Cupric Oxide

Cupric Oxide (copper monoxide, black oxide), $\backslash text\{CuO\}$, is the scale or rust of copper which peels off the surface of the metal when heated. It is got for chemical purposes by heating nitrate of copper to redness in a crucible with occasional stirring, and carefully avoiding any possible admission of coaly matter. By the use of cupric oxide Liebig established the method by which the composition of all organic substances has been determined, as it readily gives up its oxygen at a red heat to carbon and hydrogen, converting them, respectively, into carbonic acid and water, from the weight of which the composition of the organic body is calculated. This oxide is used for staining glass, to which it imparts a green colour; and its solution in ammonia has the remarkable property of dissolving cotton fibre. The Hydroxide, $\backslash text\{Cu\}(\backslash text\{OH\})\_2$, is obtained as a blue precipitate by adding caustic soda to sulphate, or other salt, of copper, which, as in the case of the cuprous oxide, becomes anhydrous on boiling, the blue precipitate becoming black and granular. The salts of cupric oxide are readily obtained by dissolving it in the necessary acids; for example, in sulphuric acid for the sulphate, and in nitric acid for the nitrate of copper.