Photographic developing solution.

摘要

There is described a photographic developing solution which comprises at least one silver halide developing compound, an alkali metal sulphite, sufficient alkali to bring the pH within the range of 8 to 10 and as a buffer a compound of the general formula I:- B - Rn I wherein B is a phenol ring or an annelated phenol ring and R is a substituent group other than hydrogen and n is from 1 to 4 such that the compound has a pKa between 8 and 10 and is photographically inert. Useful compounds of formula I are phenols containing - SO3H or COOH substituent groups. Particularly useful are the p-substituted compounds. Another class of compounds of formula I which are particularly useful are naphthol compounds having one or two substituent groups R. Particularly preferred substituent groups R in the naphthol ring system are also -SO3H and -COOH. An especially useful naphthol compound is 1-naphthol-3,6-disulphonic acid which has a pKa of 8.2. Another useful naphthol compound is 1-naphthol-3-sulphonic acid which has a pKa of 8.6.