Predicting the Effect of Impurity Adsorption on Crystal Morphology

Phenyl salicylate (salol) crystals were grown from mixtures of varying composition. The analysis of growth rates revealed changes in growth rate similar to observations made by other authors. Considering relative growth rates to characterize crystal morphology, the latter was also found to depend upon impurity concentration. On the basis of an empirical approach proposed by Davey and Mullin, a new model to predict crystal morphology that depends upon the concentration of impurities in the bulk liquid was developed. The concept of site-specific adsorption on crystal surfaces was implemented in a procedure to simulate adsorption with molecular modeling methods. Data obtained from these simulations were applied to the newly developed model to predict the crystal morphology of salol in the presence of three different impurities. The results of the experimental study and the prediction revealed small deviations, but the general trend is clearly reproduced.