The Effect of Gases on a Commercial Glass Containing Lead Oxide

JSGT 1932 V16 T121-T130

The investigation was undertaken to examine the nature and causes of the “scum” which had been observed on the surface of molten lead oxide–silica glass in an oil-fired tank furnace. It is shown that the “scum” consisted of a precipitation of silica mainly in the form of alpha-cristobalite, and that this scum was not produced by heat alone. Of the gases used in the investigation and likely to be in the furnace atmosphere sulphur dioxide is the only one which had any effect on the molten glass heated to 1200°. Its effect, per se, was to produce a precipitation of silica identical in crystalline form with that found in practice, but, admixed with oxygen, gave rise to a complicated deposit of sulphates of sodium, potassium and lead in addition to the silica. Of the modified glasses made to try to prevent the formation of this “scum,” that containing a small proportion of boric oxide was found to be the most stable.

J. H. Partridge