370 



APPLIED SCIENCE 



411. Iron Ores. Iron, in the forms of wrought iron, cast 

 iron, and different kinds of steel, is used in the industries and 

 trades more than any other metal. All forms of iron arc 

 obtained from the earth and are found combined in different 

 amounts with other elements and substances which can 

 be separated only by strong heat. In addition to being 

 found as a compound, iron is mixed in all proportions with 

 rock, dirt, etc. 



The most common forms of iron ores are as follows: 

 Magnetite or lodestone (symbol Fe 3 4 ), the richest of all iron ores, 



possesses the prop- 

 erty of attracting 

 to itself- small 

 pieces of iron. 



Hematite (sym- 

 bol 'Fe 2 3 ), the 

 next richest ore, is 

 very abundant in 

 this country. 



Limonite 

 (2Fe 2 O 3 . 3H 2 0), 

 sometimes called 

 FIG. 184. Inspection of Pig Iron. The amount bog-iron ore, is not 

 and kind of pig iron is carefully determined , , 



before it is placed in the cupola. This illustra- a P U1 

 tion shows the inspection of the pig iron before known by the yel- 

 it is dumped into the furnace. Notice the shape i ow streak it pro- 

 duces on porcelain. 



Siderite (FeCO 3 ), called spathic iron ore, contains about 48% 

 of iron. 



412. The Refining of Iron. Since iron is found in a com- 

 bined state and mixed with either sand, lime, or clay and a small 

 percentage of manganese, phosphorus, and sulphur, it is neces- 

 sary to free it of the elements with which it is combined. This 

 process is performed in a blast furnace (Fig. 185). A blast 



