Vapour pressures of water over saturated solutions of ammonium bromide, ammonium dihydrogen phosphate, ammonium thiosulfate, ammonium persulfate, ammonium acetate, ammonium oxalate and ammonium tartrate were determined as a function of temperature. These vapour pressures were used to evaluate the water activities, osmotic coefficients and molar enthalpies of vaporization. Molar enthalpies of solution of ammonium bromide Delta(sol)H(m)(NH4Br, T = 293.97 K, m = 0.1030mol . kg(-1)) = (17.4 +/- 0.5) kJ . mol(-1); ammonium hydrogen carbonate Delta(sol)H(m) (NH4HCO3, T = 293.06 K, m = 0.06372mol . kg(-1)) = (26.4 +/- 1.1) kJ . mol(-1); ammonium dihydrogen phosphate Delta(sol)H(m)(NH4H2PO4, T = 297.08 K, m = 0.08774mol . kg(-1)) = (15.0 +/- 1.1) kJ . mol(-1); ammonium phosphate trihydrate Delta(sol)H(m)(NH4)(3)PO4.3H(2)O, T = 296.29 K, m = 0.04960 mol . kg(-1)) = (24.1 +/- 1.4)kJ . mol(-1); ammonium thiosulfate Delta(sol)H(m)((NH4)S2O3,T = 293.86 K, m = 0.03410 mol . kg(-1)) = (15.8 +/- 0.7) kJ . mol(-1); ammonium oxalate monchydrate Delta(sol)H(m)((NH4)(2)C2O4.H2O, T = 296.99 K, m = 0.03401 mol . kg(-1)) = (35.0 +/- 4.9) kJ . mol(-1) and ammonium tartrate Delta(sol)H(m)((NH4)(2)C4H4O6, T = 297.14 K, m = 0.02745 mol . kg(-1)) = (28.4 +/- 0.6) kJ . mol(-1) were determined calorimetrically. (C) 2003 Elsevier Science Ltd. All rights reserved.