Surface Tension, Density, Viscosity, and Electrical Resistivity of Molten Binary Alkaline‐Earth Borates

Results of an investigation of some properties of the systems CaO‐B 2 O 3 , SrO‐B 2 O 3 , and BaO‐B 2 O 3 are reported. The formation of two liquids at low RO concentrations limited the range of compositions which could be measured. The values of surface tension and temperature coefficient of surface tension obtained for compositions where two immiscible liquids exist corresponded closely to those for pure B 2 O 3 . At RO concentrations above the two–liquid regions the surface tension rose sharply with increasing RO content. The densities in the liquid range as well as at room temperature were in the order Ba > Sr > Ca. The introduction of RO into B 2 0 3 caused contractions in the glass network; the order of the contracting effect was Ca > Sr > Ba. Neither the method of Huggins or of Stevels was satisfactory for representing the density behavior of these glasses. The viscosity isotherms of barium borate liquids in the temperature range 850° to 950°C. showed maxima at about 22 to 23 mole yo BaO; the other two systems were too fluid for the counterbalanced sphere apparatus used in this work. The equivalent conductance increased with RO concentration; the order for both specific and equivalent conductance at corresponding concentrations was Ba > Sr > Ca.