ABSTRACTNineteen soda‐lime glasses covering the commercial field were prepared, melted, and fined for 2 hours. The chemical composition of the raw materials was determined by usual analytical methods; the refractive index was determined by an Abbé refractometer; density, by the normal suspension method; and softening point, by the Littleton method with the furnace as specified inJour. Amer. Ceram. Soc.,10[4], 259‐63 (1927).The data indicate the following points: (1) When the silica was kept constant by increasing the dolomitic lime at the expense of soda an increase in softening point of 11 to 12°C per 1% increase was obtained. Likewise the density increases 0.004 and the refractive index 0.0015 per 1% increase of lime. (2) When the soda was kept constant the softening point was practically constant. The density decreases 0.011 and the refractive index 0.0030 per 1% increase of silica at the expense of lime. (3) When the lime was kept constant the increase in softening point per 1% increase in silica varied as follows : 5% lime 21°C, 8% lime 17°C, 10% lime 15°C, and 12% lime 12°C. The density decreased 0.008 and the refractive index 0.0015 per 1% increase in silica at the expense of soda. (4) A thermo‐chemical relation of the softening points and the chemical compositions (calculated) closely paralleling the “liquidus” surfaces of Feild and Roysters' system