and the pictures are sharp and of excellent tone4 ,the impression thus obtained is negative1 and the positive picture is produced in the usual way4 ,i denominate this the mezzographic process4 ,what ,i claim as my improvements in the process of obtaining photographic pictures1 are-- ,first4 ,displacing the water from the cotton1 for this purpose1 with strong alcohol1 as set forth4 ,i do not claim the use of alcohol as a desiccating agent1 but limit my claim to its special use and purpose1 as herein stated4 ,second4 ,the employment of bromide of potassium in combination with collodion4 ,james ,a4 ,cutting4 ,t4 ,campbell1 ,witnesses4 ,samuel ,grubb4 ,dated ,july #aath1 #ahed4 99 99 99 99 99 ,,patent ,,for ,,the ,,use ,,of ,,japanned ,,surfaces ,,previously ,,prepared ,,upon ,,iron ,,or ,,other ,,metallic ,,or ,,mineral ,,sheets ,,or ,,plates ,,in ,,the ,,collodion ,,process4 ,to all whom it may concern3 ,be it known that ,i1 ,hamilton ,l4 ,smith1 of ,gambier1 in the ,county of ,knox1 and ,state of ,ohio1 have invented certain new and useful improvements in ,photographic ,pictures1 and ,i do hereby declare the following to be a full1 clear1 and exact description of the same1 and of the manner of making and using my invention or discovery4 ,the nature of my invention or discovery relates to the taking of positive pictures by the photographic process1 upon a black japanned surface prepared upon iron or any other metallic plates or sheets1 and consists in the use of collodion1 and a solution of a salt of silver1 and an ordinary camera4 ,to enable others skilled in the art to make and use my invention4 ,i will proceed to describe the manner of preparing and applying it which ,i have found to answer well in practice2 not confining myself1 however1 to the special process or processes herein described1 so long as the characteristics of the invention remain the same4 ,i first take metallic sheets1 preferring for the purpose iron1 as this metal is the only one1 except the precious metals1 which is without action on the silver salts generally used1 as also the other chemicals2 but other metallic or mineral sheets may be used1 and ,i do not1 therefore1 confine myself specially to any particular metal4 ,upon each of the sheets is prepared a black japanned or varnished surface1 such as is used by tinners or japanners for coating metallic and other surfaces4 ,the japan or varnish may be made and applied as follows3--,take one quart of raw linseed oil2 add to this two ounces of asphaltum and sufficient umber1 or lamp black1 to give the desired shade4 ,boil these ingredients until a portion dropped on a cool surface will remain in a round spot without flowing away4 ,it is then thick enough to use4 ,if it should be too thick1 it can readily be thinned with spirits of turpentine4 ,apply the japan to the sheets or plates with a brush1 and after allowing it to stand a short time1 until the marks of the brush disappear1 place the sheets or plates in a drying oven and submit them to heat until the surface will bear the finger to be drawn over it without bringing off the japan2 it may1 if found necessary1 be coated again and treated in a similar way1 and finally polished with rotten-stone and oil1 or other polishing material4 ,other ingredients may be used in making the japan1 such as mastic1 lac or copal varnish1 and other shades of coloring matter may be used4 ,by collodion ,i mean any solution of gun-cotton or pyroxyline2 and by a solution of salt of silver1 ,i mean any of the salts thereof which can be used in photography for obtaining positive impressions by a camera4 ,a japanned surface may be prepared on glass1 or on leather and other fibrous materials4 ,or glass may be made black by means of coloring matter introduced or embodied with the glass1 so as to be in instead of on the glass4 ,but foreseeing the difficulty of embracing all these applications in one application1 ,i do not desire to have them so considered2 but reserve the right to hereafter apply for such application of my general principle as ,i may deem essential1 or of sufficient importance to be protected by ,letters ,patent4 ,and it might be proper to add1 that vulcanized gutta-percha or indurated rubber may be used as the basis upon which1 or in which the japanned surface may be made4 ,the invention1 however1 consists mainly on the surface1 so that a silver picture may be made upon it1 said surface forming the background of the picture4 ,the ingredients for fixing and developing the positive impression1 upon the japanned surface may be the same as those heretofore essayed by me in a former application1 and need not again be repeated here4 ,though other chemicals1 or other proportions of the same chemicals1 may be used4 ,having thus fully described the nature of my improvement in photographic pictures1 and shown how the same may be accomplished1 what ,i claim therein as new and desire to secure by ,letters ,patent1 is3-- ,the obtaining positive impressions upon a japanned surface previously prepared upon an iron or other metallic or mineral sheet or plate1 by means of collodion and a solution of a salt of silver and a camera1 substantially as herein described4 ,hamilton ,l4 ,smith4 ,geo4 ,t4 ,chapman4 ,witnesses4 ,james ,h4 ,lee4 ,dated ,february1 #aith1 #ahef4 99 99 99 99 99 ,,photographic ,,pictures ,,on ,,oil4 ,to all whom it may concern3 ,be it known that ,i1 ,joel ,haywood ,tatum1 of the ,city of ,baltimore and ,state of ,maryland1 have discovered or invented a new and useful preparation of oil ground or body1 and mode of preparing the same by which ,photographic impressions1 such as portraits of all sizes1 landscapes or still life may be produced upon such oil prepared ground body or surface1 whether upon canvass1 mill-board1 pannel1 or other body whatever1 without any permanent injury to such body1 ground or surface for the reception of colors in oil 7water7 or dry 7paste71 without impairing the texture1 quality1 durability1 or other desirable quality of the body ground1 or surface rendered so impressible1 and give the following as the ,process used in accomplishing the result4 ,i take ordinary prepared canvass1 mill-board1 pannel or other substance for the reception of oil painting by any composition of oil 7or oleaginous substance7 and oxide of lead or zinc1 ,spanish whiting1 ,fuller's earth1 or their equivalents1 singly or in combination1 and after having removed all irregularities or lumps from the surface ,i damp or wet the surface with spirits of wine1 and wipe clean2 after which1 ,i treat the surface with a solution of potassium or any good alkali1 regulating the strength to the amount of oil in the body-ground or surface to be treated 7ordinarily #a oz4 of super1 carb4 soda to #a pint of water71 as soon as the surface has uniformly changed color allow the surplus solution to run off1 wash off by pouring over the surface clean water1 let dry1 but not by the fire or in the sun1 as that would bring out the oil to the surface4 ,when dry1 treat the surface again with a solution of the chloride of sodium 7of the strength ordinarily used and prescribed for paper positives71 decant from the surface the superfluous fluid after a minute1 and let dry1 as before2 remove to a dark room1 and treat the surface with a solution of the nitrate of silver1 its strength being governed by the strength of impression desired1 usually #ah grains of nitrate of silver to #a oz4 of distilled water2 allow the solution to float upon the surface a few moments to insure uniformity of deposit1 and then decant the surplus1 in the bottle or lath2 place a small piece of filtering paper on the edge of the body1 and place that1 edge down1 to facilitate the drainage2 when dry1 place the negative impression 7which must previously have been obtained1 by the use of the camera1 either on collodion or albumen upon glass or upon paper7 upon the body or ground to receive the impression in the position the picture is desired1 with the face of the negative to the surface of the body to receive the impression4 ,if the negative impression does not cover the whole surface1 then a mat should be used so as to extend to the edge of the ground on all sides4 ,expose to the light1 and1 when sufficiently long1 remove the negative into a dark room 7lighted with a feeble lamp72 dash over the impression a weak solution of hyposulphite of soda1 and let stand a few moments2 then wash off with a very dilute acid of only sufficient strength to neutralize the alkalies remaining upon the surface1 usually five or six drops of sulphuric acid to an oz4 of water is sufficient4 ,what ,i claim as my own invention and discovery1 and desire to secure by ,letters ,patent1 is the mode of preparing and rendering oil 7oroleaginous7 bodies1 grounds1 or surfaces impressible or sensitive to the ,photographic art by the temporary destruction or chemical change of the oil or oleaginous matter of the immediate surface only1 by the use of spirits of wine and alkaline solution1 or their equivalents1 and1 after fixing the impression by the use of hyposulphate of soda1 the use of dilute acid1 by which last application the alkalies are neutralized and the oil restored with the impression permanent upon the surface4 ,disclaiming everything heretofore known in the production of ,photographic pictures upon paper or any unoiled body or surface4 ,joel ,haywood ,tatum4 ,witnesses4 ,j4 ,s4 ,hollingshead1 ,e4 ,g4 ,handy4 ,original1 dated ,april1 #ae4 #ahef4 ,re-issue1 dated ,may #ac1 #ahef4 99 99 99 99 99 ,,patent ,,for ,,making ,,the ,,border ,,of ,,the ,,picture ,,transparent1 ,,and ,,placing ,,the ,,mat ,,back ,,of ,,the ,,picture4 ,to all whom it may concern3 ,be it known that we1 ,albert ,bisbee1 of ,columbus1 in the ,county of ,franklin and ,state of ,ohio1 and ,y4 ,day1 of ,nashville1 in the ,county of ,davidson and ,state of ,tennessee1 have invented certain new and useful improvements in photographic pictures on glass1 and we do hereby declare the following to be a full1 clear and exact description of the same4 ,the nature of our invention consists in making the edges of the coating or film on the glass transparent so that the picture is made only on the central part of the glass1 and extending so far as to meet the inside edge of the mat or border1 generally used in putting up such pictures1 and then placing the mat back of the picture4 ,to enable others skilled in the art to make and use our invention1 we will proceed to describe the same as follows3-- ,we place inside of the camera1 and about one-tenth of the focal distance of the lens from the glass1 a board having an aperture of any desired pattern that we wish the edges to have4 ,this board shades the edges of the glass1 thereby leaving them transparent in the picture4 ,then the picture1 being taken in the usual manner1 is finished by varnishing with transparent white varnish1 and then backed with japan varnish1 care being taken to have the japan on the back extend only to meet the inside edges of the mat4 ,then we place the mat back of the picture and secure it in its place with the preserver4 ,if applied to the process1 as patented by ,j4 ,a4 ,cutting1 with two glasses1 the picture is made as above described1 and then the second glass is applied1 and finished as before by backing with japan4 ,the advantage of our improvement1 is in having the mat protected from being soiled1 and making the picture appear more round1 causing an illusion as though the picture or image was suspended in the atmosphere1 clear from the background4 ,having thus fully described the nature of our invention1 what we claim therein as new1 and desire to secure by ,letters ,patent1 is1 making the border of the picture transparent and placing the mat back of the picture1 as described in the above specification1 and for the purpose set forth4 ,witnesses to the signature of ,a4 ,bisbee4 ,c4 ,a4 ,barker1 ,wm4 ,field4 ,a4 ,bisbee4 ,witnesses to the signature of ,y4 ,day4 ,b4 ,bingham1 ,w4 ,atkins4 ,y4 ,day4 ,dated ,may #bgth1 #ahef4 99 99 99 99 99 ,,patent ,,for ,,the ,,application ,,of ,,coloring ,,substances1 ,,or ,,matter1 ,,to ,,photographic ,,impressions4 ,be it known that ,i1 ,giles ,langdell1 and ,marcus ,a4 ,root1 of ,philadelphia1 in the ,state of ,pennsylvania1 have invented a new and improved mode of coloring daguerreotype and other photographic portraits or pictures made on glass1 metal or other material2 and we do hereby declare that the following is a full and exact description3-- ,the nature of our invention or discovery consists in providing and applying both mineral and vegetable coloring matters in solution to the daguerreotype or any other photographic impression1 introducing the said coloring matter either into the collodion or the developer1 or by pouring upon the plate after the impression is fixed by hyposulphite of soda1 or the cyanide of potassium1 or by any other means4 ,the several coloring substances1 ,e4 ,g4 red saunders1 alkanet1 dragons' blood1 c41 c41 can be used separately or in conjunction or compounded with various mineral substances1 or with any coloring matters obtained from other roots1 woods1 gums or other vegetable matter1 the proportions or quantity employed being varied or regulated by the lightness or depth and strength of tone which may1 from time to time1 be required4 ,the desired or similar results may be obtained from different formul4 ,the following answers for all practical purposes1 but may be varied at pleasure3-- ,digest for two or three days red saunders 7pterocarpus santalinus7 half a pound in three pints of water to which the aqua-ammonia has been added4 ,then pour off the solution and precipitate by the addition of nitric acid4 ,wash the precipitate thoroughly with water and dry it4 ,then dissolve it in strong alcohol and dilute with the same as required to produce the tone or tint that may be desired4 ,alkanet 7anchusa tinctoria7 may be prepared in the same way4 ,dragons' blood dissolved in alcohol and treated in the same manner will produce the various shades of yellow4 ,the foregoing articles1 and also madder1 indigo1 cochineal1 and some other coloring substances both vegetable and mineral alone or combined1 will produce pleasing results when applied as follows 7although they may be introduced into the collodion73-- ,we prefer first to develope the impression1 then to fix and dry it1 and afterwards to flow on the toning or tinting solution1 as collodion or varnish1 c41 is poured upon the plate1 allowing the solution to run off the corner1 and then levelling the plate to make the fluid flow uniformly over and tint the whole surface of the plate evenly4 ,then wash at once and thoroughly with clean water1 and stand the plate up to dry1 after which it may be colored 7the dress of any tint or color desired--the face1 hands1 c41 are flesh tint7 with dry colors 7as is usual in coloring daguerreotypes7 applied to the collodion or upon the varnish4 ,what we claim as our invention and discovery1 and desire to secure by ,letters ,patent1 is the application of coloring substances or matter to ,photographic impressions or pictures upon glass or metal1 or other material in the form and manner herein described4 ,witnesses4 ,james ,j4 ,b4 ,ogle1 ,giles ,langdell ,l4 ,s4 ,williams ,ogle1 ,m4 ,a4 ,root4 ,l4 ,s4 ,dated ,july #aeth1 #ahef4 99 99 99 99 99 ,,patent ,,for ,,the ,,use ,,of ,,albumenized ,,collodion4 ,to all whom it may concern3 ,be it remembered1 that ,i1 ,victor ,m4 ,griswold1 of the ,city of ,lancaster1 in the ,county of ,fairfield and ,state of ,ohio1 have invented certain improvements in the art and mode of taking ,photographic ,pictures1 and ,i do hereby declare that the following is a full and exact description thereof3 ,the nature of my invention consists in an improvement in the photographic art of taking pictures4 ,to one quart of collodion prepared in the usual way or manner1 ,i add three ounces of a solution prepared thus3 ,the clear solution which results from the whites of eggs which have been well beaten1 and one equal bulk of pure soft water4 ,when this is added to the collodion1 it is thrown to the bottom in long stringy white masses1 which after a few days impart to the liquid albuminous properties1 rendering the film closer in texture1 and bringing out all the minor details more sharply and perfectly than by the ordinary collodion1 and giving to the picture a glossy and sparkling tone1 unlike any produced by other means4 ,another method which ,i frequently adopt is thus2 albumen as above1 without water1 to which is added iodide of potassium forty grains2 this throws down the albumen in jelly-like masses1 and1 when added to the collodion1 not only iodizes it1 but produces the same effect upon the collodion as by the formula above4 ,also1 another method3 one ounce of chloroform1 to which is added one half ounce of albumen1 prepared as above1 iodized2 this forms also a soft semi-transparent jelly1 which on being added to the collodion produces perhaps the best effect of any of these preparations4 ,this addition of albumen also answers a far better purpose1 than any that has hitherto been employed for freeing old samples of collodion from free iodine held in suspension by which they can be rendered as clear and limpid as they were when first mixed4 ,what ,i claim as my invention1 and desire to secure by ,letters ,patent is the addition of albumen to collodion in the manner and for the purpose herein and above specified4 ,v4 ,m4 ,griswold4 ,alfred ,m',veigh1 ,witnesses4 ,j4 ,c4 ,heuley4 ,patented ,july #aeth1 #ahef4 99 99 99 99 99 ,,coloring ,,ambrotypes4 ,to all whom it may concern3 ,be it known that we1 ,d4 ,b4 ,spooner and ,h4 ,b4 ,spooner1 of ,springfield1 in the ,county of ,hampden1 in the ,state of ,massachusetts1 having invented new and useful improvements in coloring ,ambrotype or ,photographic ,pictures on glass1 and we do hereby declare that the following is a full and exact description thereof3-- ,the nature of our invention consists1 in so preparing the collodion film containing the picture in alternate placers with gum or other suitable material1 so that when a penetrating dye or pigment1 in a solution that will penetrate the collodion film1 may be deposited on any particular portion of the picture between the collodion film and the glass1 in order to give it the requisite color properly distributed between the face1 drapery1 c4 ,the following is the process adopted3-- ,after the picture is thoroughly washed and dried1 proceed with a brush to cover any portion of the picture not designed to take the color1 with a solution of gum or any other substance insoluble in the coloring solution1 but soluble in any other liquid in which the coloring matter is not soluble4 ,e4 ,g4--,take a solution of gum arabic in water1 and apply it to a portion of the picture4 ,now take a solution of turmeric in alcohol1 and pour it upon the collodion surface of the picture1 and you immediately get a deposit of the coloring matter between the collodion and the glass1 the portion of the picture covered with the gum not being penetrated by the alcohol1 is protected from the color while all other portions are colored4 ,then1 by washing the picture in water1 the gum is dissolved and washed off1 and the parts uncolored may remain in their natural state without color1 or1 by applying the gum solution to the portion already colored with a part of the uncolored portion1 another color may be produced by the use of another pigment in the same manner as before described4 ,in this manner any number of colors may be produced2 or1 when a small portion only of the picture is to be colored1 the whole of the picture may be colored and dried1 and then that portion which is to retain the color may be covered with the gum solution1 and the coloring matter not protected by the gum may be extracted with alcohol or other solvent1 and the gum washed off as before4 ,the advantages of our invention consist in depositing the coloring matter in its various tints on the front side of the picture between the collodion and the glass1 instead of coloring the fibre of the collodion1 or the upper side of it1 as is common1 which does not show through to the positive side of the picture on account of the opacity of the silver deposit which forms the picture4 ,we do not claim the coloring of a picture all over with a single tint1 but ,what we claim as our invention and desire to secure by ,letters ,patent1 is the application of gum arabic or other equivalent material1 as set forth in the specification1 for the purposes therein described1 and no other4 ,d4 ,b4 ,spooner4 ,h4 ,b4 ,spooner4 ,witnesses4 ,george ,w4 ,adams1 ,chas4 ,h4 ,codman4 ,patented ,august #e1 #ahef4 ,,chapter ,,viii4 ,,the ,,collodio-,,albumen ,,process4 ,sidenote3 ,,collodio-,,albumen ,,process4 ,this is a process1 invented by ,dr4 ,taupenot1 for obtaining negatives on glass1 which bids fair to outrival all others1 being easy of manipulation1 and giving results of the most exquisite minuti and beauty4 ,glass plates1 when prepared and excited by this process1 may be kept at least a fortnight before being developed1 and these plates when exposed in the frame may be developed immediately1 or kept for days before commencing this operation4 ,indeed it is quite possible to prepare and excite a number of plates before leaving home to go on a tour of twelve or fourteen days2 to expose the plates at any time or place during the journey1 and bring them home to be developed4 ,the manipulation may be said to consist of nine distinct operations4 #a4 ,cleaning the plate4 #b4 ,coating with iodized collodion4 #c4 ,exciting the collodion film4 #d4 ,coating with albumen4 #e4 ,exciting the albumen coating4 #f4 ,exposure in the camera4 #g4 ,developing the image4 #h4 ,fixing the image4 #i4 ,varnishing the plate4 ,before describing these operations1 ,i propose to give clear directions for preparing the necessary solutions1 merely promising that1 where ,i have deviated from the inventor's plan1 it has been after performing careful experiments1 to test the merits of the two modes of proceeding4 ,the necessary solutions for this process are3 ,collodion bath solution4 ,iodized collodion4 ,iodized albumen4 ,albumen bath solution4 ,pyrogallic solution4 ,silver developing solution4 ,fixing solution4 ,collodion ,bath ,solution4 ,nitrate of silver in crystals #a ounce4 ,iodide of potassium #b grains4 ,distilled water #af ounces4 ,alcohol #b drachms4 ,dissolve the ounce of nitrate of silver in two ounces of the distilled water1 and the two grains of iodide of potassium in one drachm of distilled water2 mix the two solutions and shake well together until the precipitate which is first thrown down is re-dissolved2 when this takes place1 add the remaining fourteen ounces of distilled water1 and the two drachms of alcohol4 ,on the addition of the water a turbidness ensues1 which must be removed by the solution being very carefully filtered through filtering paper2 and the filtered liquid should be clear and transparent1 free from any deposit or floating particles1 and must possess a slightly acid reaction of test-paper4 ,in order to ascertain if the solution thus prepared possesses the necessary amount of free acid without superabundance1 proceed to test and to correct it1 if necessary4 ,iodized ,collodion1 ,the collodion to be used in this process must be one yielding good negative pictures--that supplied by ,home ,thornthwaite under the name of negative collodion answers admirably4 ,this is supplied either ready iodized1 or the collodion and iodizing in separate bottles4 ,as this collodion becomes less sensitive after being iodized a fortnight1 it is advisable to iodize no more than will be used in that time--therefore1 obtain the collodion and the iodizing solution separate1 as the mode of iodizing this collodion is very simple4 ,half an ounce of the iodizing solution is mixed with one ounce and a half of collodion1 and the mixture allowed to settle twelve hours before being used2 and it is even advisable to pour off the clear solution into a perfectly clean bottle1 in order to get rid of any insoluble matter which may fall to the bottom4 ,iodized ,albumen4 ,white of egg 7free from yelk7 #aj ounces4 ,honey #a ounce4 ,iodide of calcium #b scruples4 ,yeast #a tablespoonful4 ,mix these together in a tall glass jar1 or wide-mouthed bottle of at least one pint capacity2 tie a piece of paper1 pierce with small holes over the top to keep out dust2 then place the whole near a fire or other warm situation1 where the temperature is not lower than seventy degrees1 or higher than ninety degrees4 ,in a few hours fermentation commences1 which is evident by the formation of bubbles of gas1 rising through the liquid4 ,this action continues for five or six days2 when it ceases1 pour the whole on a paper-filter contained in a funnel1 underneath which must be placed a bottle to receive the liquid as it passes through4 ,the fluid being of a viscid nature filters slowly1 generally occupying twelve hours4 ,the filtered liquid is the iodized albumen1 which is said by ,dr4 ,taupenot to keep good for years4 ,it must be carefully preserved from dust or contact with any substance1 as the success of the picture depends materially on the condition of this albumen4 ,albumen ,bath ,solution4 ,nitrate of silver #a ounce and a half4 ,acetic acid1 glacial #a ounce4 ,distilled water #af ounces4 ,animal charcoal #b drachms4 ,dissolve the nitrate of silver in the distilled water1 then add the acetic acid and animal charcoal1 and keep in a closely stoppered bottle for use4 ,pyrogallic ,solution4 ,pyrogallic acid #ae grains4 ,glacial acetic acid #b drachms4 ,alcohol #b drachms4 ,distilled water #g ounces4 ,dissolve the pyrogallic acid in the distilled water1 and then add the acetic acid and alcohol4 ,silver ,developing ,solution4 ,nitrate of silver #a drachm4 ,acetic acid #b drachms4 ,distilled water #g ounces4 ,dissolve the nitrate of silver in the distilled water1 and then add the acetic acid4 ,fixing ,solution4 ,hyposulphite of soda #b ounces4 ,water #a pint--dissolve4 ,varnish4 ,the varnish best adapted for this purpose is that supplied by ,home ,thornthwaite1 and termed negative varnish4,h ,footnote ,h3 ,in this country1 ,humphrey's ,collodion ,gilding is the article in almost universal use4 ,cleaning the ,plate4 ,the plates must be cleaned in the usual way1 merely premising that extra care must be observed to remove every impurity1 as cleanliness in photography is an absolute necessity4 ,in order to hold large plates whilst being cleaned1 the screw plate-holder is exceedingly useful4 ,this is made in three sizes1 and adapts itself to all sized plates4 ,the small size is useful for plates up to #g inches by #f4 ,the second size is for plates up to #aj inches by #h4 ,and the third size for plates up to #ad inches by #aj4 ,coating with ,iodized ,collodion4 ,the plate having been thoroughly cleaned1 and received its final polish by the use of a prepared chamois leather1 is coated with negative collodion1 which has been iodized at least twelve hours1 and allowed to settle4 ,exciting the ,collodion ,film4,i ,footnote ,i3 ,this and subsequent operations 7except exposure in the camera7 must be performed in a dark room4 ,after the ether has evaporated1 and the surface of the collodion appears set1 the plate must be laid1 collodion side upwards1 on a glass dipper1 and plunged with one downward movement into a bath filled to within an inch of the top with collodion bath solution1 made as described at page #aij1 which must be carefully filtered through filtering paper before being used4 ,after the plate has been allowed to remain in the bath one minute1 it is lifted out three or four times1 in order to facilitate the removal of the oily appearance the plate now presents4 ,when the surface appears wetted uniformly1 on being drawn out of the solution the plate is removed from the dipper1 and the excess of solution drained off1 and is then placed collodion side upwards1 on a fixing stand1 and distilled or filtered rain water poured over the surface1 so as to remove as much as possible of the bath solution from the surface4 ,the plate is now removed from the fixing stand2 the back well washed with water1 and then placed nearly upright on blotting paper1 with the face against a wall for one minute to drain4 ,coating with ,albumen4 ,having allowed the plate to drain one minute1 place it again on a levelling stand1 with the film upwards1 and pour over it as much of the iodized albumen as the plate will hold1 from a glass measure containing not more than enough of the albumen to coat two plates with1 pour off the excess into the measure1 and again cover the plate with albumen three separate times2 ultimately drain off as much as possible of the excess of albumen1 and place the plate nearly upright against the wall1 with the coated side inwards1 to dry1 which takes place in an ordinary temperature in about one hour4 ,in coating with albumen1 the presence of air-bubbles or dust must be guarded against4 ,the former can be easily done by taking care1 in pouring the albumen into the measure and on the plate1 not to pour so as to generate air-bubbles in the liquid4 ,but should any be detected1 hold the plate horizontally and give it another coating of albumen1 then incline the plate so that the bulk of the liquid shall pass over and carry off the bubbles with the running stream4 ,dust on the plate must be prevented by operating in a room as free from this photographic enemy as possible4 ,in order to render the coating of albumen as uniform as possible1 the plate must stand to dry on two or three layers of filtering paper and the upper surface must touch the wall at one point only and not to be allowed to rest against it along its entire upper edge4 ,when the albumen coating is thoroughly dry 7and not till then71 the plate is ready to be excited1 but if more have been prepared than are likely to be used for taking pictures on during the next ten days or fortnight1 they may be stowed away in a plate box1 ready to receive the sensitive coating at any time4 ,the author's experience has led him to believe that these albumenized plates will keep good any length of time1 as plates which had been coated a month1 when excited1 exposed1 and developed1 appeared to possess all the properties of recently prepared plates4 ,exciting the ,albumen ,coating4 ,prior to the plates being excited they must be thoroughly dry and free from any particles of loose dust on the surface1 back1 or edge4 ,sufficient of the albumen bath solution1 page #aib1 must be filtered through filtering paper to fill a dipping bath of the required size1 so that the plate can be immersed in it4 ,the careful filtering of the fluid is very necessary in order to free it from any floating particles1 and to separate the animal charcoal4 ,the plate is now taken and laid1 albumen side upwards1 on the dipper1 and then lowered into the bath with one steady downward movement1 where it is allowed to remain one minute2 it is then taken out1 the excess of liquid drained off1 and placed on the fixing stand1 with the albumen surface uppermost1 and a stream of water poured over it for at least one minute1 so as to remove every particle of the bath solution4 ,this complete washing is very necessary1 in order to prevent stains in the after development1 which invariably takes place around the edges1 if not thoroughly washed4 ,the plate having been thoroughly washed1 is leaned against a wall to dry1 or if required for immediate exposure1 may be dried on a plate of heated metal or foot warmer1 but in no case must the exposure in the camera take place until the surface is thoroughly dry4 ,exposure in the ,camera4,j ,footnote ,j3 ,remarks as to the selection of the view1 c41 are not given1 as this can be effected by the individual taste of the operator1 but care must be taken that direct rays from the sun shall not fall on the lens or enter the camera during the exposure of a plate4 ,as has been before stated1 this operation may take place immediately the plate is thoroughly dry after being excited1 or a fortnight may intervene between the excitement and exposure1 provided the plate is kept very carefully excluded from light and any chemical or sulphurous vapors1 in a plate-box adapted for that purpose1 with the sensitive surface towards the back of the box4 ,when the exposure is about to take place1 or at any time previously1 the camera-backs may each have a plate placed in them ready for exposure2 to do this1 the camera-back must be taken into the operating room and the door closed1 so as to exclude all white light4 ,the hinged flap of the camera back is opened1 and the prepared plate laid1 with its sensitive surface downwards1 or next the sliding flap1 so that its corners may rest on the silver wire corners of the plate frame previously placed within the camera back ready to receive it4 ,the hinged flap is now closed and kept from opening by turning the flap button over it2 the sliding flap is examined to see that it is pushed closely down so as to guard any access of light1 and it is then ready to be placed in the camera1 and may be taken into the open air with impunity4 ,should the exposure not take place immediately1 or1 should the camera back have to be carried any distance1 it is advisable either to wrap it up in black cloth1 or secure the flaps from the chance of coming open during transit1 by a stout string being tied around the back4 ,the focussing is conducted in the usual way and the cap replaced on the lens2 the focussing glass is now removed and the camera back fitted into the same aperture1 with the sliding flap next the lens4 ,the sliding flap is pulled up to its fullest extent1 placing the hand on the camera back to prevent it rising out of the camera with this action4 ,the cap of the lens is then removed1 so that the light may be admitted into the camera1 and to fall on the sensitive surface of the plate4 ,after the necessary time of exposure has taken place1 the cap is replaced on the lens1 the sliding flap is pushed down1 and the camera back withdrawn from the camera2 the plate can then be taken into the operating room to be developed1 or this operation may be deferred for days or even a week1 or more if convenient4 ,the time of exposure in the camera varies according to the intensity of the light and the aperture and focal length of the lens2 therefore1 to give the exact time of exposure would be impossible1 still it may assist the amateur if ,i give the time required in summer with full sunshine1 and merely state that this time may be increased to double in winter or dull weather4 ,in the ordinary sunshine of a summer's day the time of exposure will be3 #cj seconds with a lens of #d-;inch focus and #a_/b-;inch stop4 #ba seconds with a lens of #d-;inch focus and #e_/h-;inch stop4 #e seconds with a lens of #d-;inch focus and #a-a_/d inch aperture with no stop4 #a-a_/b minute with a lens of #f-;inch focus and #a_/b-;inch stop4 #d-a_/b seconds with a lens of #f-;inch focus and #b-a_/d-;inch aperture with no stop4 #b minutes with a lens of #h-;inch focus and #a_/b-;inch stop4 #a-a_/d minute with a lens of #h-;inch focus and #e_/h-;inch stop4 #c-a_/d minutes with a lens of #aj-;inch focus and #a_/b-;inch stop4 #b minutes with a lens of #aj-;inch focus and #e_/h-;inch stop4 #e seconds with a lens of #aj-;inch focus1 #c-a_/d-;inch aperture1 with no stop4 #f-a_/d minutes with a lens of #ad-;inch focus and #a_/b-;inch stop4 #d minutes with a lens of #ad-;inch focus and #e_/h-;inch stop4 #b-a_/d minutes with a lens of #ad-;inch focus and #c_/d-;inch stop4 #h-a_/d minutes with a lens of #af-;inch focus and #a_/b-;inch stop4 #e-a_/d minutes with a lens of #af-;inch focus and #e_/h-;inch stop4 #b-a_/d minutes with a lens of #af-;inch focus and #c_/d-;inch stop4 ,developing the ,image4 ,the camera back is taken into the operating room1 from which all white light is carefully excluded1 the plate removed from the camera back1 and laid1 albumen side upwards1 on the fixing stand2 as much distilled water is now poured on it as the surface will hold1 taking care that every part of the sensitive surface is covered with the liquid2 allow the water to remain on the surface for one minute1 then pour off and drain slightly2 replace the plate on the stand1 and pour over the surface so as thoroughly to cover every part1 the pyrogallic solution 7made as described at page #aib1 and carefully filtered just before being used72 allow this to remain on the plate for one minute1 then drain off into a perfectly clean measure1 and add to it an equal bulk of silver developing solution1 page #aib2 mix these thoroughly together with a glass rod1 and then pour the mixed liquids over the plate2 allow them to rest until the picture begins to appear1 which generally takes about from three to five minutes2 then pour off and on repeatedly1 until the developing fluid becomes opaque1 which then contains floating particles1 and these1 if allowed to do so1 would settle on the plate1 to the injury of the picture2 but this may be prevented by brushing the surface with a camel's-hair brush frequently during the development4 ,when this opacity of the developing fluid takes place1 drain all the fluid off the plate1 and thoroughly wash with water2 then mix another quantity of pyrogallic and silver developing solution in the same proportions as before1 and pour this on and off the plate as before1 until the picture appears sufficiently intense1 and the middle shades well brought out2 when this takes place drain off1 and wash with water1 so as to clean the surface thoroughly1 and the plate is then ready for the next step1 fixing the image4 ,should the picture begin to develope in less than three minutes after the application of the mixed developing fluids1 thoroughly drain the plate1 and wash well with water1 then continue the development with a solution of three parts pyrogallic solution and one part silver developing solution2 but should the picture not begin to appear in five minutes1 the addition of half a drachm of the albumen bath solution to each ounce of mixed developing solution will be necessary1 in order to obtain the middle shades and the required intensity4 ,it may be stated1 as a guide1 that the best negatives which the author has produced occupied from ten to twelve minutes in developing4 ,fixing the ,image4 ,the plate1 having been thoroughly freed from the developing fluid by careful washing1 is now placed on the fixing stand1 and the surface covered by the fixing solution1 made as described at page #aib1 being poured over it4 ,in a few seconds the yellow opalescent color of the film will begin to disappear1 and its complete removal may be hastened by blowing gently on the plate1 so as to disturb the fluid4 ,when every particle of yellowness has disappeared1 the fixing solution is drained off1 and the surface thoroughly washed1 and it is then leaned against the wall to drain and dry4 ,varnishing the ,plate4 ,the plate1 being thoroughly dry1 is ready to receive a coating of transparent varnish4,k in order to protect the albumen surface from injury during the printing process4 ,to do this effectually the plate must be held before a fire1 or over a lamp1 until it is slightly warm all over2 then pour over its surface the negative varnish1 in the same manner as collodion is applied2 allow the superfluous varnish to drain back into the bottle2 hold the plate again before the fire until the whole of the spirit is evaporated2 and1 when cold1 the plate is ready to be printed from1 so as to produce any number of positive pictures on paper4 ,footnote ,k3 ,humphrey's ,collodion ,gilding is the best for this purpose4 ,it will be observed1 that in describing this process1 the operator has been supposed to be so situated1 that in case a second view of the same spot were required1 he could return to his operating room1 remove the plate which had been exposed1 from the camera back to the plate box1 and place another in the camera back1 ready for taking another view4 ,but1 unfortunately1 this is not at all times practicable4 ,we1 therefore1 require some means of removing the plates1 after being exposed1 from the camera back into the plate box1 and substituting others in their stead1 whilst we are in the open air4 ,in order to effect this1 the field plate box has been devised by the author1 by the aid of which the plates may be removed from the box1 exposed in the camera1 and again returned into the box1 without any possibility of access of light falling on it4 ,this box is but a trifle larger than the ordinary one1 and is furnished with two sliding bottoms1 working in grooves1 one over the other2 the lower bottom has a grooved channel1 into which the side of the camera back slides2 the camera back has an aperture through the side1 closed by a narrow slide1 and the lower bottom of the field box has a corresponding one4 ,we now suppose the field box to have been previously filled with excited glass plates1 having their sensitive sides towards the back of the box1 and the box lid closed4 ,the bottom slide is now pushed on until the aperture is in a line with any particular groove of the field box 7which position is indicated by a numbered scale and index point74 ,the camera back is then slid on to its place on the field box1 so that the hinged flap is towards the front of the box1 and its narrow slide drawn out4 ,the upper slide is then withdrawn1 and the box inclined1 so that the plate in that groove opposite the aperture in the lower slide1 may pass through into the camera back4 ,when this has taken place1 push in the narrow slide of the camera back1 invert the box1 and push in the inner slide2 then withdraw the camera back from its channel1 and expose the plate in the camera4 ,when this is done1 slide the back again into its channel1 draw out the inner box slide1 then the narrow camera back slide1 invert the box1 and the plate will then leave the camera back and pass into the field box1 occupying the same groove as before4 ,in order to get out another plate1 slide the lower bottom1 so that the index points to the number on the scale1 as that of the groove in which the required plate is situate4 ,then proceed as before directed4 ,,chapter ,,ix4 ,on a mode of ,printing enlarged and reduced ,positives1 etc41 from ,collodion ,negatives4 ,to explain the manner in which a photograph may be enlarged or reduced in the process of printing1 it will be necessary to refer to the remarks made at page #bj1 on the conjugate foci of lenses4 ,if a collodion negative be placed at a certain distance in front of a camera1 and 7by using a tube of black cloth7 the light be admitted into the dark chamber only through the negative1 a reduced image will be formed upon the ground glass2 but if the negative be advanced nearer1 the image will increase in size1 until it becomes first equal to1 and then larger than1 the original negative2 the focus becoming more and more distant from the lens1 or receding1 as the negative is brought nearer4 ,again1 if a negative portrait be placed in the camera slide1 and if the instrument be carried into a dark room1 a hole be cut in the window-shutter so as to admit light through the negative1 the luminous rays1 after refraction by the lens1 will form an image of the exact size of life upon a white screen placed in the position originally occupied by the sitter4 ,these two planes1 in fact1 that of the object and of the image1 are strictly conjugate foci1 and1 as regards the result1 it is immaterial from which of the two1 anterior or posterior1 the rays of light proceed4 ,therefore in order to obtain a reduced or enlarged copy of a negative1 it is necessary only to form an image of the size required1 and to project the image upon a sensitive surface either of collodion or paper4 ,a good arrangement for this purpose may be made by taking an ordinary portrait camera1 and prolonging it in front by a deal box blackened inside and with a double body1 to admit of being lengthened out as required2 or1 more simply1 by adding a framework of wood covered in with black cloth4 ,a groove in front carries the negative1 or receives the slide containing the sensitive layer1 as the case may be4 ,in reducing photographs1 the negative is placed in front of the lens1 in the position ordinarily occupied by the object2 but in making an enlarged copy it must be fixed behind the lens1 or1 which is equivalent1 the lens must be turned round so that the rays of light1 transmitted by the negative1 enter the back glass of the combination1 and pass out at the front4 ,this point should be attended to in order to avoid indistinctness of image from spherical aberration4 ,a portrait combination of lenses of #b-a_/b or #c-a_/d inches is the best form to use1 and the actinic and luminous foci should accurately correspond1 as any difference between them would be increased by enlarging4 ,a stop of an inch or an inch and a half aperture placed between the lenses obviates to some extent the loss of sharp outline usually following enlargement of the image4 ,the light may be admitted through the negative by pointing the camera towards the sky2 or direct sunlight may be used1 thrown upon the negative by a plane reflector4 ,a common swing looking-glass1 if clear and free from specks1 does very well2 it should be so placed that the centre on which it turns is on a level with the axis of the lens4 ,the best negatives for printing enlarged positives are those which are distinct and clear2 and it is important to use a small negative1 which strains the lens less and gives better results than one of larger size4 ,in printing by #b-a_/d lens for instance1 prepare the negative upon a plate about two inches square and afterwards enlarge it four diameters4 ,paper containing chloride of silver is not sufficiently sensitive to receive the image1 and the print should be formed upon collodion1 or on iodized paper developed by gallic acid4 ,the exposure required will vary not only with the intensity of the light and the sensibility of the surface used1 but also with the degree of reduction or enlargement of the image4 ,in printing upon collodion the resulting picture is positive by transmitted light2 it should be backed up with white varnish1 and then becomes positive by reflected light4 ,the tone of the blacks is improved by treating the plate first with bichloride of mercury1 and then with ammonia4 ,mr4 ,wenham1 who has written a most practical paper on the mode of obtaining positives of the life size1 operates in the following way3--he places the camera1 with the slide containing the negative in a dark room1 and reflects the sunlight in through a hole in the shutter1 so as to pass first through the negative and then through the lens2 the image is received upon iodized paper1 and developed by gallic acid4 ,on ,printing ,collodion ,transparencies for the ,stereoscope4--,this may be done by using the camera to form an image of the negative in the mode described at the last page2 but more simply by the following process3--,coat the glass1 upon which the print is to be formed1 with collodio-iodide of silver in the usual way1 then lay it upon a piece of black cloth1 collodion side uppermost1 and place two strips of paper of about the thickness of cardboard and one-fourth of an inch broad1 along the two opposite edges1 to prevent the negative being soiled by contact with the film4 ,both glasses must be perfectly flat1 and even then it may happen that the negative is unavoidably wetted2 if so1 wash it immediately with water1 and if it be properly varnished no harm will result4 ,a little ingenuity will suggest a simple framework of wood1 on which the negative and sensitive plate are retained1 separated only by the thickness of a sheet of paper2 and the use of this will be better than holding the combination in the hand4 ,the printing is conducted by the light of gas or of a camphine or moderator lamp1 diffused daylight would be too powerful4 ,the employment of a concave reflector1 which maybe purchased for a few shillings1 ensures parallelism of rays1 and is a great improvement4 ,the lamp is placed in the focus of the mirror1 which may at once be ascertained by moving it backwards and forwards until an evenly illuminated circle is thrown upon a white screen held in front4 ,this in fact is one of the disadvantages of printing by a naked flame--that the light falls most powerfully upon the central part2 and less so upon the edges1 of the negative4 99 99 99 99 99 7,from ,humphrey's ,journal1 ,no4 #ag1 ,vol4 #h47 ,on the ,use of ,alcohol for ,sensitizing ,paper4 ,sidenote3 ,,to ,,sensitize ,,paper4 ,i have practised for some time the following simple method1 which appears to me to be very superior for cleanliness and celerity in working1 for depth of tone1 and especially for purity of white in its results4 ,by means of it ,t have produced very satisfactory results upon paper which was otherwise nearly worthless4 ,to your sensitizing solution 7which should be not less than #fj grains to the ounce71 whether simple nitrate or ammonio-nitrate1 add #ej per cent1 of alcohol4 ,float the paper upon the solution for #dj seconds4 ,this method answers equally well for albumenized or plain paper4 ,you will find that the solution penetrates the paper which flattens instantaneously upon it4 ,it becomes as transparent as though it were oiled1 and every minute air-bubble or defect in the paper is rendered visible4 ,remove the air-bubbles by pressing upon the paper about an inch from the bubble1 and thus driving it out under the paper4 ,in doing this1 if the solution flows partially over the back of the paper1 shake it until the paper is wholly immersed1 which will prevent any unevenness in printing4 ,the paper reassumes its transparency in the toning bath1 but it will dry a pure white4 ,the sensitising solution will not become materially discolored even after frequent applications of albumenized paper4 ,should it become so much discolored as to give a dark hue to the paper1 shake it in a bottle with two drachms ,of animal charcoal and leave it a night to settle4 ,it will filter clear4 ,a very small portion of your solution may be made available in sensitizing a sheet of paper by pouring it upon a clean glass1 the size of the paper or a little larger1 which is carefully levelled and nicely laying down the paper upon it4 ,this is useful when your solution is too small to float in your trays4 ,the alcohol causes it to flow and be absorbed with perfect evenness4 ,to remove the papers from the solution and dry them3--,provide a dozen or more clothes-pins1 of the kind that are supplied with a ring of india-rubber for a spring4 ,into the top drive a pin firmly and bend it to a hook4 ,lift a corner of the paper by passing under it the point of a quill tooth-pick1 and attach to it one of the clothes-pins2 lift the edge out by this1 and attach another to the other corner4 ,you may thus carry the sheet by the pins and hang it upon a line to dry without touching it with the fingers1 a matter of some importance to ,amateurs of the art1 who must have unstained hands for their day's business4 ,it may be worth while here to add the following simple and economical method of printing1 which ,i have found to surpass in convenience and afford all the advantages of the most expensive printing frames4 ,four common clothes-pins1 such as work with a wire spring supply pressure enough for a #d_/d-plate4 ,lay your prepared paper upon the negative1 and next to it about twenty separate leaves of thin common wrapping paper cut to the size of the negative2 next a sheet of tolerably stiff and smooth writing paper1 and lastly1 a piece of glass as a back to the whole4 ,let the glass back be pushed from the lower edge of the papers about #a_/bj of an inch1 or just so far as to enable you to pinch the negative and papers with the thumb-nail and forefinger4 ,attach a pin to each corner and your negative is prepared for exposure4 ,now1 to examine your picture without endangering its displacement3--remove the pins from one end1 and place it1 face downwards1 on a table1 the other end with pins attached projecting an inch beyond the edge4 ,hold down the back glass with the left hand1 while with the right you remove the pins and pinch the papers and negative together between the forefinger and thumb-nail4 ,upon the smooth sheet of paper you can easily slide the back glass an inch from the edge4 ,hold it there1 and on the uncovered margin attach three of the pins with as deep a bite as they will take4 ,you may now examine your picture to within an inch of its margin1 as you would turn over the leaves of a book4 ,to replace the back1 lay it again on the table and slide the back glass up to the pins before you remove them4 ,the rest of the process is obvious4 ,the minuti of my communication may excite a smile with some1 but ,i shall always act upon the principle1 that nothing is more out of place than an apology for minuteness in describing manipulations4 ,g4 ,b4 ,c4 99 99 99 99 99 ,recovery of ,silver from waste ,solutions1--from the black ,deposit of ,hypo ,baths1 etc4 ,sidenote3 ,,recovery ,,of ,,waste ,,silver1 ,,etc4 ,the manner for separating metallic silver from waste solutions varies according to the presence or absence of alkaline hyposulphite and cyanides4 a4 ,separation of metallic ,silver from old ,nitrate ,baths4--,the silver contained in solutions of the nitrate1 acetate1 etc42 may easily be precipitated by suspending a strip of sheet copper in the liquid2 the action is completed in two or three days1 the whole of the nitric acid and oxygen passing to the copper1 and forming a blue solution of the nitrate of copper4 ,the metallic silver however separated in this manner1 always contains a portion of copper1 and gives a blue solution when dissolved in nitric acid4 ,a better process is to commence by precipitating the silver entirely in the form of chloride of silver1 by adding common salt until no further milkiness can be produced4 ,if the liquid is well stirred1 the chloride of silver sinks to the bottom1 and may be washed by repeatedly filling the vessel with common water1 and pouring off the upper clear portion when the clots have again settled down4 ,the chloride of silver thus formed may afterwards be reduced to metallic silver by a process which will presently be described4 b4 ,separation of ,silver from solutions containing alkaline ,hyposulphites1 ,cyanides or ,iodides4--,in this case the silver cannot be precipitated by adding chloride of sodium1 since the chloride of silver is soluble in such liquids4 ,therefore it is necessary to use the sulphuretted hydrogen1 or the hydrosulphate of ammonia1 and to separate the silver in the form of sulphuret4 ,sulphuretted hydrogen gas is readily prepared1 by fitting a cork and flexible tubing to the neck of a pint bottle1 and having introduced sulphuret of iron 7sold by operative chemists for the purpose71 about as much as will stand in the palm of the hand1 pouring upon it #a-a_/b fluid ounces of oil of vitriol diluted with #aj ounces of water4 ,the gas is generated gradually without the application of heat2 and must be allowed to bubble up through the liquid from which the silver is to be separated4 ,the smell of sulphuretted hydrogen being offensive1 and highly poisonous if inhaled in a concentrated form1 the operation must be carried on in the open air1 or in a place where the fumes may escape without doing injury4 ,when the liquid begins to acquire a strong and persistent odor of sulphuretted hydrogen1 the precipitation of sulphuret is completed4 ,the black mass must therefore be collected upon a filter1 and washed by pouring water over it1 until the liquid which runs through gives little or no precipitation with a drop of nitrate of silver4 ,the silver may also be separated in the form of sulphuret from old hypo baths1 by adding oil of vitriol in quantity sufficient to decompose the hyposulphite of soda2 and burning off the free sulphur from the brown deposit4 ,conversion of ,sulphuret of ,silver into ,metallic ,silver4--,the black sulphuret of silver may be reduced to the state of metal by roasting and subsequent fusion with carbonate of soda2 but it is more convenient1 in operating on a small scale1 to proceed in the following manner3--first convert the sulphuret into nitrate of silver1 by boiling with nitric acid diluted with two parts of water2 when all evolution of red fumes has ceased1 the liquid may be diluted1 allowed to cool1 and filtered from the insoluble portion1 which consists principally of sulphur1 but also contains a mixture of chloride and sulphuret of silver1 unless the nitric acid employed was free from chlorine2 this precipitate may be heated in order to volatilize the sulphur1 and then digested with hyposulphite of soda1 or added to the hypo bath4 ,the solution of nitrate of silver obtained by dissolving sulphuret of silver is always strongly acid with nitric acid1 and also contains sulphate of silver4 ,it may be crystallized by evaporation2 but unless the quantity of material operated on is large1 it will be better to precipitate the silver in the form of chloride1 by adding common salt1 as already recommended4 99 99 99 99 99 ,on the ,use of ,test ,papers4 ,sidenote3 ,,on ,,the ,,use ,,of ,,test ,,papers4 ,the nature of the coloring matter which is employed in the preparation of litmus-paper has already been described at page #ih4 ,in testing for the alkalies and basic oxides generally1 the blue litmus-paper which has been reddened by an acid may be used1 or1 in place of it1 the turmeric paper4 ,turmeric is a yellow vegetable substance which possesses the property of becoming brown when treated with an alkali2 it is however decidedly less sensitive than the reddened litmus1 and is scarcely affected by the weaker bases1 such as oxide of silver4 ,in using test papers observe the following precautions3--they should be kept in a dark place1 and protected from the action of the air1 or they soon become purple from carbonic acid1 always present in the atmosphere in small quantity4 ,by immersion in water containing about one drop of liquor potass in four ounces1 the blue color is restored4 ,test-papers prepared with porous paper show the red color better than those upon glazed or strongly sized paper4 ,if the quantity of acid present however is small1 it is not sufficient in any case simply to dip the paper in the liquid2 a small strip should be thrown in1 and allowed to remain for ten minutes or a quarter of an hour4 ,if the paper1 on immersion1 assumes a wine-red or purple tint1 in place of a decided red1 it is probably caused by carbonic aid gas3 in that case the blue color returns when the paper is washed and held to the fire4 ,blue litmus-papers may be changed to the red papers used for alkalies by soaking in water acidified with sulphuric acid1 one drop to half a pint4 99 99 99 99 99 ,the ,salting and ,albumenizing ,paper4 ,sidenote3 ,,salting ,,paper1 ,,etc4 ,take of ,chloride of ammonium1 or pure chloride of sodium #bjj grains4 ,water #aj fluid oz4 ,albumen #aj fluid oz4 ,if distilled water cannot be procured1 rain water or even common spring water,l will answer the purpose4 ,to obtain the albumen1 use new-laid eggs1 and be careful that in opening the shell the yelk is not broken2 each egg will yield about one fluid ounce of albumen4 ,footnote ,l3 ,if the water contained much sulphate of lime1 it is likely that the sensitiveness of the paper would be impaired 7874 ,when the ingredients are mixed1 take a bundle of quills or a fork1 and beat the whole into a perfect froth4 ,as the froth forms1 it is to be skimmed off and placed in a flat dish to subside4 ,the success of the operation depends entirely upon the manner in which this part of the process is conducted2 if the albumen is not thoroughly beaten1 flakes of animal membrane will be left in the liquid1 and will cause streaks upon the paper4 ,when the froth has partially subsided1 transfer it to a tall and narrow jar1 and allow to stand for several hours1 that the membranous shreds may settle to the bottom4 ,pour off the upper clear portion1 which is fit for use4 ,albumenous liquids are too glutinous to run well through a paper filter1 and are better cleared by subsidence4 ,a more simple plan than the above1 and one equally efficacious1 is to fill a bottle to about three parts with the salted mixture of albumen and water1 and to shake it well for ten minutes or a quarter of an hour1 until it loses its glutinosity and can be poured out smoothly from the neck of the bottle4 ,it is then to be transferred to an open jar1 and allowed to settle as before4 ,the solution1 prepared by the above directions1 will contain exactly ten grains of salt to the ounce1 dissolved in an equal bulk of albumen and water4 ,some operators employ the albumen alone without an addition of water1 but the paper in that case has a very highly varnished appearance1 which is thought by most to be objectionable4 ,the principal difficulty in albumenizing paper is to avoid the occurrence of streaky lines1 which1 when the paper is rendered sensitive1 bronze strongly under the influence of the light4 ,the writer believes these to be caused by a commencing decomposition of the animal matter composing the cells in which the albumen is retained and the best remedy appears to be to use the eggs quite fresh2 the same object may sometimes 7but not invariably7 be attained by allowing the albumen to stand for several weeks until it has become sour2 after which it will be sufficiently limpid to run through a filter4 ,in salting and albumenizing photographic paper by the formula above given1 it was found that each quarter sheet1 measuring eleven by nine inches1 removed one fluid drachm and a half from the bath2 equivalent to about one grain and three quarters of salt 7including droppings74 ,in salting plain paper1 each quarter sheet took up only one drachm2 so that the glutinous nature of the albumen causes a third part more of the salt to be retained by the paper4 ,selection of the ,paper4--,the ,english papers are not good for albumenizing2 they are too dense to take the albumen properly1 and curl up when laid upon the liquid2 the process of toning the prints is also slow and tedious4 ,the thin negative paper of ,canson1 the ,papier ,rieve1 and ,papier ,saxe1 have succeeded with the writer better than ,canson's positive paper1 which is usually recommended2 they have a finer texture and give more smoothness of grain4 ,to apply the albumen2 pour a portion of the solution into a flat dish to the depth of half an inch4 ,then1 having previously cut the paper to the proper size1 take a sheet by the two corners1 bend it into a curved form1 convexity downwards1 and lay it upon the albumen1 the centre part first touching the liquid and the corners being lowered gradually4 ,in this way all bubbles of air will be pushed forwards and excluded4 ,one side only of the paper is wetted3 the other remains dry4 ,allow the sheet to rest upon the solution for one minute and a half1 and then raise it off1 and up by two corners4 ,if any circular spots1 free from albumen1 are seen1 caused by bubbles of air1 replace the sheet for the same length of time as at first4 ,the paper must not allowed to remain upon the salting bath much longer than the time specified1 because the solution of albumen being alkaline 7as is shown by the strong smell of ammonia evolved on the addition of the chloride of ammonium71 tends to remove the size from the paper and sink in too deeply2 thus losing its surface gloss4 ,albumenized paper will keep a long time in a dry place4 ,some have recommended to press it with a heated iron1 in order to coagulate the layer of albumen upon the surface2 but this precaution is unnecessary1 since the coagulation is perfectly affected by the nitrate of silver used in the sensitizing2 and it is doubtful whether a layer of dry albumen would admit of coagulation by the simple application of a heated iron4 ,to render the paper sensitive4--,this operation must be conducted by the light of a candle1 or by yellow light4 ,take of ,nitrate of ,silver #fj grains4 ,distilled ,water #a ounce4 ,prepare a sufficient quantity of this solution1 and lay the sheet upon it in the same manner as before4 ,three minutes' contact will be sufficient with the thin negative paper1 but if the ,canson positive paper is used1 lour or five minutes must be allowed for the decomposition4 ,the papers are raised from this solution by a pair of bone forceps or common tweezers tipped with sealing-wax2 or a pin may be used to lift up the corner1 which is then taken by the finger and thumb and allowed to drain a little before again putting in the pin1 otherwise a white mark will be produced upon the paper1 from decomposition of the nitrate of silver4 ,when the sheet is hung up1 a small strip of blotting-paper suspended from the lower edge of the paper will serve to drain off the last drop of liquid4 ,the solution of nitrate of silver becomes after a time discolored by the albumen1 but may be used for sensitizing until it is nearly black4 ,the color can be removed by animal charcoal1,m but a better plan is to use the kaolin or pure white china clay4 ,the writer has also tried the common pipe-clay1 which answered perfectly1 but appeared to injure the sensitiveness of paper subsequently floated upon the bath 7874 ,footnote ,m3 ,common animal charcoal contains carbonate and phosphate of lime the former of which renders the nitrate of silver alkaline2 purified animal charcoal is usually acid from hydrochloric acid4 ,sensitive albumenized paper1 prepared as above1 will usually keep for several days1 if protected from the light1 but afterwards turns yellow from partial decomposition4 ,comparison of ,british and ,french ,weights and ,measures4 ,sidenote3 ,,weights ,,and ,,measures4 ,,weights4 ,grain1 ,apothecaries' #jjfdh grammes1 ,french4 ,ounce #caajb ,avoirdupois #bhcdf ,drachm1 ,apothecaries' #chhh ---- ,gramme #aedcaj grains1 ,apoth4 ,decigramme #aedcd ,centigramme #jaedc ---- ,,measures ,,of ,,capacity4 ,cubic ,inches4 ,fluid ,ounces4 ,litre #fajbh #cegi ,decilitre #fjb #ceg ,centilitre #jfaj #jce ,millilitre #jjfa #jjc ---- ,lb4 ,oz4 ,killogramme #b #c-a_/d ,avoirdupois4 ---- ,,measures ,,of ,,length4 ,metre #cicg inches4 ,decimetre #cic ,centimetre #jci ,millimetre #jjc ---- ,cubic inch of water at #cb #bebde grains4 mercury #cdbece ,fluid oz4 of water #dcgej measures #agc cub4 in4 #a f4 drachm #edfh grains4 #a pint 7,new ,york7 #bgfh cub4 in4 #a oz4 bromine #b-a_/b f4 drachms4 #a grain1 ,troy or ,apoth4 #ajig gr4 ,avoir4 #a lb4 ,avoir4 #gjjj ,troy grs4 #a #gfhj of its own grs4 ,the drachm ,avoirdupois is never used except in weighing silk4 ,pendulum vibrating seconds at ,new ,york #ciajb inches4 ,in weighing solids1 few weights are really necessary if they are properly assorted2 nothing less than half a grain is likely to be useful1 and the series following will weigh any quantity from the half grain to two thousand one hundred and ten and a half grains1 by differences of only a single grain4 ,the numbers are in grains1 but the same principle may be carried out with any other denomination1 whether ounces1 pounds1 or tons4 #a_/b1 #a1 #b1 #c1 #d1 #aj1 #bj1 #cj1 #dj1 #ajj1 #bjj1 #cjj1 #djj1 #ajjj1 c4 ,the artist should be provided with not less than three glass measures--one of a pint1 graduated to ounces--one of two ounces1 graduated to drachms--and one of two drachms1 graduated to minims4 99 99 99 99 99 ,lewis's ,patent ,glass ,baths for ,nitrate of ,silver ,solutions4--,since the foregoing pages have been in print this new article of ,baths has been introduced1 and will probably supersede all others now in market4 ,they are encased in a box made expressly to hold them1 and form a valuable and important improvement in the apparatus used in the various ,glass processes4 ,,index4 ,aberration1 chromatic1 #bc2 spherical1 #bb4 ,acetic acid1 #ff4 ,albumen1 #fc2 preparation of positive paper with1 #bjf4 ,alcohol1 #gj2 used in sensitizing paper1 #bja4 ,ammonia1 #ga4 ,ammonio-nitrate of silver1 preparation and use of1 #aeb4 ,animal charcoal1 #gd4 ,barium1 chloride of1 #gg4 ,baths1 glass1 #baa2 gutta-percha1 #cd4 ,bichloride of mercury for whitening positives1 #aei4 ,bromide and iodide of potassium and silver1 #fj4 ,bromide of potassium1 #gc4 ,bromine1 properties of1 #gb4 ,bromo-iodized collodion for positives1 7ambrotypes71 #eh1 #ei2 for negatives1 #fj4 ,camera boxes1 #bh4 ,camera1 construction of1 #bh4 ,camera stands1 #ca4 ,carbonate of soda1 #gc4 ,chemical and visual focus1 #ba4 ,china clay1 #ge4 ,chloride of ammonium1 #gg4 ,chloride of barium1 #gg4 ,chloride of gold1 preparation of1 #hc2 for toning1 #aee ,chloride of sodium1 #gh4 ,chlorine1 #ge4 ,chromatic aberration1 #bb4 ,citric acid1 #gh4 ,cleaning glass plates1 #abi4 ,coating large glasses with collodion1 #afj4 ,collodion1 manufacture of1 #ec2 iodized for positives1 #eh1 #ei2 for negatives1 #fj2 mode of coating glasses with1 #aca2 vials1 #ch4 ,collodio-,albumen process1 ,dr4 ,taupenot1 #aij4 ,color-boxes1 #ch4 ,cutting's patents and correspondence1 #agc4 ,cyanide of potassium1 #gi2 use of1 #fc4 ,decomposition of light1 #af4 ,developing solution for positives1 #fb2 for negatives1 #add1 #ade4 ,dippers1 glass and gutta-percha1 #cd4 ,double iodide of potassium and silver1 #fa4 ,ether1 preparation of1 #gi4 ,fixing positives on glass1 #acd2 negatives on glass1 #adf2 positives on paper1 #aee4 ,fluoride of potassium1 #ha4 ,fogging of collodion positives1 #acg4 ,formic acid1 #ha4 ,fulminating gold1 #hd4 ,gelatine1 properties of1 #hb2 for mounting photographs1 #aeg4 ,glass1 cementing1 #aeh4 ,glass plates1 cleaning of1 #abi2 coating with collodion1 #aca2 coating with albumen1 #aic4 ,glass rods1 bending of1 #aeh4 ,glycerine1 its properties1 #hb4 ,gold1 chloride of1 preparation of1 #he2 for toning1 #aee4 ,grape sugar1 #hf4 ,hadow1 ,mr41 ,researches and ,formula for making soluble cotton1 #df2 on iodizing collodion1 #ed4 ,head rests1 #cc4 ,helio1 collodion process for positives and negatives1 #afd4 ,honey1 #hf4 ,humphrey's collodion gilding1 #fc4 ,hydrochloric acid1 #hg4 ,hydriodic acid1 #hg4 ,hydrosulphuric acid1 #hh4 ,hypo bath1 #bjc4 ,hyposulphite of gold1 #he4 ,hyposulphite of silver1 #ag4 ,hyposulphite of soda1 preparation and properties of1 #hi4 ,instantaneous positives1 #aei4 ,iodide of ammonium1 preparation of1 #ia2 for iodizing collodion1 #eh1 #ei4 ,iodide of cadmium1 #ib4 ,iodide of iron1 preparation of1 #ic2 its uses and acceleration1 #aei4 ,iodide of potassium and silver1 preparation of1 #fa2 use in sensitizing collodion1 #eh1 #fj4 ,iodide of potassium1 properties and preparation of1 #id4 ,iodide of silver1 preparation and properties of1 #aab2 its use in the nitrate bath1 #fe1 #adg4 ,iodine1 preparation and properties of1 #ij4 ,iodized collodion1 #eh1 #ei1 #fj1 #aca4 ,iron1 perchloride of1 #ih4 protonitrate of1 #ig4 ,jenny ,lind stands1 #cb4 ,kaolin1 properties of1 #ge4 ,lenses1 double-convex1 concavo-convex1 double-concave1 #ai4 ,lenses1 forms of1 #ai1 #bj2 combination of1 for portraits1 #bg2 chromatic aberration of1 #bc2 spherical aberration of1 #bb4 ,leveling stands1 #ce4 ,light1 decomposition of1 #af4 ,litmus1 #ih4 ,manipulations of the positive collodion process1 #abi2 negative process1 #adc4 ,measures and ,weights1 #baj4 ,milk1 #ii4 ,mounting positives on paper1 #aeg4 ,negatives for printing positives1 #aea1 #afi4 ,nitrate of potash1 #ajb4 ,nitrate of silver1 #aaf4 ,nitrate of silver bath1 mode of preparing for positives1 #fd2 for negatives1 #adg2 for negatives and positives in ,helio's process1 #afd4 ,nitrate of silver used in developing negatives1 #ade4 ,nitric acid1 preparation and properties of1 #ajj2 use in nitrate bath1 #fe1 #adg2 use in making soluble cotton1 #df4 ,nitro-sulphuric acid used in preparing soluble cotton1 #db1 #ea4 ,oxide of silver1 preparation of1 #aji4 ,oxygen1 #aji4 ,oxymel1 preparation of1 #aje4 ,paper1 sensitive1 for printing1 #aeb2 alcohol used in1 #bja4 ,patent for the use of camphor in combination with iodized collodion1 #agf2 for sealing photographic pictures1 #agg2 for the use of alcohol as a desiccating agent1 #agh2 for the use of bromide of potassium in collodion1 #agh2 for the use of japanned surfaces for taking positives1 #agi2 for photographic pictures in oil1 #aha2 for making transparent borders1 #ahc2 coloring positives1 #ahe1 #ahg2 for albumenized collodion1 #ahf4 ,plate-,holders1 ,lewis's patent1 solid glass corners for1 #acg4 ,plato vices1 #fd4 ,portrait lenses1 combination of1 #bg4 ,positives1 7ambrotypes17 process for producing1 #abi2 by the ,helio process1 #afd2 printing on albumenized paper1 #aib1 #bjf2 ammonio-nitrate of silver used in1 #aeb2 use of chloride of gold in toning1 #aee2 fixing1 #aee2 fixing and brightening1 7ambrotypes71 ,humphrey's collodion gilding used in1 #fc2 printing frames for1 #cf2 collodion for1 #eh1 #ei2 mica used for1 #acf4 ,positives1 enlarging from negatives1 #aii4 ,potash1 #aje2 carbonate of1 #ajf4 ,practice of the positive collodion process1 #abi2 negative process4 #adc2 ,helio's positive and negative process1 #afd2 printing on paper1 #aea4 ,prism1 #ad2 refraction of light by1 #ad4 ,protosulphite of iron used in developing positives4 #fb2 negatives1 #add4 ,pyrogallic acid1 preparation of1 #ajg4 ,sensitizing paper1 use of alcohol in1 #bja4 ,silver1 properties of1 #ajg2 removal of stains from the nitrate of1 #afa2 recovery of from waste solutions1 #bjc4 ,solar spectrum1 #ad4 ,soluble cotton1 #db2 ,hadow on1 #df4 ,spherical aberration1 #bb4 ,spots upon positives1 #aci4 ,stains and lines upon positives1 #aci4 ,taupenot1 ,m41 his ,collodio-albumen process1 #aij4 ,test-paper1 use of1 #bje4 ,toning bath for positives on paper1 #aee4 ,weights and ,measures1 #baj4 99 99 99 99 99 ,,corrections4 ,transcriber ,note3 ,corrections have been applied to text4 ,on ,page #fa and #afth line from the top1 for ,iodide of ,silver1 read ,iodide of ,potassium4 ,on ,page #afg and #bnd line1 for #cb ounces1 read #fd ounces4 99 99 99 99 99 ,transcriber ,note ,minor typos may have been corrected4 ,images were moved so as to prevent splitting paragraphs4 ,all images were derived from materials made available on ,the ,internet ,archive and are placed in the ,public ,domain4