Density of some ti~um-Bering silicate liquids and the ~omposition~ depeudence of the partial molar volume of Ti02

The densities of thirteen silicate liquids along the NaZSiOs-TiOz and CaSiOs-TiOZ joins and six other titanium-bung silicate liquids of the general formula X ;$,TiSiO, (where X = Li, Na, K, Rb, Cs, Ca, Sr, Ba) have been measured in equilibrium with air using the double Pt bob Archimedean method. The NazSiOj-TiOz join was investigated from lo-50 mole% Ti02 in the temperature range lOOOI 150°C whereas the CaSi03-TiOz join was investigated from lo-80 mole% Ti02 in the temperature range of 14OO-1625’C. Density increases with TiOz content along both joins. Partial molar volumes of the binary endmembers, Na2Si03 and CaSi4, and of Ti02 have been computed. The partial molar volume of Na2Si03 agrees well with that determined by BOCKRIS et al. ( 1955). The partial molar volume of Casio, is in disagreement with that OfTOMLINSON et al. ( 1958). The partial molar volume of Ti02 derived from a linear fit to the Na2Si03-Ti02 join is 27.6( 3) cm3/mole at 1150°C. The partial molar volume of TiO* derived from linear extrapolation of the CaSiOs-TiOz data to TiOz at 1600°C is 24.3(4) cm3/mole. Comparison of the partial molar volume data from these binary joins with Ti02 liquid density data ( DINGWELL, 199 1) requires the existence of a large positive excess vdume in the Na$iOj-TiOz system at 1150°C.