CHAPTER XXI 



Copper, Zinc, Lead, Tin, Arsenic, Mercury, and 

 Their Compounds and Alloys. 



187. Commercial Importance. The compounds of 

 copper, zinc, lead, tin, and arsenic, while they do not 

 enter into the composition of either plant or animal 

 bodies, are of value in agriculture because of their pres- 

 ence in many useful materials. 



188. Occurrence of Copper and Its Hetallurgy. This 

 element is found in the free state and also in combination 

 with oxygen as CuO and Cu 2 O, with sulfur as Cu 2 S, and 

 with iron and sulfur as copper pyrite, Cu 2 S.Fe 2 S 3 . The 

 ores of copper are first roasted, and if iron is present in 

 large amounts, it is removed as a silicate. The "matte," 

 as it is called, thus produced is subjected to further re- 

 fining. Copper is also produced by electrolysis. 



189. Copper Sulfate. This salt is used the most ex- 

 tensively of any of the copper compounds and is produced 

 by the action of sulfuric acid upon either metallic copper 

 or its sulfid. It crystallizes with 5 molecules of water of 

 crystallization. It is commonly called blue vitriol, and 

 is extensively used in the preparation of pigments, for the 

 preservation of wood, for copper- plating and for the 

 treatment of fungus diseases in plants as in the Bordeaux 

 mixture where it is the principal ingredient. 



Experiment 34. Dissolve 6.2 grams of copper sulfate and 3.50 

 grams of sodium potassium tartrate in 100 cc. of water. Dissolve 

 a small amount of glucose (o.i gram) in 5 cc. of water, add 5 cc. 



