224. The quantum mechanical correction for the high temperature van der waals interaction of light gases and surfaces. A new method of determining surface area: M.P. Freeman, J. Phys. Chem., 64, 32–37, Jan. 1960

Abstract

Solid + liquid phase diagrams have been obtained from cooling and warming curves for binary mixtures formed from POCl3 + SnCl4, + GeCl4, + SiCl4, and + CCl4. A congruently melting compound of empirical formula SnCl4 · 2POCl3 forms. The other mixtures show no compound formation. Solid solutions form over a considerable part of the composition range for POCl3 + CCl4. Exploratory measurements show no compound formation between SnBr4 and POCl3 or Sn(CH3)4 and POCl3. A comparison is made between the experimental freezing curves for SiCl4 and GeCl4 in POCl3 with the curves calculated assuming ideal-mixture behavior. Both mixtures show positive deviations from Raoult's law. The deviations are larger for SiCl4 + POCl3 suggesting less attraction between unlike molecules than in GeCl4 + POCl3. The lack of compound formation of phosphorus oxychloride with all the tetrachlorides except that of tin and the deviations from ideal-mixture behavior are explained in terms of steric effects and the electron-accepting ability of the Group IVA elements.