CHAPTER XLIII 

 COPPER AND MERCURY 



IN this chapter we encounter the first metals (if we except As 

 and Sb) which are below hydrogen in the activity list, and do not 

 displace that element from dilute acids. Copper and mercury 

 both have two valences, so that we have cupric-ion Cu++ and cu- 

 prous-ion Cu + and mercuric-ion Hg^ 4 * and mercurous-ion Hg + . 

 All the soluble compounds of both are poisonous. 



COPPER Cu 



Occurrence. Copper occurs free in considerable amounts, 

 particularly on the Michigan shore of Lake Superior. Cuprous 

 oxide Cu 2 and basic carbonates, like malachite CuC0 3 ,Cu(OH) 2 , 

 are less common. The latter is often used as an ornamental stone. 

 A large proportion of commercial copper is obtained from chal- 

 copyrite Cu 2 S,Fe 2 S 3 . 



Metallurgy. The free copper, after being concentrated 

 (freed from >gangu). by washing, is 'smelted with a flux.^. The p 

 carbonate is roasted, leaving the oxide. The oxides are reduced 

 with coal. 



The sulphide ores are more difficult to reduce, and the presence 

 of so much iron complicates the process. They are first roasteo^ 

 This removes much of the sulphur as sulphur dioxide, leaving 

 Cu 2 and Fe 2 3 . Next the roasted material is treated in a blast 

 furnace, along with " green " (unroasted) ore, sand (if silica is not 

 present in the ore), and coke. Some of the iron is oxidized and 

 removed in the slag (as silicate). The product, known as copper 

 " matte," is a mixture of cuprous sulphide Cu 2 S with ferrous sul- 

 phide FeS. The third stage is to bessemerize the melted matte 



510 



u Vj^A-y 



