NUCLEATION OF THIOUREA ADDUCT CRYSTALS WITH CYCLOHEXANE-METHYLCYCLOPENTANE SYSTEM

To study the homogeneous nucleation of thiourea adducts, the metastabl e zone widths for the thiourea adducts formed with guests of cyclohexa ne, methylcyclopentane (MCP) and their mixtures were determined. The i nfluence of moderate agitation rate and saturation temperature on the maximum allowable undercooling (i.e., metastable zone width) was studi ed. The metastable zone width is markedly affected by the cooling rate and the agitation rate. MCP in guests roles to retard the nucleation rate of cyclohexane-MCP-thiourea adducts by causing k(2) to decrease. The order of the nucleation in the nucleation process of thiourea addu cts is in the range between 3 and 6, and appears to be dependent on th e saturation temperature and the guest concentration. The nucleation r ate constant (i.e., frequency factor (k(2)/N-obs)) has shown to exclus ively depend on the concentration of guest and the temperature. The re tarding effect of MCP in the thiourea adduction was found to be caused by, not only the increase of surface energy, but the decrease of k(2) /N-obs.