Liquid inclusions in crystals produced in suspension crystallization

Abstract

Sodium chloride, potassium chloride, succinic acid and potassium hydrogen phthalate crystals were crystallized batchwise in an agitation vessel and the total volume of liquid inclusions per crystal, V (μm 3), was measured as a function of crystal size, d (μm). The found data of the total volume, including literature data from a continuous crystallizer, was correlated with a simple equation, V=4.0×10 −6 d 4. Most of the inclusions observed in sodium chloride and potassium chloride crystals were layer inclusions, which were aligned two-dimensionally in parallel with crystal faces. This type of inclusion pattern was suggested, with the help of the results of additional in situ experiments under a microscope, to be caused by the adhesions of small crystals to growing crystals and mechanical contacts imposed to these crystals during growth. Although the layer pattern was not found in the other crystals examined, the same mechanism was considered to work for the inclusion formation.