Studies on Physical Development (III)

Effect of the Potassium Iodide and 1-Phenyl-5-mercaptotetrazole upon the Development Rate and its Dependence on Complexing Agents

Abstract

In order to explain the role of the adsorption of complexing agents, silver complexes and developing agents on the silver nucleus, the effect of potassium iodide and 1-phenyl-5-mercaptotetrazole (PMT) upon the development rate of two different physical developers, which include thiocyanate and thiosulfate as complexing agents respectively, was investigated. Potassium iodide and PMT are known to be adsorbed on the silver nucleus under the formation of insoluble silver salts. N-2-(4-amino-N-ethyl-m-toluidino) ethyl-methanesulfonamide sesquisulf ate hydrate (Kodak CD-3), N-methyl-p-aminophenol hemisulfate (Metol) and hydroquinone were used as developing agents. The following results were observed: The effect of potassium iodide was largely dependent on the complexing agents. The developer including thiosulfate showed a very long induction period, especially in the hydroquinone developer. Potassium iodide accelerated the development in this period to reach the rate in the developer including thiocyanate. The development rate in the thiocyanate developer was hardly affected by the addition of potassium iodide. The mechanism f or this acceleration could be ref ered to the competitive adsorption of iodide with thiosulfate, which is restraining the development, on the surface of the silver nucleus. Iodide could be adsorbed more stronger than thiosulfate, removing it from that surface. The addition of PMT restrained not only the development of the thiosulfate developer but also that of the thiocyanate developer.