IRON. 105 



sesses the property of being welded; that is, of 

 having two separate pieces united together by 

 hammering when red hot. It is one of the most 

 infusible of the metals, but may by intense heat be 

 melted and run into moulds. It is in its pure state 

 among the hardest of the metals, but may be made 

 to exceed all the rest in hardness when converted 

 into steel. 



It possesses the magnetic property, the load' 

 stone itself being an ore of iron. 



Exposed to the action of the air and moisture, 

 iron soon rusts or OTidates. It then attracts the 

 oxygen and carbonic acid, and is changed into a 

 reddish brown substance, which is a mixture of 

 oxide of iron and carbonate of iron. 



Iron unites to oxygen in two proportions. The 

 protoxide of iron consists of one hundred parts of 

 iron, and twenty-nine parts oxygen ; it is of a 

 black colour ; hence it is called the black oxide of 

 irony formerly martial ethiops. It is formed when 

 iron is heated red hot ; scales form on the outside, 

 which fly off when hammered. It is magnetic. 



The peroxide is red, and consists of one hundred 

 parts iron, and forty-three oxygen ; it is called the 

 red oxide of iron. The red oxide is formed by 

 keeping iron filings red hot in an open vessel, and 

 agitating them constantly till they are converted 

 into a dark red powder, formerly called saffron of 

 Mars. 



Iron is acted on by all the acids, and various 

 salts of iron are formed : the most remarkable are 

 the following : — 



Sulphate of irony formerly called copperas or 

 green vitriol. 



Nitrate of iroUy and acetite of irdiiy used in 

 dying. 



