128 PYRITES, OR SULPHURET OF IRON. 



separate the sulphur completely from the Iron, and 

 the native oxides and carbonate are far more con- 

 venient sources of the metal. 



284. Pyrites, or sulphuret of iron, is, however, 

 a substance of considerable importance in the arts, 

 being one of the sources of sulphur, which is ob- 

 tained by heating pyrites in an oven, so constructed 

 that the sulphur, which is expelled in the state of 

 vapor from the pyrites, is cooled and condensed 

 into the solid form in a different part of the oven. 



285. Pyrites, when exposed to the air, soon crum- 

 bles down, and undergoes a very curious change, in 

 consequence of absorbing and combining with oxygen. 

 Both the iron and the sulphur combine with oxygen, 

 and form oxide of iron and sulphuric acid ; and hence 

 the result of this action is sulphate of iron, or com- 

 mon green vitriol, a salt much used in the arts for a 

 variety of purposes. 



286. Pyrites is most abundantly found in the form 

 of variously-shaped balls imbedded in chalk; to 

 which the common name of "thunderbolt" is very 

 improperly applied. As the chalk-hills on the sea- 

 side graduj^Uy wear away, from the action of the sea 

 and weather, these balls of pyrites get exposed to 

 the air, and fall down on the beach, whence they are 

 collected for the use of manufacturers. Many springs 

 of water contain a small quantity of iron, in conse- 

 quence of which they have a peculiar inky taste; 

 this is usually derived from the gradual oxidation of 



