Further Studies on the Influence of Sodium Chloride on the Iron Oxide Content of Molten Soda-Lime-Silica Glasses

JSGT 1940 V24 T041-T045

Glasses of the basic percentage composition SiO₂ 73.5, Na₂O 16.5, CaO 10.0 and containing 0.08% Fe₂O₃ were melted in platinum at 1500° in a gas-fired furnace both without and with the addition of sodium chloride and certain other volatile materials. The amount of sodium chloride added in all cases was equivalent to 0.2% Cl in the glass. The other volatile materials added with the sodium chloride and their amounts in different series were: (a) selenium, 0.4 oz. per 1000 lb. of sand, with cobalt oxide, in amount appropriate to decolourise the iron oxide, (b) borax, to yield 2.0% in the glass, (c) ammonium sulphate, 7.5 parts per 1000 of sand. Analysis of the resulting glasses showed that the losses of iron oxide in the presence of sodium chloride and other volatile constituents were: (a) sodium chloride alone, 11.3%, (b) with selenium 15.0%, (c) with boric oxide 17.5%, (d) with ammonium sulphate 28.8%.

R. Halle, B.Sc.Tech., and Professor W. E. S. Turner