Adsorption of 4–Hydroxy–6–methyl–l,3,3a–tetrazaindene in Aqueous Silver Halide Dispersions

Abstract

AbstractAdsorption determinations of the title compound (TAI) al 25°C in aqueous gelatin dispersions of cubic AgCI and cubic or octahedral AgBr conlirm that its adsorption is favoured by high pH and low pAg. This behaviour is interpreted in terms of competition for surface sites among halide ion, TAP (the azaindene’s anionic deprotonation product) and TAIH (the uncharged product). The resulting competitive adsorption model was used to calculate TAI- surface coverages at silver halide surfaces. These calculated coverages were confirmed experimentally at various pH and pAg values. The adsorption constants and limiting site areas of TAIH, TAI and halide ions are compared. TAI- is more strongly bound to cubic AgCI than to cubic AgBr, and, relative to TAI-, the adsorption nf TAIH is negligible at pH >4. At saturation, the surface occupancy by TAP on octahedral AgBr is about twice that on cubic AgBr. with a limiting site area of about 0.25 nm2/TAI- al octahedral AgBr and cubic AgCI surfaces. These data are cons...