Nucleation monitoring in cooling crystallization with a quartz crystal oscillator

The change of the resonant frequency indicated the beginning moments of emulsification and nucleation of lauric acid near the oscillator surface. The experimental results show that the average crystal size was raised from 139 to 238 nm and the nucleation rate was reduced as the solution concentration increased from 0.05 to 0.25 g/L. When the solution temperature lowers, the crystal grows more rather than new nuclei form in the high concentration solution. The estimated crystal mass from microscopic observation ranges between 18% and 28% of that from the frequency measurement. It was also demonstrated that the proposed monitoring device is useful to investigate the crystallization process in dilute solutions, which often requires large analytical instruments.