The reaction of cerium chloride heptahydrate with salicylic acid and thioproline produced [Ce(Hsal)(2)center dot(tch)]center dot 2H(2)O [Hsal = salicylate (C7H5O3-), tch = thioprolinate (C4H6NO2S-))], which was isolated and characterized by IR, elemental, chemical, and thermogravimetric analysis. The standard molar enthalpies of solution of [CeCl3 center dot 7H(2)O(s)], [2C(7)H(6)O(3)(s)], [C4H7NO2S(s)], and [Ce(Hsal)(2)center dot(tch)center dot 2H(2)O(s)] in a mixed solvent of absolute ethyl alcohol, dimethyl sulfoxide (DMSO), and 3 mol.L-1 HCl were determined by calorimetry to be Delta H-s(m)Theta[CeCl3 center dot 7H(2)O(s), 298.15 K] = -(42.22 +/- 0.37) kJ.mol(-1), Delta H-s(m)Theta[2C(7)H(6)O(3)(s), 298.15 K] = (45.54 +/- 0.37) kJ.mol(-1), Delta H-s(m)Theta[C4H7NSO2(s), 298.15 K] = (21.91 +/- 0.60) kJ.mol(-1), and Delta H-s(m)Theta[Ce(Hsal)(2)center dot(tch)center dot 2H(2)O(s), 298.15 K.] = -(30.87 +/- 0.39) kJ.mor(-1). The enthalpy change of the reaction CeCl3 center dot 7H(2)O(s) + 2C(7)H(6)O(3)(s) + C4H7NO2S(s) = [Ce(Hsal)(2)center dot(tch)]center dot 2H(2)O(s) + 31-1C1(g) + 5H20(1) was determined to be Delta H-r(m)Theta = (263.12 +/- 0.95) kJ center dot mol(-1). From data in the literature, through Hess's law, the standard molar enthalpy of formation of [Ce(Hsal)(2)center dot(tch)]center dot 2H(2)O(s) was estimated to be Delta H-f(m)Theta[Ce(Hsal)(2)center dot(tch)center dot 2H(2)O(s), 298.15 K] = -(2785.7 +/- 3.2) kJ center dot mol(-1).