Crystal formation of BaCl2 and NH4Cl using a supercritical fluid antisolvent

The supercritical antisolvent (SAS) process has been used to produce crysta ls of barium chloride (BaCl2) and ammonium chloride (NH4Cl) from solutions of dimethyl sulfoxide (DMSO). Crystallization was performed by introducing carbon dioxide into the DMSO solutions at different injection rates. Variat ions in crystal properties such as particle size, crystal habit, and intern al space lattice were observed in the SAS processed crystals. The average p article size of the crystals decreased with increasing carbon dioxide injec tion rate for both compounds. As the injection rate increased, the crystal habit of BaCl2 was modified from an equant to an acicular habit, and that o f NH,CI changed from an equant to a tabular habit. X-ray diffraction patter ns showed the transition of the space lattice of BaCl2 from the orthorhombi c to hexagonal crystal system. The use of the SAS process for the separatio n of BaCl2 and NH4Cl mixtures in DMSO was also investigated. (C) 2000 Elsev ier Science B.V. All rights reserved.