Black and white development process in which the developer bath at pH 8, contains 1:2- ethylenesulphate, 1-methyl-1:2-ethylenesulphite, 1:2-dimethyl -1:2-ethylenesulphite, 1:3-propylenesulphite or dimethyl sulphate. Pref. developers are hydroquinone or its chloro or bromo deriv. N-methyl-p-aminophenolsulphate or 1-phenyl-3-pyrazolidone and their derivs. Pref. alkalis for the bath are quaternary ammonium hydroxides metal alkali carbonates, borates or hydroxides, and hydroxyalkylamines. The bath opt. contains an Ag halide solvent and a hardener partic. an aldehyde. Partic. for use in non-viscous concentrated soln which are diluted before use.
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