Solubility and dissolution enthalpy of xanthine

At a constant ionic strength corresponding to human urine (I-c=0.300 mol.dm (-3)), the solubilities of xanthine were measured as a function of -Ig{c(H)/c(0)} (c(0)=1 mol.dm(-3)) at the temperatures T = 298.15 K and T = 310.15 K, respectively. Highly reproducible solubility and dissociation constants were obtained. Also, for the first time, the dissolution enthalpy of xanth ine was determined calorimetrically. The values of this quantity obtained f rom both calorimetric determination and temperature dependence of solubilit y equilibrium constants are thermodynamically consistent. (C) 2001 Academic Press.