The Dictionary Of Photography

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

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Ammonium Hyposulphite           Ammonium Sulphocyanate
ammonia or carbonate of ammonia, the following being the method adopted by the British Pharmacopoeia.
Citric Acid ... ...... ... ... 12 parts.
Strong solution of ammonia          ... ... 11 ,,
Neutralise the acid with the ammonia, and add sufficient dis-tilled water to make 24 parts. This can be preserved as a stock solution for use in alkaline development. (See Development and Developers.) It has been employed in the preparation of gelatino-chloride emulsions, but its principal use is as a restrainer in development of chloride emulsion plates.
Ammonium Hyposulphite. (NH4),S203+5H20, has been recommended as a fixing agent in place of the sodium salt, but it is much more costly.
Ammonium Iodide (Ger., Jodammonium; Fr.,Iodure d'am-monium; Ital., Ioduro d'ammonio). NH4I = 145. Used for making Iodised Collodion (q.v.). Solubility : 4 in 3 of water, 1 in 4 of alcohol, 1 in 20 of ether, and 1 in 20 of alcohol and ether.
Ammonium Oxalate (Ger., Ammoniumoxalat; Fr., Oxalate d'amma?ii?tm; Ital., Ossalato di ammoniacd). (NH4)2C204 = 124. Sometimes used for preparing paper for platinotype printing. Solubility: 1 in 3 of water; insoluble in alcohol
Ammonium Sulphide (Ger., Ammoniumsulftd, or, Schwefel-ammonium; Fr., Sulfure d'ammoniaque ; Ital., Solfuro d'ammoniacd). (NH4)2S = 68. Synonym: Sulphuret of ammonia. Prepared by passing sulphuretted hydrogen through ammonia solution until the gas ceases to be absorbed. It is used in Intensification (q.v.) to blacken the white image obtained by bleaching the negative with mercuric chloride. A caution is necessary as to the use and storage of this in any room where sensitive materials of any kind are kept, as the vapours may act on the sensitive surface. If an amount of ammonia equal to that originally used is added after saturation with sulphuretted hydro-gen, ammonium sulphydrate is formed; this being often preferred.
Ammonium Sulphocyanate (Ger., Rhodanammonium; Fr., Sulfocyanure d'ammonium; Ital., Rodanuro, or, Solfocianuro d'ammonio). NH4CNS = 76. Used for toning gelatino-chloride printing-out papers, and has also been recommended as a fixing agent instead of hypo, but from its comparatively high price,
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