The photographic news

• Bandzählung: 12.1868
• Erscheinungsdatum: 1868
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-186800009
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• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

JANUARY 17, 1868.] THE PHOTOGRAPHIC NEWS. 31 the carbonate or sulphate of ammonia. From theoretical con siderations, this should, of all the alkaline hyposulphites, prove to be the best fixing salt, since it unites within itself the two conditions I adverted to when speaking of the addition of carbonate of ammonia to the ordinary fixing bath ; and from my limited experience of the hyposulphite of ammonia, made in small quantity and by the above indirect processes, 1 consider that its advantages in use, if substantiated by further investigation, would justify the manufacturer turning his attention to the substitution of ammonia for soda in preparing a commercial article. 1'110 facility of crystallization, permanence, and other properties of the new salt will have to be determined, and if it can be introduced cheaply into commerce, it is likely to prove a great boon tophotogiaphers. Using a bath of hyposulphite of ammonia subsequently to the ordinary fixing solution, I have succeeded in removing all but the last traces of silver from the white portions of albumen prints without injuring the biilliancy of tone for which these photographs are dis tinguished. I must, however, leave to a future occasion a fuller account of my experiments in this direction. Woolwich, Jan. 10th, 1808. RESUSCITATION OF THE OLD TONING AND FIXING SOLUTION, AxD the Treatment of this Solution when Exhausted or Saturated. BY PROFESSOR JOHN TOWLET, M.D.* WASHINO THE PRINTS. This is al ways an important operation, and must bo thorough. Wo need not dwell upon this part; all know how to wash their prints, and have their own way and notions of doing the work : do it thoroughly. Finally, wash or soak them in a solution of common salt, which removes the last traces of the hyposulphite of soda; wash them again in fresh water, and then dry them. So prepared, the silver picture is more brilliant and vigorous than when toned according to our more modern plan; it remains to be seen whether it is equally permanent. Numerous yellow prints toned in this manner some years ago attest to the contrary ; but we believe that in those days the same care in washing was not observed as is now observed ; for several prints before us, that were toned in the mixed bath then, are still as fresh and white in the whites as the best prints now when taken from the wash-tub. If the fact of permanency can be proved to be a fact, we have no hesitation then in pronouncing the mixed toning and fixing bath as the easiest, the most econo mical, and the most reasonable of all existing toning and fixing methods. DISPOSITION OP THE EXHAUSTED SOLUTION. Wo do not yet know any certain criterion or test by which the solution can be easily shown to b; saturated with chloride of silver ; our plan is to reject the bath the moment it begins to precipitate a deposit; this takes place after it has been in continual operation for about three or four days ; that is, after four or five hundred card-pictures have been toned in about a quart of it. Even at this stage it will continue to tone and fix ; but it is somewhat doubtful whe ther it is advisable to trust it much further. The question, then, arises, What shall we do with the solution now? There are several modes of treating it in order to extract the silver from it. First method.—Throw into the solution a quantity of gra nulated zinc; that is, zinc which, when melted, has been poured from a height of three or four feet into a pail of water. By this process the zinc is broken up into small, irregular lumps, suitable for this purpose. Leave the metal in for several days, and stir the solution several times during this interim. The zinc in this operation takes place both of the silver and gold in the solution, and precipitates them— * Continued from p. 22. the former as a fine silver-gray powder, and the latter as a black and a red powder. When the convenient time comes, pour the solution from the metals ; add water to the latter, and wash the remaining pieces of zinc well, and then remove them back again to the same solution as before, in order to see that all of the noble metals have been removed. Wash the mixed powder first in dilute sulphuric acid, and after wards in several changes of water, and then dry it. Place the dry mass or powder in a clean iron ladle, and heat it in an open fire-place to a low redness, and maintain it at tins temperature. In this way any salt of silver, such as the sulphide, sulphate, &c., will be reduced to the state of oxide. Boil the powder which has been thus treated in about its weight of nitric acid, diluted with an equal quantity of water, until all is dissolved excepting a small portion of a reddish coloured powder; this remaining powder is gold, which may be dissolved in a mixture of two parts of hydro chloric and one of nitric acid. The former solution is next evaporated to dryness in a porcelain or glass dish ; the dry salt is nitrate of silver. We sometimes avoid the trouble of oxidizing the silver salts, and boil the gray mass at once in nitric acid ; but in this way there is some loss. Second method.—Filter the old bath and employ it for gal vanic plating; it is in its present form in an excellent con dition for coating copper and brass instruments with pure silver, either with or without the aid of the galvanic battery. It is very possible that you may find a market for this residual substance the moment it is known to be available for the purpose just indicated. Third method.—Add a quantity of sulphide of potassium (liver of sulphur) to the old bath solution ; the silver in this way is precipitated as sulphide, which may be sold as such to the refiner. N.B.—The silver, which has been precipitated both from the old hyposulphite bath and from moist chloride of silver, is sometimes in a very curious condition—its allotropic con dition, perhaps. This condition is shown by its difficult solubility in nitric acid. In consequence of this, we prefer mixing the dry metallic powder with its weight of carbonate of soda, and then fusing it in a Hessian crucible. The button of metal thus produced is now in a very soluble con dition when submitted to the action of nitric acid—the gold remains undissolved as a black powder, and may, after separation from the fluid nitrate of silver, be washed first, and then dissolved in nitro-hydrochloric acid. Hroceedings of Sucieties. South London Photooraphic' Society. The usual Monthly Meeting was held in the City of London College on the evening of Thursday, January 9th, Mr. Sebas tian Davis in the chair. After the minutes of a previous mooting had boon road and confirmed, Mr. J. R. Johnson road a paper on Securing Clouds in Land scape Negatives (seo p. 28). Mr. Johnson exhibited a large number of very fine prints taken with the pantascopic camera, amongst which wore many of Braun’s views of Swiss scenery on plates 20 inches by 9 inches, many possessing very fine clouds, and all having graduated and atmospheric looking skies. Mr. Wharton Simpson said that Mr. Johnson’s remarks for the most part carrie conviction with them, and that he had stated so much of truth that it was difficult to attempt to discuss or controvert anything ha had said. All landscape photo graphers would doubtless desire to secure in one negative tho clouds present in the sky as well as tho landscape proper, and the means suggested by Mr. Johnson would often be efficient in enabling the photographer to secure such effects. But there was one point which, although it had been touched upon at the last meeting, had not received so much attention, ho thought, as it deserved. Mr. Johnson had referred to tho importance of securing, nt one operation, tho clouds and the