Growth of Potassium Chloride Crystals from Aqueous Solutions. I. The Effect of Lead Chloride

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Abstract
Single crystals of potassium chloride were grown from aqueous solutions under carefully controlled conditions of supersaturation, agitation, and impurity lead chloride concentration. The growth rate of the (100) face was determined. It was found that PbCl2 concentrations as low as 10−8 moles PbCl2/mole KCl decreased the rate of growth, and the retardation increased markedly with increasing PbCl2 concentration. The growth process changed from a layer type to a dendritic form over a small supersaturation range. Mass transfer rates of both KCl and PbCl2 from the solution to the crystal face were estimated and conditions delineated where each may be the rate‐controlling step. A mechanism is proposed to account for the formation of crystal clusters on the surface of KCl at slow stirring rates.