IS PHOTOGRAPHIC DEVELOPMENT AN AUTOCATALYTIC PROCESS

Photographic development is commonly assumed to be autocatalytic due t o the growing developed silver surface. the parallel development of gr ains is shown to increase the silver mass as a simple linear function of time. Its constant term corresponds to the initial soaking period. After the smaller emulsion grains become completely developed, the lin earity starts to be distorted. Its distortions, caused by using a dens ity scale instead of a silver mass scale, by high polydispersion of mi crocrystals and thickness of emulsion layer, have led to the wrong con clusion of first-order development kinetics. The granular development is shown to tend also to a linear kinetics with a larger constant depe nding on the replacement rate of pre-adsorbed bromide by developing sp ecies from a catalytic surface. The first-order expression seems forma lly closer to granular kinetics that is influenced by some deviations in the exponential size distribution of latent image centres. Evidence for the constant growth rate of silver filaments, the particular and permanent activity of their ends is discussed. The latent image nanocl usters, that can be stabilized by some interactions typical to ultradi sperse metals in statu nascendi and polymers, suggest themselves to be the catalytic sites of particular and permanent structure on the surf ace of developing silver particles.