The standard molar reaction enthalpies of two reactions, LaCl3. 7H(2)O(s) + 3CCl(3)COOH(s) (or TCA) = La(TCA)(3). 3H(2)O(s) + 3HCl(g) + 4H(2)O(l) and La(TCA)(3). 3H(2)O(s) + 2C(9)H(7)NO(s) = La(TCA)(C9H6NO)(2)(s) + 2CCl(3)COOH(s) + 3H(2) O(l), were studied by classical solution calorimetry. The molar dissolution enthalpies of the reactants and the products of the two reactions in certain solvent (for one reaction is in 1 mol/l HCl and another in a mixed solution consisting of absolute ethyl alcohol, dimethyl sulfoxide and 4 mol/l HCl) were determined by using an isoperibol calorimeter. From the results and other auxiliary quantities, the Standard molar formation enthalpies of [La(TCA)(3). 3H(2)O, s, 298.15 K] and [La(TCA)(C9H6NO)(2), s, 298.15 K] were determined to be Delta H-f(m)circle dot [La(TCA)3 . 3H2O, s, 298.15 K] = -3063.3 kJ/mol and Delta H-f(m)circle dot [La(TCA)(C9H6NO)(2), s, 298.15 K] = - 1375.6 kJ/mol.