Solubility of oxygen and inert substances in water

The solubility of oxygen in water at different temperatures has been analys ed in the light of a statistical thermodynamic model. According to the mode l, the oxygen-water system is considered as a convoluted ensemble consistin g of a reacting system, formed by oxygen molecules and structured solvent w ith enthalpy difference DeltaH(phi) between discrete enthalpy levels, and o f a non-reacting system with continuous distribution of enthalpy levels. Th e enthalpy change of the reaction between oxygen and water, as determined e ither by measuring the solubility of substances in water at different tempe ratures either by measuring heat calorimetrically, is partially absorbed by some n(w) water molecules. The relaxed water molecules occupy part of the cavity formed around solute. The part of heat absorbed, DeltaH(w) depends l inearly upon the temperature and causes the observed changes with temperatu re of apparent enthalpy DeltaH(app) for the dissolution of oxygen and many other inert substances in water. The number n(w) is proportional to the siz e of solute as shown by comparison with noble gases and other inert substan ces slightly soluble in water. The solubilization process of all these subs tances is clearly analogous. (C) 2000 Elsevier Science Ltd. All rights rese rved.