EXPLANATION OF THE DEVELOPMENT AND BLEACH ING PROCESS BY MEANS OF MIXED POTENTIAL-THEORY

The rate of both the photographic development and the bleaching does n ot usually depend on the redox potential estalished at the surface of silver/silver halide during the developing or bleach process, but rath er on the value of the so-called mixed current. At a rotated silver di sc electrode this mixed current as well as the corresponding mixed pot ential can easily be determined by recording the current-potential cur ves of the various redox couples. Thus, the mechanism and sometimes al so the kinetics of the development as well as the bleaching can be stu died by simulating these processes at a silver disc. This procedure al so explains the influence of both the kind and concentration of halide as well as the concentration of the reactants and the pH on the devel opment and bleach rate.