Vapour pressures of saturated aqueous solutions of tartaric acid, sodium hydrogen tartrate, sodium tartrate, potassium tartrate, calcium tartrate, barium tartrate, citric acid, disodium hydrogen citrate, sodium citrate, and potassium citrate were determined in the temperature range (277 to 317) K using an electronic hygrometer. Only for tartaric acid, sodium tartrate, potassium tartrate and citric acid was it possible to compare the determined vapour pressures with the isoteniscopic results available in the literature. The measured vapour pressures allow the determination of water activities and molar enthalpies of vaporization of solutions at saturation conditions and osmotic coefficients if the solubilities of these compounds in water are known.