The molar enthalpies of solution of sodium oxalate Delta(so1)H(m)(Na2C2O4; T = 296.57 K, m = 0.00768 mol (.) kg(-1)) =(16.59 +/- 1.32) kJ (.) mol(-1) and potassium oxalate monohydrate Delta(so1)H(m)(K2C2O4 (.) H2O; T = 299.01 K, m = 0.0274 mol (.) kg(-1)) = (29.31 +/- 0.98) kJ (.) mol(-1) were calorimetrically determined. The case of ammonium oxalate monohydrate, Delta(so1)H(m)((NH4)(2)C2O4 (.) H2O; T = 296.99 K; m = 0.03401 mol (.) kg(-1)) = (35.0 +/- 4.9) kJ (.) mol(-1) was previously considered in [11]. Solubilities of ammonium oxalate, sodium oxalate and potassium oxalate in water were measured in the (273 to 333) K temperature range. Presented data are compared with the literature results. (C) 2004 Elsevier Ltd. All rights reserved.