Half a century later, nitrous oxide came into use as an anesthetic.

As prepared by the reduction of the oxide it is a grey powder.

The metal is chiefly used, as the oxide, for colouring glass and porcelain.

If an air-tight receptacle is not available, a small percentage of powdered carbon is added to the zinc-dust, to prevent increase in the amount of oxide, which, if present in excess, tends to make the deposit dull.

Cobalt monoxide, CoO, is prepared by heating the hydroxide or carbonate in a current of air, or by heating the oxide C0304 in a current of carbon dioxide.