(472b) Understanding Metastable Zone Width without Nucleation Rate

Traditionally, the metastable zone width (MZW) in solution crystallization is thought to originate from the path-dependence of the steady-state nucleation rate of a solute. However, new experimental findings appear to go against this popular notion. In this work, we propose an alternate viewpoint to understand the MZW, and show that MZW may not necessarily be a function of the nucleation rate as conventionally understood.

Our work presents experimental data on the MZWs of various solutes and show that these data can be explained without invoking the concept of a nucleation rate. We use data from our own work as well as that from the recent literature. The applicability of the new concept of MZW to both evaporative and cooling crystallizations is shown. The stochastic view point of nucleation is contrasted against a more ‘deterministic’ view point of the classical nucleation theory. The pitfalls of obtaining nucleation kinetics from MZW experiments are discussed. Both induction time and MZW measurements are recommended as complementary experimental techniques to characterize the kinetics of nucleation in solution crystallization.