144 AGRICULTURAL CHEMISTRY 



than cast iron, but more than wrought iron. It is pre- 

 pared by oxidizing the impurities of iron by means of a 

 blast of hot air. This is accomplished by heating the 

 cast iron in converters and then forcing through it a blast 

 of hot air which oxidizes the larger portion of the im- 

 purities. By adding cast iron, steel containing almost 

 any desired amount of carbon can be obtained. Iron and 

 steel wire are made by drawing rods through hardened 

 steel plates, the material being properly tempered during 

 the operation. The thin coat of oxid formed on the sur- 

 face is removed by dipping the wire into a bath of dilute 

 sulfuric acid. 



182. Rusting of Iron. Iron in all of its forms readily 

 undergoes oxidation and rusting, due to the joint action 

 of oxygen and water which results in the production of 

 a basic oxid of iron. When the surface of iron is pro- 

 tected, as by painting, oxidation and rusting are pre- 

 vented. When iron is heated to its kindling temperature, 

 it readily oxidizes as in Experiment i . In the welding 

 of iron, oxidation is prevented as far as possible by ma- 

 nipulation and occasionally by the use of materials, as 

 borax, to remove the thin coating of oxid. Iron is read- 

 ily acted upon by all acids, forming a large number of 

 salts. 



183. Iron Compounds. Iron forms two series of salts : 

 ferrous and ferric. Ferrous sulfate, FeSO 4 , commonly 

 called copperas, is used most extensively of any of the 

 iron salts especially for the dyeing of cloth, and to some 

 extent as a disinfectant. 



Experiment 30. Dissolve 0.5 gram of ferrous sulfate in 20 cc. of 



