Number and Size of AgBr Crystals as a Function of Addition Rate


Number and Size of AgBr Crystals as a Function of Addition Rate – A Theoretical and Experimental Review

Ingo H. Leubner, Journal of Imaging Science and Technology, 37(3): 168-271 (1993)

This publication derives in detail the dependence of crystal number on reaction addition rate. It also corrects previous erroneous experimental data points.

The dependence of the number of crystals formed (Z) as a function of molar addition rate (R) was reviewed with regard to the BNG theory of crystal nucleation. The precipitation of silver bromide was used as a model to test the predictions.

The theory predicts that the number of crystals formed under diffusion –controlled growth and homogeneous precipitation conditions depends on the molar addition rate, so that logZ increases linearly with logR, with a slope equal or less than 1.0. Previous precipitations of AgBr at 70C and pAg7.1 were repeated and extended. An erroneous data point that previously caused a slope of 0.84 was corrected. The extended data range from 0.020 to 128 mmol/min addition rate of AgNO3 gave a slope of 1.01 with a standard deviation of 0.001, and a correlation coefficient of 0.990. The crystal size ranged from 0.121 to 0.132 µm, with an average of 0.129 µm (std. Dev. 0.004 µm).

References are cited where lower lofZ/logR slopes than 1.0 were observed, in agreement with the model. The author knows of no reported slopes significantly greater than 1.0.