Vapour pressures of water over saturated solutions of cesium chloride, cesium bromide, cesium nitrate, cesium sulfate, cesium formate, and cesium oxalate were determined as a function of temperature. These vapour pressures were used to evaluate the water activities, osmotic coefficients and molar enthalpies of vapourization. Molar enthalpies of solution of cesium chloride, Delta H-sol(m)(T = 295.73 K; m = 0.0622 mol . kg(-1)) = (17.83 +/- 0.50) kJ . mol(-1); cesium bromide, Delta H-sol(m)(T = 293.99 K; m = 0.0238 mol . kg(-1)) = (26.91 +/- 0.59) kJ . mol(-1); cesium nitrate, Delta H-sol(m)(T = 294.68 K; m = 0.0258 mol(-1) . kg(-1)) = (37.1 +/- 2.3) kJ . mol(-1); cesium sulfate, Delta H-sol(m)(T = 296.43 K; m = 0.0284 mol . kg(-1)) = (16.94 +/- 0.43) kJ . mol(-1); cesium formate, Delta H-sol(m)(T = 295.64 K; m = 0.0283 mol . kg(-1)) = (11.10 +/- 0.26) kJ . mol(-1) and Delta H-sol(m) (T = 292.64 K,m = 0.0577 mol . kg(-1)) = (11.56 +/- 0.56) kJ . mol(-1); and cesium oxalate, Delta H-sol(m)(T = 291.34 K; m = 0.0143 mol . kg(-1)) = (22.07 +/- 0.16) kJ . mol(-1) were determined calorimetrically. The purity of the chemicals was generally greater than 0.99 mass fraction, except for HCOOCs and (COOCs)(2) where purities were approximately 0.95 and 0.97 mass fraction, respectively. The uncertainties are one standard deviations. (C) 2005 Elsevier Ltd. All rights reserved.