51�Թ�

Up to this time metallic calces, and for the most part alkalis and earths also, had been regarded as elementary substances.

Oils dissolve the calces of lead, which, by this means, is the basis of paints, plaisters, &c.

Absorption is increased by the calces or solutions of mercury, lead, zinc, copper, iron, externally applied; and by arsenic, and by sulphur, and by the application of bitter vegetables in fine powder.

The third refers to the great quantity of pure air contained in the calces of metals.

But Cavendish instituted a series of experiments which proved that no fixed air could be obtained from metallic calces.