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Solubility of Gases in Glass. II. He, Ne, and H2 in Fused Silica

1972; American Institute of Physics; Volume: 43; Issue: 4 Linguagem: Inglês

10.1063/1.1661371

1520-8850

James F. Shackelford, Perry L. Studt, Richard M. Fulrath,

Phase Equilibria and Thermodynamics

The statistical thermodynamics of the gas-in-glass system provides a basic model of both physical and chemical solubility. The physical solubility result is essentially equivalent to that for monatomic solubility. The chemical solubility result is dependent upon the specific system involved. The model was compared with experiment for a variety of systems. Helium and neon in fused silica were examples of the physical solubility of monatomic gases. Variations of the thermal history of the fused silica did not appear to have a measurable effect on physical solubility as evidenced in the helium data. Hydrogen in fused silica was an example of the physical solubility of polyatomic gases. Physical solubility was measured by a modified Seiverts technique and was characterized by a linear dependence on pressure. Binding energies for the physically dissolved species were of the order expected for van der Waals bonding. Vibrational frequencies were on the order of 1013 sec−1 with the heavier species having the lower frequencies. Hydrogen in fused silica was also an example of the chemical solubility of polyatomic gases. The literature gave data for the chemical solution of hydrogen in fused silica, but the fused silica of this study did not, perhaps because of the presence of water-produced hydroxyls. Comparison of the model with the literature data showed a p1/2 pressure dependence for the solubility (indicative of dissociation) and a binding energy of about 63 kcal/mole (indicative of chemical bonding).