The statistical graphic analysis of two component glasses in the systems Na2O-SiO2 and K2O-SiO2 has been described in previous articles. The analysis of three component glasses in the system Na2o-CaO-SiO2 by the above method, is described. Several soda-lime silica glasses were melted, care being taken to achieve a high degree of homogeneity. The glasses were stabilised in the transformation region and then cooled at rates of from 1.4 to 22 c per hour. Some were stabilised at temperatures between 500 and 770 C. Density and refractive index measurements at 20C were made on the specimens. The specific refraction was calculated for the glasses, and the contribution of Na2O, CaO and SiO2 determined. The determination of the composition of a soda-lime silica glass could be made by using the specific refraction and the density, or the specific refraction and the refractive index. The sodium oxide content could be calculated with an accuracy of 102% and the lime content could be calculated with an accuracy of 0.4%.
