Ciba-geigy Ag

Viktor Weiss

Mario Fryberg

Compounds of the formula ##STR1## in which R.sub.1, R.sub.2 and R.sub.3 independently of one another are hydrogen, alkyl or alkoxy and R.sub.2 additionally represents a radical of the formula ##STR2## in which R.sub.1 and R.sub.3 have the abovementioned meanings, R.sub.4 is unsubstituted or substituted phenoxy or unsubstituted or substituted amino and R.sub.5 is hydrogen or a radical of the formula ##STR3## in which R.sub.1, R.sub.3 and R.sub.4 have the abovementioned meanings and R.sub.2 ' has the same meanings as R.sub.1 and R.sub.3 are suitable development accelerators in the development of exposed, photographic materials containing silver halide. They accelerate the reduction of the exposed silver salt to silver and increase the speed of photographic material.

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Fribourg, Switzerland

Viktor Weiss