Some Effects of Gelatin on the Adsorption of Sensitizing Dyes on Silver Halide Grain Surfaces*

Abstract

AbstractStudies of the effect of the gelatin content of the suspension medium of silver halide emulsions show that sensitizing dyes added to such emulsions enter into adsorptive competition with a gelatin layer at the grain surface, which, at sufficiently high concentration of most sensitizers, appears to be completely displaced by the dye. Illustrative adsorption isotherms of representative carbo-cyanines, merocyanines, and other sensitizers as a function of the gelatin concentration of thesuspension medium are provided. Direct proof of the displacement of gelatin from the grain surface is obtained from nitrogen determinations on dyed and undyed grains.The isosteric heat of adsorption of dyes to emulsion grains, computed from the temperature coefficient of adsorption, is considerably higher in emulsions of low gelatin content than in normal emulsions. An interesting feature is the increase in the heat of adsorption found to accompany the onset of co-operative adsorption of one of the dyes studied.