The crystallization behaviour of sulphathiazole.

Previous investigations into the dissolution kinetics of sulphathiazole Form 1 have shown the process to be first order with respect to driving force. However, below 37 degrees first order kinetics did not apply, due to the surface reaction becoming the rate controlling factor. The present study examines the kinetics of crystallization over the temperature range 25 to 50 degrees. Crystallization is a process greatly dependent upon the high-entropy surface integration step which, unlike the dissolution process, is much more sensitive to crystal growth inhibitors. In the absence of inhibitors crystallization above 34 degrees follows first order kinetics but below 34 degrees the process changes to third order. Similar temperature effects on the dissolution of sulphathiazole have been previously reported.