An investigation of solute nucleation in levitated solution droplets

Abstract An experimental technique that involves the use of a single micrometer-sized particle suspended electrodynamically in a laser beam has been developed and shown to have great potential for studying crystal nucleation from aqueous electrolyte solutions. Critical supersaturations required for the onset of solute crystallization have been determined for the NaClH 2 O and the (NH 4 ) 2 SO 4 H 2 O systems. The data so obtained are used, in conjunction with nucleation theory and electrolyte solution thermodynamics, to deduce the interfacial free energy, shape, and size of the critical nucleus. For both systems, the critical nucleus is a compact microcrystal composed of only a few unit cells.