Density and structures of ternary silicate melts

Abstract

Using the maximum bubble pressure method the (density, composition) relationships occurring as the result of replacement of Fe²⁺ ions in an iron silicate by Ca²⁺, Mn²⁺, Co²⁺ and Ni²⁺ ions along the composition line containing 29 mole % silica in the respective ternary silicate systems have been determined at 1410°C. The calculated (oxygen density, composition) relationships indicate that a change in the anionic configuration of ternary silicate melts occurs along iso-silica mole fraction lines in the system and this conclusion agrees with polymerization models of basic silicates. Correlation is obtained between the composition dependence of the activities of constituent metal oxides in ternary silicate melts and the composition dependence of the anionic configuration. The anionic configuration, or degree of polymerization of silicate anions occurring in a basic silicate melt, is discussed in terms of the relative energetics of possible ionic associations.