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This paper is a continuation of previously reported studies made in this laboratory on the adsorption of foreign substances by growing crystals (

The previous papers1 2in this series of investigations have shown that the growth ratios of potassium and ammonium alum crystals are greatly modified when grown in the presence of dyes and other foreign substances. Thus potassium alum, when grown in the presence of diamine sky blue develops into perfect cubes having no octahedral faces. The cube faces alone are colored and the growth ratio [ioo]/[iii] undergoes a change from 1.61 to o.o in a dye concentration of 0.1%.These effects have been accounted for on the basis of (i) the residual valency force fields of the crystal planes; (2) the interionic distances within the faces; and (3) the presence and distribution of polar groups in the adsorbed material.

The present work is a continuation of the study of adsorption processes a t soIutioncrystal interfaces. I t consists of an investigation of the adsorption of dyes and gelatin by the various faces of potassium alum. The growth ratios of this alum were measured both in the presence and absence of the dyes and gelatin. I t was found that Bismarck Brown and Diamine Sky Blue greatly affected the growth rates of the cube faces and also modified the crystal habit. This effect is explained on the basis of the ionic structure of the faces and the presence of polar groups in the dyes. The growth ratio Vlm/VII1 for pure potassium alum was found to be 1.61.