Jacquerod and Perrot have found that quartz-glass is freely permeable to helium below a red-heat (Comet.
It does not react with the alkali metals, but combines with magnesium at a low red heat to form a boride, and with other metals at more or less elevated temperatures.
It reduces many metallic oxides, such as lead monoxide and cupric oxide, and decomposes water at a red heat.
It is a white powder, which turns pale yellow on heating, and melts at a red heat.
The pyrites is subjected to dry distillation from out of iron or fire-clay tubular retorts at a bright red heat.