2G() ( Ol'I'ER. 



when warmed or rubbed. It is hard, sonorous, ductile, and very 

 malleable. Its specific gravity is about 8*8. It melts at a tempe- 

 rature equal to 27 c of Wedgewood's scale : by a more violent heat 

 it may be made to boil, and to evaporate in visible fumes. It is 

 oxidized when heated in contact with atmospherical air, at a tem- 

 perature far below that of ignition. Many of the acids oxidate it, 

 and render it soluble in water. When exposed to air and moisture, 

 it attracts oxygen, .and a green crust is formed on its surface, which 

 is a carbonate of copper. Fat substances arc said to favour its 

 combination with the oxygen, and to cause it to tarnish and rust 

 more speedily. It combines with phosphorus, and forms, by ad- 

 mixture with other metals, several important alloys. 



Salts of Copper. 



The saline combinations of copper are usually of a blue or green 

 colour. They arc decomposed by the alkalies and earths. Ammo- 

 nia added to the solutions produces a deep blue colour, and the 

 ferro-prussiate of potash a reddish-brown precipitate. A plate of 

 iron or zinc immersed in these solutions is immediately coated with 

 copper. Metallic copper is also obtained when they are exposed 

 to a strong heat along with charcoal. 



Sulphate of Copper, Cupri Sulphas. Ph. — This is the most 

 important of the salts of copper. In commerce it is called blue 

 vitriol, and is generally prepared by roasting copper pyrites, and 

 exposing it in a humid state to the action of air, in which case the 

 metal is oxidized by absorbing oxygen ; at the same time the 

 sulphur is changed into sulphuric acid, and the sulphate of copper, 

 thus formed, is procured by lixiviation and crystalization. The 

 sulphate of copper is in the form of rhomboidal prisms, of a deep 

 rich blue colour. It is inodorous, and has a nauseous metallic 

 styptic taste. It is soluble in four parts of water at GO , and the 

 solution reddens litmus paper. It is insoluble in alcohol. It is 

 decomposed by the alkalies and alkaline carbonates, by the acetates 

 of lead and iron, by the oxymuriate of mercury, nitrate of silver, 

 acetate of ammonia, and tartrate of potass, and is precipitated by 

 all the astringent vegetable infusions. This salt is sometimes 

 prescribed internally as an emetic, in the early stages of phthisis, 



