The Dictionary Of Photography

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Copper, Bromide of
• Copying
yellowish tears and masses, which are insoluble in water, slightly soluble in alcohol, more so in alcohol and camphor, freely soluble in chloroform, ether, and turpentine. It is used for making varnishes.
Copper, Bromide of (Ger., Kupferbromid; Fr., Bromure de cuivre; Ital., Bromuro di rame). CuBr., = 223.3. Synonym: Cupric Bromide. It occurs as a blackish powder, or in light-blue needle-like crystals, and is formed by dissolving cupric oxide in hydrobromic acid, evaporating and crystallising, also by mixing solutions of cupric sulphate and bromide of potash, evaporating, and separating the sulphate of potash. It is a deliquescent salt, and slightly soluble in alcohol. It is used as a first step in the copper method of intensification, in which case the insoluble cuprous bromide Cu2Br2 is formed in the film.
Copper, Chloride of (Ger., Kupferchlorid; Fr., Chlorure de cuivre; Ital., Cloruro di rame). CuCl2 = 134*3. Synonym : Cupric Chloride. Formed in a similar manner to the bromide, with hydrochloric acid, or by mixing a solution of cupric sulphate and calcium chloride, filtering from the precipitate of calcium sulphate, evaporating, and drying. It forms brilliant emerald-green needles, which are very deliquescent and easily soluble in alcohol. It is used as a reducer, and in Obernetter's copper process. There is also a lower chloride, cuprous chloride CuCl or Cu2C12 which is sometimes used as a convenient absorbent of chlorine in the preparation of chloroplatinite of potash.
Copper Ferricyanide, Toning with. See under Bromide Paper.
Copper, Sulphate of (Ger., Kupfersulfat, or Kupfervitriol; Fr., Sulfate de cuivre, or Vitriol bleu; Ital., Sulfato di rame). CuS04,5H20 = 249-3. Synonyms : Cupric Sulphate, Blue Cop-peras, Blue Vitriol. This is made by roasting copper pyrites with free access of air, lixiviation of the mass with water, evaporating, and crystallising. It occurs in beautiful blue crystals, some of very large size. Cupric sulphate has been used as an addition to the ferrous oxalate developer, its action being stated to be merely a retarding of oxidation of the ferrous sulphate.
Copying. This is an operation which is frequently necessary, and may be divided into three heads for convenience: (a) copying