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THE PHOTOGRAPHIC NEWS Vol. VII. No. 258.—August 14,1863. CONTENTS. arc the sol- Copyright in Works of Fine Art Recent Patents PAGE . 392 393 refuse to give satisfactory results. Various causes alleged. Some attribute it to the use of bromides in collodion; others, to the uses of methylated spirits as Correspondence — Foreign Science — An English Amateu’s Glance at French Photography — Cumulative Effects in Photography—Formula for the Determination of the Com parative Duration of Exposure, &c 393 Photographic Notes and Queries—Glass for Dark Rooms—Mea suring the Angle of Photographs 395 Talk in the Studio 396 To Correspondents 396 Photographs Registered during the past Week 306 vents of pyroxyline ; others to the use of ordinary alcohol distilled from potato, malt, &c., and containing essential oils; others, to organic additions to the collodion ; others, to impure and unsuitable iodizing salts; others,to the prevalence of adulterated or impure nitrate of silver. All these causes may, occasionally, be chargeable, but there is another, which, also, possibly has more influence than is recognized. We allude to the enormous amount of work the nitrate bath frequently gets, to what it used to do a few years ago. Since the introduction of card- portraits, we imagine that in many portrait establishments ten-fold more negatives are produced now than were a few years ago ; and the nitrate bath gets a proportionate increase of work in the time. Without adverting further at present to these causes which are largely beyond the control of the photographer, it be comes an important question with him, therefore, to consider, first, how to best keep his bath in order so as to secure constant conditions, and next how to rectify it when out of order. We shall devote a few lines to each of these subjects. How to Make and Keep the Bath in order. — Make the bath of a strength of thirty grains to the ounce for summer, and thirty-five grains, or forty, to the ounce for winter use. Iodize it, by leaving a large coated plate in for a few hours. If it work foggy neutralize with freshly precipitated oxide of silver, or carbonate of soda, and sun for a few hours. Then filter and try again, working it as nearly neutral as possible, adding, if acid be necessary, the smallest trace of nitric acid. Wc will now suppose the bath is in good working order, and the object is to keep it so, or what is equivalent to secure the greatest possible constancy of good conditions. We now ask the careful attention of our readers for a moment. We have already said that the nitrate bath is beginning to change its constitution from the moment it is brought into use. No care can prevent the accumulation of foreign matter in the bath, but the greater portion of this would be comparatively inert in determining the character of the sensitive film of iodide and bromide of silver, if we could remove it from the free nitrate on. and in the film which is reduced in developing. The affinities exist between iodine and bromine and the silver in the solution, and these elements will combine, forming iodide and bromide of silver, regardless of the foreign matter which may be present. It is true that foreign matter present may become to some ex tent entangled in the film with these elements as they com bine, the more so if the idea be accepted of the formation of sensitive double salts of iodide and nitrate of silver and bromide, and nitrate of silver, but it is to the presence of the foreign matter in the free nitrate on the plate that irregular reduction, causing stains, fogs, pinholes, &c., &c., is chiefly due. I How are these impurities in the free nitrate to be got rid ON THE MANAGEMENT OF THE NITRATE BATH. There is no preparation used by a photographer of more vital importance than the nitrate of silver bath, and yet none in regard to the condition of which he possesses so little certainty. By care he can secure collodion of constant quality ; or at the worst he can be certain that the stock in use for a given period, say a day or a week, or months, conti nues unchanged. In his developing solution he can secure just what conditions he may please, unvarying in all respects if he desire. But in regard to the nitrate bath, none of these things are possible ; it is continually change- ing ; it is not the same bath for two consecutive plates. In using the collodion and developer a definite portion of each is consumed, and what remains behind continues of the same quality. The nitrate bath is continually being deprived of of some of its elements and receiving an accession of others; there is a constant interchange of particles. . It is com posed, to begin with, of water, nitric acid, silver, iodine, and perhaps a trace of bromine. On the immersion of every plate it is deprived of a portion of its water and silver in uncertain quantities. It is supplied in place of the silver with some other base, or a mixture of bases, it may be cad mium, potassium, ammonium, lithium, magnesium, calcium, zinc, and occasionally a trace of iron. It receives besides continued accessions of ether and alcohol and probably traces of other organic matter. It also probably continually gains accession of some traces of iodine and bromine, and there is a gradual accumulation of iodo-nitrate of silver. Besides the decompositions and recompositions which are intended to take place, and which are anticipated in the order of things, there are others not always intended which are uncertain and beyond control, such as arise from the liberation of nitric acid and oxygen by free iodine in the collodion, and from the reactions between ether and alcohol and free acid. There may be the train, of complications arising from the addition of acetates. I here may be occasionally other de compositions arising from unknown empirical additions to increase the sensitiveness or density of collodion, or the use of impure methylic solvents in its manufacture. When all these considerations are remembered, and that the changes produced never remain for two plates the same, it is scarcely surprising that, nitrate baths occasionally “ get out of order.” It happens fortunately for photography and photographers t lat a nitrate bath of originally sound and healthy consti- tu ion, is very hardy. If made originally from pure ma- en1a S: and worked with ordinary care and moderately pure colod ion, it will continue parting with much it originally Fution without receiving much foreign addition to its consti- “ Eiaasw* or being attacleed with sick- plaints from good photoptasthere have been frequent com- of the rapidity with whichth<ers,,amateur and professional h their baths get out of order and PAGE On the Management of the Nitrate Bath 385 Reproduction and Copyright 386 Photographs in Printing Ink 387 Photographic Chemicals 387 An Attempt to Secure Certainty in Gold Toning. By a Photo grapher’s Assistant 388 Photergimetry. By Sig. Garneri, of Turin"'...’. 389 On Malic and Maleic Acids as New Isomeric Bodies. By II. Kammerer 390 On the Composition of the Photographic Picture. By Eugene Sahler 390 Boings of the Sunbeam 390