DENSITY OF SOME TITANIUM-BEARING SILICATE LIQUIDS AND THE COMPOSITIONAL DEPENDENCE OF THE PARTIAL MOLAR VOLUME OF TIO2

The densities of thirteen silicate liquids along the Na2SiO3-TiO2 and CaSiO3-TiO2 joins and six other titanium-bearing silicate liquids of the general formula X2/nn+TiSiO5 (where X = Li, Na, K, Rb, Cs, Ca, Sr, Ba) have been measured in equilibrium with air using the double Pt bob Archimedean method. The Na2SiO3-TiO2 join was investigated from 10-50 mole% TiO2 in the temperature range 1000-1150-degrees-C whereas the CaSiO3-TiO2 join was investigated from 10-80 mole% TiO2 in the temperature range of 1400-1625-degrees-C. Density increases with TiO2 content along both joins. Partial molar volumes of the binary endmembers, Na2SiO3 and CaSiO3, and of TiO2 have been computed. The partial molar volume of Na2SiO3 agrees well with that determined by BOCKRIS et al. ( 1955). The partial molar volume of CaSiO3 is in disagreement with that of TOMLINSON et al. (1958). The partial molar volume of TiO2 derived from a linear fit to the Na2SiO3-TiO2 join is 27.6(3) cm3/mole at 1150-degrees-C. The partial molar volume of TiO2 derived from linear extrapolation of the CaSiO3-TiO2 data to TiO2 at 1600-degrees-C is 24.3 (4) cm3/mole. Comparison of the partial molar volume data from these binary joins with TiO2 liquid density data (DINGWELL, 1991 ) requires the existence of a large positive excess volume in the Na2SiO3-TiO2 system at 1150-degrees-C.