PURIFICATION OF ORGANIC-SOLID SOLUTIONS BY MELT CRYSTALLIZATION - COMPARISON BETWEEN LAYER AND SUSPENSION CRYSTALLIZATION

In order to compare the degrees and rates of purification achieved by layer and suspension melt crystallization operations, purification by ''sweating'' of naphthalene-benzothiophene solid solution crystals was carried out after they were formed either on a cold surface (layer cr ystallization) or in supercooled melts (suspension crystallization). T he purification rate coefficients obtained for the suspension system c rystals were found to always be larger than those for the layer system , furthermore, the amount of impurities unable to be removed by ''swea ting'' from the layer was higher than that from the particles. These t wo facts lead to the conclusion that the overall efficiency for the pu rification by sweating is higher for the suspension crystallization th an the layer one.