248 METALS. 



to oxide, with a brilliant greenish flame. When zinc 

 is burned in considerable quantity, in a highly heated 

 crucible, the oxide forms flakes in the air, to which the 

 name of lana philosophica, or philosophers' wool, was 

 given by the alchemists. The metal may be melted 

 over a spirit lamp, in an iron spoon. 

 Mention the 613. USES OF ZINC. Zinc is principal- 

 uscs of zinc. \y employed in the form of sheet zinc, for 

 roofing and similar purposes. It is also used, like tin, 

 as a coating to protect iron chains and other objects 

 from rust. The coating is effected by plunging the 

 iron into molten zinc, which forms an alloy upon its 

 surface. The iron thus coated is sometimes called gal- 

 van' zed iron, though without reason, as is evident from 

 the above process. Solutions of zinc are sometimes 

 used to prevent the decay of wood, and to render it 

 less combustible. It has also been employed with 

 success, as a substitute for copper, in sheathing vessels. 



CLASS IV. 



TIN. 



x 



614. DESCRIPTION. Tin is a brilliant 



Describe the . .. .. . _ 



metal Tin. white metal, very soft and malleable, and 

 From what t easily tarnished. When a bar of tin 



ore is it made? * 



is bent, it gives a peculiar grating sound, 

 fancifully called the cry of tin. This is a consequence 

 of the friction of the minute crystals of tin of which 

 it is composed. Its only ore is an oxide, called tin 



