The action of chromic acid on the sensitivity of solarized silver bromide plates

Abstract

1. 1. The reaction of chromic acid on the sensitivity of photographic emulsions is discussed and it was found to be of a complex nature. This can be analyzed into 1.1. (a) A very slow action on the silver halide itself. 1.2. (b) An action on the silver and on the silver sulfide of the sensitivity speck, with different reaction velocities. 1.3. (c) An action on the gelatin of partial hydrolysis and oxidation, forming and destroying at the same time a new sensitizer. 2. 2. This may explain the different effects of the chromic acid treatment on the sensitivity of different photographic emulsions. The abnormal action of a pure silver bromide emulsion after the chromic acid reaction in the overexposure region was investigated on this basis. 3. 3. In the overexposure region the desensitizing curves show irregularities that disappear if the curvesare derived from silver weights instead of densities. 4. 4. It was shown that these irregularities were caused by increasing silver weights in relation to decreasing densities in the first reversal of the solarization of the untreated emulsion. 5. 5. After the chromic acid treatment the grains of the emulsion develop in the usualway: with silver weights approximately proportional to the densities. 6. 6. An explanation of the sensitizing action of the chromic acid in the overexposure region was suggested on the basis of the concentration speck theory.