Abstract
Herein we report the clouding behavior of promethazine hydrochloride (PMT) in the absence and presence of electrolytes and polymers. At constant pH, increasing salt additions caused the cloud point (CP; of PMT containing a fixed concentration of a gemini surfactant) to increase, which is explained on the basis of their position in Hofmeister series and the hydrated radii. With quaternary ammonium salts, CP increased due to adsorption/mixed micelle formation. However, the effect of polymer on CP was found to be dependent upon the number of units present in a particular polymer of poly(vinylpyrrolidone) (PVP) category. Thus, the extent of CP variation by different additives is different (dependent on the nature and structure).