Transitions in Crystal Habit in Silver Bromide Emulsions

Abstract

AbstractA series of AgBr emulsions has been prepared under controlled pAg conditions from a monodisperse “seed” emulsion, concentrating in those pAg regions where there is a transition from one crystal habit to another. The transition point between cubic and octahedral forms is defined as that tetradecahedron which has equal surface areas of (200) and (111) faces. The second transition point is that pag where precipitating AgBr is diverted to the formation of twinned crystal under the conditions of the experiment. A correlation was made between the observed transition points and the concentrations of the silver complexes in solution.The effect of crystal habit on sulphur sensitization was studied lIsing a set of cubic, tetradecahedral and octahedral emulsions having the same average grain volumes. The tetradecahedral emulsions were found to be intermediate in their behaviour between cubes and octahedra. The thiosulphate additions required for maximum speed were in the order: octahedral < tetradecahedralec...