CHAPTER XX. I 



COPPER, MERCURY, SILVER AND ALUMINIUM. 



COPPER (Cu) is a reddish, malleable, ducile metal found abund- 

 antly in nature as native copper, and as an ore combined with 

 sulphur and iron. Copper is used for coins in all parts of the 

 world, and is an ingredient of most of the gold and silver coins, 

 giving them additional hardness. Brass is an alloy of copper, 

 tin and zinc; bell metal and gun metal are alloys of copper and 

 tin, and aluminium bronze consists of 90 parts copper and 10 

 parts of aluminium. Hard solder contains equal parts of cop- 

 per and zinc. Copper is extensively used as a protection for 

 wooden ships; copper wire of different sizes is the substance gen- 

 erally used in transmitting electricity for power and lighting 

 purposes. As copper is found pure, or nearly so, in nature, it 

 was one of the earliest metals worked by man. The early inhab- 

 itants of America made cutting tools and ornaments of copper. 



In Europe and the east brass or bronze was extensively used 

 for many purposes before the discovery of methods for working 

 iron. While iron has supplanted copper in many places, it still 

 remains one of the most useful and valuable of the metals. 

 Copper sulphate (CuS0 4 -f-5H 2 0), blue vitriol, is largely used by 

 the dyer and calico printer, and in the manufacture of pigments. 

 It is also used in electrotyping, in galvanic batteries, and in 

 medicine. When heated the crystals lose their water of crys- 

 tallization, crumbling down to a whitish powder, which again 

 becomes blue when allowed to combine with water. 



Copper is precipitated from the solutions of its salts by the 

 metals zinc and iron and by the galvanic current. If a strip of 

 zinc is placed in a solution of copper sulphate it will soon become 

 covered with a layer of copper, the zinc displacing the copper in 

 the sulphate as follows : Zn-f-CuS0 4 =ZnS0 4 in solution -j-Cu as a 

 (158) 



