The activity of sodium oxide in molten float glass by EMF measurements

The Na₂O activity in the molten float glass composed of 13.2 m/o Na₂O, 70.2 m/o SiO₂, 10.0 m/o CaO, 5.9 m/o MgO, etc. was determined in the temperature range from 1260 to 1380 K by means of galvanic cells using Na-β″-alumina as solid electrolyte. The Na₂O activity, a_Na2O, accompanying the reaction Na₂O (dissolved in Na₂O-WO₃ melt)=Na₂O (dissolved in molten glass) was found to be given by as a function of temperature, and the relative partial molar enthalpy of Na₂O was calculated to be .