The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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Silver Acetate                                          Silver Bromide
Silver Acetate (Ger., Silberacetat, Essigsaures Silberoxyd). AgC2H302 = 167. Is obtained in white crystals .by mixing silver nitrate with a soluble acetate. The crystals are soluble, 1 in 100 parts of water.
Silver Albuminate (Ger., Silber Albuminat; Fr., Albuminate d Argent; ltal., Albu?ninato d'Argento). The white precipitate obtained by adding nitrate of silver in solution to albumen in the dark is thus termed. It is a complex compound of oxide of silver and albumen, and is reduced to a red sub-compound by the action of light. It is this reaction which occurs when printing on sensitised albumenised paper.
Silver, Ammonio-Nitrate of (Ger., Salpeiersdures Silber-oxyd-ammoniak; Fr., Nitrate ammoniaea I d'argent). 2 NH3AgN03. The pure salt can be obtained by exposing powdered nitrate of silver to ammonia gas, combination taking place very rapidly, and with evolution of sufficient heat to fuse the resulting com-pound, which contains 22*5 per cent, of ammonia, NH3, and 77-5 per cent, of silver nitrate, AgN03. Ammonio-nitrate of silver is used for sensitising plain salted paper. It cannot be used for the same purpose with albumenised paper, as the albumen would be dissolved ; it is also used in making emulsions. It may also be prepared by dissolving silver oxide in solution of ammonium-nitrate, or adding ammonia drop by drop to solution of silver nitrate till the precipitate first formed is redissolved. A solution containing less ammonia may be obtained hy dividing the solu-tion of silver nitrate into two equal parts, to the one adding sufficient ammonia to obtain a clear solution, and then adding the other half of the silver nitrate solution.
Silver Bromide (Ger., Bromsilber; Fr., Bromnre d'argent; Ital., Bromuro d'argento). AgBr = 188. Can be prepared by direct union between the elements, as in the Daguerreotype process, or by double decomposition between nitrate of silver and any soluble bromide, as in dry-plate processes: - ■
AgN03 + KBr = AgBr + KN03 Silver            Potassium _ Silver            Potassium
nitrate            bromide           bromide            nitrate.
Or it may be prepared by treating carbonate or oxide of silver with hydrobromic acid. Bromide of silver is darkened to a