PRESSURE-DEPENDENCE OF THE SOLUBILITY OF NITROGEN, ARGON, KRYPTON, AND XENON IN WATER

Measurements are reported for the pressure dependence of the Ostwald L and mole-fraction X2 solubilities for nitrogen, argon, krypton, and xenon in water at 25.0°C. The approximate pressure ranges were: N2, 44-116 atm; Ar, 22-101 atm; Kr, 33-81 atm; and Xe, 5-48 atm. Our experimental technique is a modified Van Slyke method which allows the simultaneous determination of L, x2, and partial molar volume ν2 of the solute gas in the solvent. For N2, Ar, and Kr we observe deviations from Henry's Law, f2 = kHx2 which vary linearly with pressure. For example, the measured values of Henry's constant range from kH (25°C, 44.6 atm) = 90 269 atm to k H (25°C, 115.8 atm) = 100 340 atm for N2 in water. Extrapolation of the data to low pressure yields results for L and x2 which agree with literature values. For Xe we observe a sharp increase in Henry's constant at pressures above 20 atm. The measured partial molar volume also changes sharply from 47 to ∼ 125 cm3/mol. This is attributed to the observed onset of ice-like clathrates at pressures above 20 atm. The solubility data are analyzed in terms of the Kirkwood-Buff solution theory, and the role of hydrophobic interactions is discussed. For the Kr-water system, we compare the experimental results to recent computer simulations. We also use statistical mechanics arguments to introduce a new solubility parameter which is useful in understanding high-pressure measurements. We conclude by discussing extensions of this work to other gas-liquid systems. © 1990 American Institute of Physics.