The vapour pressure over water (1) sodium chloride (2) and sorbitol (3) ternary solutions of different concentrations (m(i) <= 4, i: 2,3) was measured at 338 K and 348 K. Starting from these data, the values of the experimental water activity (a(1)) were calculated. These data and those obtained for other authors at 293 K, 298 K and 308 K were correlated with a previously developed equation for a(1)(m(2), m(3)). Thus, the equation parameters and their corresponding temperature dependences were obtained. The corresponding root mean square deviation was evaluated, being in all cases less than 0.005. (C) 2016 Elsevier B.V. All rights reserved.