A Study of the Possibility of Reducing the Iron Oxide Content of Molten Soda-Lime-Silica Glasses by the Action of Chlorides

JSGT_1939_V23_T253_T264

Meltings have been made, mainly at 1400°, in platinum, of a glass of basic composition SiO₂ 75.0, CaO 9.2, Na₂O 15.8%, to which either 0.1 or 0.2% of iron oxide as Fe₂O₃ in the glass was added and the batch melted with the addition of one of the chlorides, ferric chloride, sodium, potassium or ammonium chloride, in amount equivalent, in terms of Cl, to 0.1, 0.2 or 0.4% of the glass. Analysis of the resultant glasses showed that during the melting process iron as well as chlorine were lost by volatilisation, probably as ferric chloride, the losses being very variable, but being, in general, lowest with sodium chloride and greatest with ammonium chloride. In no case did the loss of iron oxide reach 25% of the original amount, and, with sodium chloride, in no case did it reach 10%. Although ammonium chloride was the most effective of the reagents in eliminating iron oxide, its use in practice would be of doubtful benefit owing to its tendency to produce colouring effects varying from yellow to brown.

H. Marshall Bateson, B.Sc.Tech., and Professor W. E. S. Turner