Thermodynamic properties of polymorphic forms of theophylline. Part II: The enthalpies of solution in water at 298.15 K

Abstract

The enthalpies of solution \( \Updelta_{sol}^{{}} H_{m}^{{}} \) of polymorphic forms I and II of theophylline in water at 298.15 K using the isoperibol solution calorimeter have been determined in the range of concentration (0.311–1.547) · 10−3/mol · kg−1. The enthalpies of hydration \( \Updelta_{hyd}^{{}} H_{m}^{o} \) were determined from the experimentally obtained the enthalpies of solution for aqueous solutions and previously determined enthalpies of sublimation \( \Updelta_{s}^{g} H_{m}^{o} . \)