MANGANESE, IKON, COBALT, NICKEL, CHROMIUM. 243 



the iron, the oxygen very much so. As about twenty-seven 

 gallons of this gas are used up in forming a pound of rust, 

 it must be vastly condensed to occupy so little space. This 

 remarkable condensation of oxygen takes place in the for- 

 mation of all the solid oxides. 



The third oxide, Fe 3 O 4 , is sometimes considered as a 

 combination of the first and the second oxides, FeO.Fe 2 O 3 , 

 and hence is also called ferroso-ferric oxide. This oxide 

 forms no salts, but it occurs in nature very largely, forming 

 an important ore. This is endowed with magnetic proper- 

 ties. The common loadstone is ferroso-ferric oxide. Its 

 color is black, and many dark and green stones owe their 

 color to it. The celebrated Swedish iron is mostly made 

 from it. The scales thrown off from heated iron by the 

 hammer of the blacksmith are formed of this black oxide. 



339. Meteorites. Abundant as iron is, it is never found 

 in metallic form except in meteorites, and then it is alloyed 

 with nickel and some other metals. In the large meteorite 

 in the cabinet of Yale College, brought from Texas, and 

 weighing nearly two tons, there is from eight to ten per 

 cent, of nickel, the mixture of the two metals not being 

 uniform throughout. 



340. Production of Iron from its Ores. In order to obtain 

 iron from its ores they must be deprived of their oxygen, 

 and of the impurities that are mingled with them. The 

 oxygen is removed by subjecting the ores to intense heat 

 in a furnace with charcoal. This causes the oxygen to 

 leave the iron, and unite with the carbon of the charcoal to 

 form carbonic oxide and anhydride, which fly off. But an- 

 other thing is necessary to remove the impurities, silica, 

 clay, etc. For this purpose limestone is introduced into the 

 furnace, which forms with the impurities a slag or glassy 

 substance, which, as the iron is permitted to run out, floats 

 on the surface of the melted metal, and is raked off. The 



