The chemical compositions of soda-lime glasses were expressed in molecular contents and in relation to 1.0 mole of silica. A balanced orthogonal latin square system was constructed with five variables at five levels each. A statistical analysis showed that if compositions are calculated on a molecular basis, the viscosity of glasses can be calculated from the composition with good accuracy. The effects of glass constituents on viscosity are linear with the molecular contents and additives. No interaction between the glass constituents could be established. So-called anomalies exist only if the glass composition is calculated in weight percentages. Three equations have been established for calculating the constants in the Fulcher equation from glass compositions.
