The Dictionary Of Photography

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

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Gold, Chloride
Gold, Potassio-Chloride
chloric acid. It occurs native in conjunction with quartz and sand in various parts of the world. It is used for the preparation of chloride of gold, a convenient source being current coin. A
123^ grains, and contain 113
sovereign should weigh when new
grains of pure gold, the commercial value of this being 20s.; no charge being made for mintage or alloy.
Gold, Chloride (Ger., Goldchlorid, Chlorgold; Fr., Chlorure d'oro; Ital., Chloruro d'oro). Synonyms: Auric Chloride, Trichloride or Perchloride of Gold. AuCl3=303. A yellowish-brown crystalline mass, made by dissolving gold in aqua regia. Usually commercial chloride is obtained by solution as above and the evaporation of the acid liquid, in which case bright yellow crystals of AuCUHCl are obtained, from which it will be seen that one equivalent of hydrochloric acid is combined with it. Preferably the double neutral salts of gold and potassium, sodium or calcium, are used.
Gold, Hyposulphite (Ger., Natriumaurothiosulfat, Unter-schwefligsaures Goldoxydulnatron; Fr., Hyposulfile doubled'or et de sodium; Ital., Ipolsolfito d'oro e di sodio). Synonyms; Sel d'or, Fordos and Gelis' salt. Na2S20:.. Au2S203, 4H20. This salt was originally suggested for toning daguerreotypes, and later for albumenised paper, and more recently still for gelatino-chloride paper. It may be formed by gradually adding a neutral 2 per cent, solution of chloride of gold to a 6 per cent, solu-tion of hyposulphite of soda. To obtain it in crystals, mix the solution formed above with alcohol, when the salt will crystallise out in fine white needles.
Gold, Potassio-Chloride (Ger., Chlorgoldkalium; Fr., Chlorure double d'or et de potassium; Ital., Chloruro doppio d'oro e di potassio). AuCl3KCl +3H2O. The usual method of making this is to dissolve one part of pure gold in as small a quantity of aqua regia as possible, by the aid of heat. Evaporate gently, and then add 20 parts of distilled water, in which 0.51 parts of bicarbonate of potassium has been dissolved. Carbonic acid is given off, and the resulting solution should be evaporated to dryness. Lainer of Vienna has also suggested the following method for obtaining a stable and constant salt of gold, which can easily be prepared chemically pure and free
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