Controlling crystallisation with audible low frequency sound

Abstract

We show that low-frequency audible sound is able to drive the crystallisation of distinct solid forms of organic compounds in solution crystallisation. Using a home-made apparatus, suspended or mechanically coupled crystallisations were performed. Crystallisations with the compounds, ROY in ethanol and isopropanol and anthranilic acid in water, solidified out single polymorphs, concomitant forms, and preferred orientation depending on the sound parameters of frequency (Hz) and amplitude (dB), evidencing a sound controlled- crystallisation. Unexpected outcomes include the fiber-like morphology of the ROY Y form due to pronounced (010) preferred orientation, and the anthranilic acid form I obtained from unlikely aqueous solvent.