The solid-state coordination reaction : 2HSAO(s) + Ni(Ac)(2)(s) --> Ni(SAO)(2)(s) + 2HAc(g) 2HSAO(s) + Co(Ac)(2) . 4H(2)O(s) --> Co(SAO)(2) . 2H(2)O(s) + 2HAc(g) + 2H(2)O(g) have been studied by classical solution calorimetry. The molar dissolution enthalpies of the reactants and the products in a certain solvent (for one reaction is in 6 mol 1(-1) HCl and another in a mixed solution consisting of DMSO and DMF) of this two solid-solid coordination reactions have been measured using an isoperibol calorimeter. From the results and other auxiliary quantities, the standard molar formation enthalpies of [Co(SAO)(2) . 2H(2)O, s, 298.2 K] and [Ni(SAO)(2), s, 298.2 K] at 298.2 K have been determined to be Delta(f)H(m)(theta) [Co(SAO)(2) . 2H(2)O, s, 298.2 K] = -957.205 kJ mol(-1) and Delta(f)H(m)(theta) [Ni(SAO)(2), s, 298.2 K] = -403.336 kJ mol(-1).