ENTHALPIES OF SOLUTION AND CRYSTALLIZATION OF L-ASCORBIC-ACID IN AQUEOUS-SOLUTION

Enthalpies of solution for (L-ascorbic acid + water) have been measure d 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 re sults 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 te mperature and concentration dependence of the enthalpies of solution a re given by a Redlich-Kister equation fitted with the experimental dat a. Enthalpies of crystallization of L-ascorbic acid in aqueous solutio ns 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 th ose calculated from partial molar enthalpies of solution data of C6H8O 6. (C) 1998 Academic Press Limited.