582 COPPER. 



dissolves by fusion in a vitreous flux, and produces a green 

 glass. 



Thenard obtained a higher oxide of copper, CuO 2 , by the 

 action of diluted peroxide of hydrogen on the hydrated prot- 

 oxide. 



Chloride of copper, CuCl + 2HO, is obtained by dissolving 

 the black oxide in hydrochloric acid. Its solution, when con- 

 centrated is green, but the salt forms blue prismatic crystals, 

 which contain two atoms of water. It combines with chloride 

 of potassium, and more readily with chloride of ammonium, 

 forming the double salts, KCl + CuCl + 2HO, and NH 4 C1 + 

 CuCl + 2HO. 



Carbonates of copper. When a salt of copper is precipitated 

 by an alkaline carbonate, a hydrated subcarbonate is produced, 

 containing 2 eq. of oxide of copper to 1 eq. carbonic acid. It is 

 a pale blue bulky precipitate, which becomes denser and green 

 when treated with boiling water. It is used as a pigment, and 

 known as mineral green. The beautiful native green carbonate 

 of copper, malachite, is of the same composition, CuO, CO 2 + 

 CuO, HO. The finely crystallized blue copper ore is another 

 subcarbonate. It may be represented as the neutral hydrated 

 carbonate of copper, in combination with a similar carbonate of 

 copper, in which the constitutional water is replaced by oxide 

 of copper : 



jCuO,co 2 +HO 



[CuO,C0 2 + CuO. 



In the green carbonate, the constitutional water of the neutral 

 carbonate of copper is replaced by hydrate of copper. The 

 neutral carbonate of copper itself, of which the formula would 

 be CuO, CO 2 + HO, is unknown. 



Sulphate of copper, Blue vitriol, CuO, SO 3 , HO+4HO; 

 996.9 + 562.5 or 79.88+45. This salt may be formed by dis- 

 solving copper in sulphuric acid diluted with half its bulk of 

 water with ebullition, when the metal is oxidated with formation 

 of sulphurous acid. But the sulphate of copper is more gene- 

 rally prepared, on the large scale, by the roasting and oxidation 

 of sulphuret of copper. It forms large rhomboidal crystals of 

 a sapphire blue, containing 5 eq. of water, which lose their 

 transparency in dry air : they are soluble in four times their 

 weight of cold, and twice their weight of boiling water. Like 



