Enthalpies of solution and crystallization of L-ascorbic acid in aqueous solution

Enthalpies of solution for (L-ascorbic acid + water) have been measured in a SETARAM C80 D mixing calorimeter over the composition range of homogeneous solutions at temperatures of 298.15 K and 323.15 K. The results are reported in terms of excess molar enthalpies for {(xC(6)H(8)O(6) + (1 - x)H2O} and molar enthalpies of solution for C6H8O6. The temperature and concentration dependence of the enthalpies of solution are given by a Redlich-Kister equation fitted with the experimental data. Enthalpies of crystallization of L-ascorbic acid in aqueous solutions have been measured at the temperatures (293.15, 298.15, and 303.15) K during unseeded programmed crystallization. The molar enthalpies of crystallization for C6H8O6 obtained experimentally agree well with those calculated from partial molar enthalpies of solution data of C6H8O6. (C) 1998 Academic Press Limited.