Abstract
The properties of water of crystallization of sodium prasterone sulfate (DHA·SO3Na·2H2O) were investigated by thermometric measurements. The anhydrous form (DHA·SO3Na) was very hygroscopic, and easily transformed to the dihydrate. The dihydrate was in a stable phase under ordinary storage conditions. If the released water molecules were not effectively exhausted in the dehydration process, a liquefaction phenomenon due to the interaction between water molecules and DHA·SO3Na was observed. The activation energy (ΔE) of the dehydration reaction from the dihydrate to the anhydrous form was determined by an isothermal method and a non-isothermal method (Ozawa method) under a constant water vapor pressure, PH2O=14.9 mmHg. ΔE obtained by the isothermal method was 31.5 kcal/mol and ΔE obtained by the Ozawa method was 31.3 kcal/mol.
