Post‐crystallization cooling behavior of aqueous supersaturated ammonium dihydrogen phosphate solutions containing acetone and methanol antisolvents added at different rates

Abstract

Experimental results of post‐crystallization cooling behavior of aqueous supersaturated ammonium dihydrogen phosphate (ADP) solutions containing acetone and methanol antisolvents fed at different rate RA are described and discussed. The supersaturated solutions were contained in a double‐walled crystallizer connected to a thermostating arrangement maintaining the temperature at 30 °C. It was found that: (1) there is a steady decrease in temperature Ts of aqueous ADP solutions with increasing time t, which follows Newton's law of cooling, with constant K as characteristic of solution composition and its value for a system increases with an increase in RA, and (2) at a particular acetone and methanol feeding rate RA, the value of constant K for aqueous ADP solutions is much higher than that obtained from the data of decrease in the temperature Tm of pure water. The experimental results are discussed from consideration of a steady decrease in solution supersaturation with increasing t as a result of diffusion of ions/molecules involved in transporting heat from aqueous ADP solutions contained in the crystallizer to the thermostating system.