The Effect of Small Additions of Sodium Sulphate on the Reactions in the Mixture 6SiO₂+Na₂CO₃+CaCO₃

_{JSGT 1937 V21 T359-T367}

 _{The addition of amounts up to 5% of sodium sulphate to a mixture of molecular composition 6SiO2.Na2CO3.CaCO3 has no noteworthy effect on the rate of decomposition at 700° or on the amount of soluble silica formed at 700° or 800°. At temperatures of 1200–1400° the mixture without sodium sulphate begins to melt sooner than that containing from 1 to 3% sodium sulphate added in molecular replacement of carbonate, but with 5% of sodium sulphate the rate of melting at 1400° is practically the same or even slightly quicker than that of the sodium carbonate mixture only. At all temperatures from 1200–1400° the elimination of small seed is improved by addition of from 1 to 5% of sulphate. At 1400° much of the decomposition of sulphate in the mixture takes place in the early stage of the melting process and thereafter loss of residual SO3 is slow.}

J. E. Stanworth & W. E. S. Turner