GB754419A - Aromatic nitroso compounds as silver oxidizing agents - Google Patents

Abstract

754,419. Photographic bleaching compositions. GENERAL ANILINE & FILM CORPORATION. Nov. 16, 1954 [March 19, 1954], No. 33187/54..Class 98 (2). A photographic silver bleaching composition comprises an aqueous solution of an acid, an alkali metal bromide and a water-soluble tertiary amino-p-nitroso compound of the benzene series, wherein the substituents on the tertiary nitrogen atom are aliphatic radicals containing not more than four carbon atoms or aromatic radicals of the benzene series. The tertiary amino substituents include alkyl, hydroxyalkyl, carboxyalkyl, sulphoalkyl, phenyl, toluyl, sulphophenyl or carboxyphenyl groups. The nitroso compound may bear other substituents in the benzene ring to which the nitroso group is attached, such as hydroxy, alkyl, alkylsulphamyl, arylsulphamyl, alkoxy, or hydroxyalkyl groups. A number of suitable compounds are specified. The nitroso compounds may be made by treating the t.-amino compounds in acid solution with aqueous sodium nitrite, and the resulting solution may be used directly as a bleach bath after the addition of an alkali metal bromide. The preferred acid is hydrochloric acid. The bleaching baths may be used in the same way and at the same point in the processing of photographic film, particularly colour film, as the usual ferricyanide baths. U.S.A. Specification 2,625,477 is referred to.