SOME CHEMISTRY OF EVERYDAY LIFE 205 



Steel in general is iron containing somewhat more carbon than 

 wrought iron but less than cast iron, the per cent varying according 

 to the uses to be made of the steel and the properties it necessarily 

 must have. 



The "tempering" of steel by workmen skilled in the art through 

 experience consists primarily in securing a desired degree of flexibility, 

 elasticity, tenacity, and hardness. These properties are varied by the 

 extent and rate of temperature changes ta which the metal, and the 

 cohesive force acting between its molecules, is subjected. 



