| 摘要 |
736,881. Photographic processes. AGFA AKT.-GES. FUR PHOTOFABRIKATION. Feb. 17, 1953 [Feb. 19, 1952], No. 4442/53. Class 98 (2). Stains formed on photographic colour images by the reaction of any phenolic hydroxy groups present in the image dyestuff with heavy metals (for example iron) present in the processing solutions or wash water, are removed by treatment with an aqueous solution of a polyphosphoric acid or a complex-forming organic polycarboxylic acid or a water-soluble salt thereof. Such treatment also removes any stains of Prussian blue formed by bleaching coloured images contaminated with rust particles in a potassium ferricyanide solution. Suitable compounds, which have a greater affinity for the heavy metals than the phenolic hydroxy groups are polyphosphoric acids, tartaric, citric, diglycollic, and thiodiglycollic acids and polycarboxylic acids containing an amino group such as ethylene-bis-(imino-diacetic acid), trimethylamine-α,α<SP>1</SP>,α<SP>11</SP>-tricarboxylic acid, 1,2-diamino-4-methylcyclohexane-N, N<SP>1</SP>-tetra-acetic acid, propylene-1,2-diaminotetra-acetic acid, di-isopropylene diamino-tetraacetic acid and 1,3-diamino-propane-2-ol-tetraacetic acid. The water-soluble salts of any of these acids may be used, in particular, sodium hexametaphosphate. Specification 474,082, [Group III], is referred to. |
