GROWTH-RATE ENHANCEMENT OF POTASH ALUM CRYSTALS BY MICROCRYSTALS

During the steady growth of a single crystal of potash alum fixed in a clear supersaturated solution, secondary nucleation was intentionally induced by adding ground potash alum crystals and the resulting chang es in the growth rate and the solution concentration were measured. Th e growth rates after the nucleation were found to abruptly increase by a factor of up to 3, and to gradually return to the steady growth rat es or to some constant values. At the same time, the solution concentr ation started to decrease at the moment of the nucleation. As a measur e of the growth rate increase the enhancement coefficient, epsilon(0), was introduced which was defined as the ratio of the growth rates in the presence to the absence of microcrystals at the same supersaturati on. The values of epsilon(0) were found to be almost independent of th e growth rate in the absence of microcrystals, i.e. the solution super saturation.