Process for Converting Silver Pictures into Platinum Pictures having Catalytic Power.

摘要

29,480. Bloxam, A. G., [Neue Photographische Akt.-Ges.]. Dec. 27. Printing; producing pictures which can be used as originals in reproduction by catalysis, as in Specifications No. 22,841, A.D. 1901, No. 27,896, A.D: 1902, and No. 13,920, A.D. 1903. A platinum picture obtained from a silver picture by treatment in a bath containing a platinum compound is not generally available, owing to the presence of substances interfering with the catalytic action of the platinum. A bath of ammonia removes the silver salt and imparts catalytic power, which however quickly deteriorates. According to the present process, a platinum picture, obtained by treating a silver picture with a bath containing alkali platinous chloride and a substance having an acid reaction in presence or absence of alkali chloride and hardening-agent, is treated either separately or simultaneously with a strong oxidizing-agent. and ammonia or an ammonium salt of a feeble acid. In cases in which the oxidizing-agent forms a precipitate which has a powerful catalytic action upon hydrogen peroxide, the precipitate is removed. For example, if potassium permanganate is used, the negative is treated with a solution of oxalic acid and alum.