CRYSTALLIZATION KINETICS AND INTERFACIAL-TENSIONS OF CYANAZINE PRECIPITATED FROM AQUEOUS-ETHANOL SOLUTIONS

A desirable move away from hydrocarbon-based emulsifiable herbicide co ncentrates towards aqueous dispersible concentrates requires understan ding and control of the crystal precipitation process. In this study, induction periods of the organic herbicide cyanazine (Blandex(TM)) in aqueous ethanol solutions are measured as a function of supersaturatio n and analysed to infer the mechanism of crystallization and the inter facial tension. The data are consistent with models of primary nucleat ion followed by either polynuclear or diffusion-controlled growth resp ectively with inferred interfacial tensions comparable to those determ ined from independent solid-liquid contact angle measurements. Primary nucleation is found to be either heterogeneous or homogeneous dependi ng on the supersaturation range (low and high respectively).