Kinetics of Development by p-Phenylenediamine in Neutral and Moderately Alkaline Solutions

Abstract

p-Phenylenediamine is a moderately active developer for motion-picture positive-type emulsions in neutral solution in the presence of ascorbic acid. The ascorbic acid does not act as a direct developing agent at this low pH, but prevents the accumulation of development-retarding oxidation products. p-Phenylenediamine markedly increases the rate of solution of silver bromide in a potassium bromide or a bromide-sulphite solution. Development proceeds largely by solution-physical development in the p-phenylenediamine-sulphite solutions, but direct development is important in the action of the p-phenylenediamine-ascorbic acid solutions. The two types of solutions produce silver images which differ in colour and in the morphology of the silver grains. These differences can be correlated with differences in the relative importance of solution-physical development and of direct development in the over-all process. Adsorption of the sulphite ion by the silver bromide appears to have a significant effect on the kinetics of development by p-phenylenediamine solutions which contain sulphite.