The Dictionary Of Photography

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Silver Carbonate
Silver Chloride
tawny grey by the prolonged action of light, with evolution of bromine; but by short exposures, as in the camera, it is said to be reduced to a sub-bromide, or, as Carey Lea calls it, a photo-bromide of silver. Sub-bromide of silver in this stage is pre-cisely the same in physical appearance as the bromide; but it is more easily reducible by certain salts, which constitutes the process of Development (q.v.). Bromide of silver is practically insoluble in water, alcohol, and ether, but soluble in solution of alkaline hyposulphites, cyanides, sulpho-cyanides, ammonia (about I : iooo), and saturated solutions of most chlorides, bromides, and iodides. Silver bromide is the usual sensitive salt in emulsions, either alone or combined with iodide and chloride.
Silver Carbonate (Ger., Sz'lbercarbonat, Kohlens&ures Silber; Fr., Carbonate d'argent; Ital., Carbanato d'argento) Ag2C03 = 276. This can be obtained as a yellowish precipitate by mixing silver nitrate and sodium carbonate solutions. It blackens in light, and is partly decomposed by boiling with water into oxide. It is insoluble in water, alcohol, and ether, but is soluble in all the solvents of the haloid salts of silver. It has been used in emulsion making, either for forming bromide, by treatment with hydrobromic acid, or in the form of ammonio-carbonate of silver, by dissolving the carbonate in ammonia. It has also been suggested by Burton and others for gelatino-chloride printing-out papers.
Silver Chloride (Ger., Chlorsilber, Silberchlorid; Fr., Chlorure d'argent; Ital., Chloruro d'argento). AgCl = 143*5. Can be obtained by direct union between the elements, or by double decomposition with nitrate of silver with a soluble chloride,
AgNOa + NaCl = AgCl + NaNOa ; or by adding hydrochloric acid to silver nitrate, AgN03 + HC1 = AgCl + HN03.
It also occurs as a native ore, called horn silver, from its general appearance. On exposure to light when absolutely pure or dry no change takes place; but with the smallest trace of organic matter or water it passes from white through varying shades of purple to black, chlorine being disengaged, and a complex body now definitely stated to be a mixture of chloride (AgCl), oxy-chloride (AgCIO), and metallic silver (Ag) resulting. It melts at about 2600 F. and is not decomposed when heated with
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