We have developed correlations for the Henry's constant k H and the vapor-liquid distribution constant K D for 14 solutes in H 2 O and seven solutes in D 2 O. The solutes considered are common gases that might be encountered in geochemistry or the power industry. Solubility data from the literature were critically assessed and reduced to the appropriate thermodynamic quantities, making use of corrections for nonideality in the vapor and liquid phases as best they could be computed. While the correlations presented here cover the entire range of temperatures from near the freezing point of the solvent to high temperatures approaching its critical point, the main emphasis is on representation of the high-temperature behavior, making use of asymptotic relationships that constrain the temperature dependence of k H and K D near the critical point of the solvent.

A Raman spectroscopic study of aqueous solutions of MgSO, as function of concentration and temperature was performed. From the analysis of the band profile of the internal vibrations of the sulphate ion, the spectroscopic ionic association constant was calculated at different temperatures. It was found that the association is solvent separated in the ranges of concentration and temperature studied. The large differences observed between the values obtained for the spectroscopic association constant and those obtained from macroscopic measurements were interpreted on the basis of a four-step solvent-separated dehydration mechanism. It is, assumed that the Raman spectra reflect only the shortdistance force acting on the sulphate anions. The contribution of the long-range forces for the consecutive steps were calculated using the Bjerrum equation. Good agreement between the overall association constant thus calculated and the macroscopic value was found in the concentration and temperature ranges studied.

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The solubilities of H 2 and of N 2 in water have been determined over a wide temperature range. The thermodynamic analysis of the data allowed the calculation of Henry's constants (kH") as function of temperature from room temperature to 636 K; other thermodynamic quantities of dissolution have been derived from the temperature dependence of kH". With a semiempirical perturbation method it is possible to describe the experimental behaviour and to predict the partial molar volume and heat capacity of the solutes over all the temperature range. This calculation procedure requires the knowledge of the hard-sphere radii of the solute gases and their (linear) temperature dependence which may be determined from solubility data covering only a reduced temperature range extending to about 400 K. P ftL = Yt R (l -x)pT(I)cI>t*(pT, T) exp J(Vt*IRT)dp (lc) PT ftL = ftG (1a) ft G = (l -y)p cI>t (p, T,y ) Data TreatmentThe thermodynamic conditions of equilibrium for liquidvapour equilibrium in binary system are [1,5]:Component 1, solvent:dients in the equilibration cell. Accordingly the temperature of the binary mixture was measured continuously during the equilibration period with two thermocouples, one located in the lower part of the cell and always immersed in the dense phase, another in the upper part of the cell where the vapour phase was present (the actual difference between the temperatures recorded by the thermocouples never exceeded 0.2 K). The thermocouples were calibrated in a molten salt bath against a standard platinum resistence with a precision of 0.1 K at 373 K which rose to 0.3 K as the temperature approached 673 K. In order to minimize heat losses in the cell, all the valves were separated from the cell body by small diameter tubing. Pressures were measured with Bourdon gauges calibrated with a precision of 0.2% of the full scale value. Adequate amounts of water and gas were introduced into the cell and the temperature set at the chosen value. When equilibrium between the vapour and the liquid phases was established a small sample of the liquid phase was withdrawn from the cell through a capillary and introduced into a previously evacuated glass cell; the mass of the sample was determined by weighing. The glass cell was then connected to a gas burette and immersed in a cooling bath so that only the solute gases contributed significantly to the total pressure in the gas burette. Liquid nitrogen at the normal boiling point (77.4 K) or chloroform at its normal melting point (209.6 K) were employed in the cooling baths. The manometric fluid was mercury or silicone (Dow 200/50, having a density of 0.9555 g' em -3 at 293 K). The temperature of the cooling bath and the manometric fluid were chosen so that the amount of solute gas could be determined through the measurement of the pressure in the gas burette with a precision better than 0.2% in all cases. When chloroform was used, the value of the vapour pressure of ice at the melting point of CCIJH was discounted from the reading obtained for the total pressure. (...