1-9-4 Natural Elftory of Copper. [Book VI. 



they are generally of a yellow and brilliant afpect. Cop- 

 per is alfo, in fome fpecimens, found united 'with flate y 

 pitcoal, zinc, and antimony. 



Copper is feparated from its ores by different pro- 

 carles, according to the nature of thofe ores. If they 

 contain much fulphur, after being pounded and wafhed> 

 they are roafted in the open air to difpel the fulphur, 

 which in a great meafure fupplies the want of other 

 fiieL The ore is afterwards roafted once or twice 

 more with wood, and is melted in an open fire into 

 a mafs called a mat of copper. In this ftate it Hill 

 contains a large quantity of fulphur, which the work- 

 men continue to expel by repeated roaftings and fu- 

 fions, till the metal acquires a certain degree of purity, 

 and is called black copper, which is fomewhat mal- 

 kable, but ftill contains fulphur, iron, and generally 

 fome other impurities. In order to clear it entirely 

 ofthefe, the copper is haftily fufed with three times 

 its weight of lead. The lead unites with the copper 

 and expels the iron, and the imperfect metals, which 

 happen to be mixed with the copper, are expelled by 

 cupellation. The copper is afterwards refined, by 

 keeping it heated in crucibles for a confiderable time,, 

 fo that it may throw up all the foreign fubftances it 

 Hill contains in the form of fcoria:. It is examined, 

 from time to time, by_irnmerfing iron rods in it, which 

 become coloured with a fmall quantity of copper, and 

 its purity is judged of by the brilliant rednefs of thefe 

 fpecimens. 



Copper is not fo eafily acted on by the air as iron. 

 In fituations, however, where it is expofed to the action 

 of moift air, k becomes gradually covered with a green 

 ruft or calx, which is fapid and foluble in water. This. 

 ruft never penetrates into the frhftance of copper, but 



fcerris: 



