Some Spectrophotometric Investigations on Iron-Containing Soda–Lime–Silica Glasses. Part II. The Effect of Arsenic and Antimony Oxides.

JSGT 1943 V27 T060-T076

 Glasses, based on that of parent composition 75% SiO₂, 10 CaO and 15 Na₂O, containing varying amounts of iron oxide and of arsenic oxides, were melted at 1400° for 6 hours in platinum in a gas-fired furnace after pre-sintering of the mixture at 750°. The amount of iron oxide added varied from 0·05% to 0·25%, when expressed as Fe₂O₃, and that of arsenic from 0·05% up to about 3% expressed as As₂O₃. Subsequent chemical analysis of the glasses showed the arsenic to be present preponderantly as the pentavalent oxide, As₂O₅. From the spectrophotometric measurements, the effect of arsenic as a decoloriser appeared to be twofold. First, its oxidising effect shifted the ferrous–ferric equilibrium towards the ferric state, and second, its presence caused some of the iron to form a colourless product. For arsenic oxide concentrations greater than 0·5%, the absorption curves indicated that all the iron was present in the ferric form; for concentrations lower than 0·5%, such as is the case in ordinary manufacturing practice, the major decolorising effect was due to the oxidising influence of the arsenic. The results of similar experiments using antimony oxide reproduced closely those due to arsenic oxide.

T. H. Wang & W. E. S. Turner