Mechanisms of Particle Growth in AgBr Hydrosols

1977 Journal of The Society of Photographic Science and Technology of Japan  
Exchange of bromide ions between solid and solution during aging of a silver bromide hydrosol was investigated by use of radioactive 82Br-. The exchange was found to proceed in the same way as that of silver chloride via two essential steps; the first an instantaneous surface exchange, and the second a relatively slow process due to recrystallization (Ostwald ripening). The thickness of the surface layer in equilibrium with solution was calculated to be 3.2 atmic layers. Also, drastic contact
more » ... crystallization was observed in the AgBr hydrosol. About six times as much amount of 4-hydroxy-6-methyl-1, 3, 3a, 7-tetraazaindene per unit surface for AgBr as for AgCI were necessary for stopping the recrystallization and the exchange of halide ions. From the relationship between the change in the degree of exchange and the change in average particle volume were clearly distinguished the mechanisms of particle growth in silver bromide hydrosols, such as Ostwald ripening, contact recrystallization, and coagulation. When Pb++ ions were added to AgBr hydrosol, the particle underwent coagulation followed by contact recrystallization, while addition of ammonia gave rise only to acceleration of Ostwald ripening. These conclusions were led from the analysis of the curves of the degree of exchange versus average particle volume. Namely, the curves for the control and the sol with ammonia entirely coincided with each other, while the curve of the sol with Pb++ was greatly separated downward from them.
doi:10.11454/photogrst1964.40.15 fatcat:r7vizmmnoneiloorvxkspnju3m