The Dictionary Of Photography

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

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Silver Chromate                                              Silver Iodide
carbon, but is immediately reduced by heating in a current of nascent hydrogen. Zinc, iron, and copper reduce the chloride, when moistened with an acid, to a metallic state; whilst when heated with the carbonates or hydrates of sodium and potassium or calcium, the chlorine unites with the alkali, pure silver being set free. It is soluble in solutions of the same salts as the bromide, and also in ammonia - a double salt, ammonio-chloride of silver, being formed. It is used for making lantern-plate emulsions, gelatino-chloride printing-out papers, and is the sensitive salt in albumen paper.
Silver Chromate (Ger., Chromsdures Silberoxyd; Fr., Chromati d'argent; Ital., Cromato d'argento). Ag2Cr04. An orange-red precipitate, formed by mixing chromate or bichromate of potassium with silver nitrate. It was suggested by Biny for emulsion making, and by Burton as an admixture with bromide emulsion to stop halation.
Silver Citrate (Ger., Silbercitrat, Citronensaures Silberoxyd; Fr., Citrated'argent/Ital., Citrate d'argento). AgC6H507 = 297. This can be obtained in small quantities by adding citric acid to silver nitrate, but more easily by double decomposition of a soluble citrate and silver nitrate. It forms white crystals, which are soluble in water. It was suggested by Monckhoven for gelatino-bromide emulsion, but its chief use is in the gelatino-chloride printing-out papers.
Silver Fluoride (Ger., Fluorsilber; Fr., Fluorure d'argent; Ital., Fluoruro d'argento). AgF = 127. This salt is formed by solution of silver oxide or carbonate in hydrofluoric acid, not by double decomposition of silver nitrate and a soluble fluoride. It is fairly stable in light, and soluble in water. It has been suggested for use in emulsions for development and printing-out, but has not come into general practice.
Silver Iodide (Ger., fodsilber, Silberiodid; Fr., lodure d'argent; Ital., loduro d'argento). Agl = 235. This salt can be formed in an analogous manner to the chloride, either by direct union or double decomposition, using iodine and iodide instead of chlorine and chloride. When prepared by precipitation from a solution of an alkaline iodide with nitrate of sliver, the alkaline iodide being in excess, a white precipitate is caused, which is not
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