Freezing temperature lowerings of aqueous solutions of tartaric acid, sodium hydrogen tartrate, sodium dihydrogen citrate, potassium dihydrogen citrate, disodium hydrogen citrate, sodium citrate and potassium citrate were determined. These values and those taken from the literature for potassium tartrate were used in the determination of the osmotic and activity coefficients in the studied systems, via the numerical integration of the Gibbs-Duhem equation. (C) 2003 Elsevier Science Ltd. All rights reserved.