124 IRON. 



salts of the metals themselves, because the oxides of 

 the ordinary metals have no special names, like pot- 

 ash, and soda, &c. ; thus the sulphate of the oxide of 

 lead, for example, is simply called sulphate of lead. 

 When there are two separate oxides of a metal, both 

 of which form salts with acids, that which contains 

 least oxygen is called a protoxide, and that which 

 contains most, a peroxide; the addition of proto or 

 per to the name of a salt, shows whether it is a salt 

 of the protoxide, or of the peroxide ; thus the proto- 

 sulphate or per-sulphate, means a sulphate of the 

 protoxide, or peroxide. 



273. The most widely diffused an^ abundant of all 

 the metallic oxides, as well as that which is the most 

 important and valuable in the arts, is the oxide of 

 iron, which exists in different quantities in a great 

 variety of stones, is very common in soils, and is con- 

 stantly present, though only in small quantity, in 

 the blood of animals, and in the juices of plants. 



274. Iron is very rarely indeed found native in 

 its pure metallic state, but is usually met with in the 

 form of an oxide, either pure or combined with car- 

 bonic acid, and mixed with alumina and silica. Thus 

 the rich black and red iron ores of Cumberland and 

 other places are nearly pure oxide of iron, whilst the 

 common clay iron-stones, as they are called, of Staf- 

 fordshire and Wales, are either carbonate or oxide of 

 iron, mixed with various proportions of alumina and 

 silica. 



275. The important art of smelting iron is entirely 



