Cuprous oxide is reduced by hydrogen, carbon monoxide, charcoal, or iron, to the metal; it dissolves in hydrochloric acid forming cuprous chloride, and in other mineral acids to form cupric salts, with the separation of copper.
It dissolves in ammonia with the liberation of nitrogen and the formation of silver oxide, Ag 2 O; and in sulphuric acid forming a fairly stable dark green liquid which, on dilution, gives off oxygen and forms silver sulphate.
It forms crystallizable salts with potassium and calcium hydrates, and functions as a weak acid forming salts named plumbates.
It is not volatile below a white heat, and consequently, if heated with salts of more volatile acids, it expels the acid forming oxide from such salts; for example, if potassium sulphate be heated with boron trioxide, sulphur trioxide is liberated and potassium borate formed.
It is a monobasic acid forming salts which are permanent in air, but which are gradually oxidized in aqueous solution.