PbO-SiO₂ 2 元系およびそれを含む3元系融体におけるPbOの活量

抄録

The Knudsen cell-mass spectrometer combination is used to study the thermodynamic properties of liquid PbO-SiO₂, PbO-CaO-SiO₂, PbO-MgO-SiO₂, PbO-BaO-SiO₂, PbO-NiO-SiO₂, and PbO-CoO-SiO₂ systems. First, the activities of PbO in binary melts are determined in the temperature range from 800 to 1020°C by application of the monomer-dimer technique. The results obtained are in good agreement with the previous results obtained by other methods. Second, the ratios of the activities of PbO in the ternary silicate melts containing 50 mol% SiO₂ to that in the corresponding binary silicate melt are determined by the same technique in the temperature range from 1050 to 1250°C.
The obtained results are discussed on the basis of the thermodynamic model of silicate melts derived by the application of a quasi-chemical treatment to the random network model of silicates. The results obtained indicate that the standard free energy change of reaction (1) of a ternary melt is not
(This article is not displayable. Please see full text pdf.)
\ oindentgiven by the arithmatic mean of those of the parent binary melts. The activity ratios obtained from PbO-BaO-SiO₂ and PbO-NiO-SiO₂ melts are compared with viscosities and activation energies of viscous flow of these melts on the basis of the model mentioned above. The behavior of these properties of these melts below X_BaO or X_NiO=0.10 indicates that the silicate ions in these melts are more highly depolymerized than in the corresponding binary PbO-SiO₂ melts, and consequently NiO in the ternary melt is apparently more basic than PbO in the melt in contrast with NiO which is more acidic than PbO in binary silicate melts. The apparent changes of basicities of basic oxides in the other ternary melts are also discussed.