| http://www.w3.org/ns/prov#value | - It has now been found that darkening of the developer and formation of a black silver mud can be avoided by adding to the developer solution derivatives of Z-mercapto- 1,3,4-thiadiazoles of the general formulae: H's-( i l-X131 HS-(J -X-Jiz-X-i] i l-SH (III) NN NN Hsii-(oEnn-ii (l-SH s s wherein X is a bivalent radical such as the S (thio) or =NH (imino), R represents a radical such as alkyl with
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