RAPID METHOD FOR DETERMINING CRITICAL VAPOR PRESSURE

摘要

A method of determining the critical vapor pressure of a hygroscopic material, such as a drug. A drug sample is placed in a substantially isothermal environment. A vapor, such as water vapor, at a given pressure is then placed in the ambient air over the drug. The rate of heat production from this sample at the given water vapor pressure, or the humidity of the air above the sample, is then measured. The water vapor pressure over the drug is gradually increased. Simultaneously, the rate of increase in heat production from the drug sample, or the rate of change of the relative humidity of the air above the drug sample, is measured. A marked increase in the rate of heat production generated by the drug, or a marked change in the relative humidity of the air over the sample, signals the attainment of the critical water vapor pressure.