Effect of Silica & Sodium Oxide

JSGT 1921 V05 T121-T123

SILICA after fusion is noteworthy by reason of its very low thermal coefficient of expansion, which makes it extremely valuable for conversion into articles which have to res st sudden changes of temperature. This property of low thermal expansion it also bestows on sllicate gla.sses, although whether to the same extent
as in the free state is not yet clear. In previous attempts to calculate the thermal coefficient of expansion of glasses, * we have assumed that silica takes \vith it into the glasses this same low expansion rate. This certainly is an assumption , although the agreement between the calculated and the experimental results
does at any rate not contradict it.

S English and W E S Turner