The influence of Na2, CO3, K2CO3, and Li2CO3addition on the relative volatility factor α of light and heavy water ai temperatures close to the isotope effect inversion temperature has been investigated. The measurements for Na2CO3and K2CO3solutions have been made in the temperature range. 100–330 °C at various salt concentrations. In the case of Li2CO3temperature range and concentration was limited by the solubility of this salt. The factor α was determined by analysis of gas and liquid phases at equilibrium. Data on pure waters obtained by other investigators are listed for comparison. The temperature dependence of factor α for salt solutions and pure waters is presented in the form of equations derived from experimental data.