The standard molar reaction enthalpies of two reactions, CeCl3.7H(2)O(s) + 3CCl(3)COOH(s)(or TCA) = Ce(TCA)(3).3H(2)O(s) + 3HCl(g) + 4H(2)O(l) and Ce(TCA)(3).3H(2)O(s) + 2C(9)H(7)NO(s) = Ce(TCA)(C9H6NO)(2)(s) + 2CCl(3)COOH(s) + 3H(2)O(l), were studied by classical solution calorimetry at 298.15 K. The molar dissolution enthalpies of the reactants and the products in certain solvent (the first reaction in 1 mol/l HCl, the second in a mixed solution consisting of absolute ethyl alcohol, dimethyl sulfoxide and 4 mol/l HCl) have been measured by using an isoperibolic calorimeter at 298.15 K. From the results and other auxiliary quantities, the standard molar formation enthalpies of [Ce(TCA)(3).3H(2)O, s, 298.15 K] and [Ce(TCA)(C9H6NO)(2), s, 298.15 K] were determined to be Delta(f) H-m(theta) [Ce(TCA)(3).3H(2)O, s, 298.15 K] = -3059.9 kJ/mol and Delta(f) H-m(theta) [Ce(TCA)(C9H6NO)(2), s, 298.15 K] = -1368.9 kJ/mol. (C) 2003 Elsevier Science B.V. All rights reserved.