| 摘要 |
1319721 Photographic silver image bleaching baths AGFA-GEVAERT AG 29 April 1971 [ 2 May 1970] 12073/71 Heading G2C A photographic silver bleaching bath contains an oxidising agent and a dicarboxylic acid of the formula: - COOH wherein n, m or p are 1,2 or 3 provided that n+m+p is less than or equal to 5; and R 1 , R 2 , R 3 or R 4 which may be the same or different, is H or alkyl having up to 5 carbon atoms and has a pH of from 5À0 to 6À5. The oxidizing agent is preferably a complex ferric salt. The acid may be glutanic acid, adipic acid or 2,2,4-trimethyladipic acid. The bath may contain sodium acetate or trisodium citrate which keep in solution aluminium salts, carried over from a preceding hardening bath, by complex formation. In Example 3 a stop-hardening bath is used before bleaching and after negative colour development which contains anhydrous sodium acetate, potash alum, boric acid and 1-(p-sulphophenyl)-3-methyl- 4-(d-ethylpropyl)-pyrazol-5-one as white coupler. The dicarboxylic acids are buffers which do not form aparingly soluble salts with trivalent metal ions (to prevent precipitation of inorganic hardeners) have little or no complex-forming action on Cr(III) and Al(III) ions (to prevent reversal of hardening of a layer of the material) and are resistant to the oxidizing agents in the bleaching bath. |
