CHEMISTRY AND HEAT 



59 



into other forms of energy. The equivalent of 1 B. T. U. in 

 foot-pounds is 778 ft.-lb., and this value, 778 ft.-lb., is termed 

 the mechanical equivalent of heat. It is the number of foot- 

 pounds of mechanical energy that would be produced by 

 transforming 1 B. T. U. without any losses. 



COEFFICIENTS OF EXPANSION FOR VARIOUS 

 SUBSTANCES 



Substance 



Coefficient of Linear 



Expansion in Inches per 



Degree F. 



Aluminum 



Brass '. 



Brick 



Cement and Concrete { ro 



c PP er 



Glass 



Gold 



Granite 



Iron, cast 



Iron, wrought 



Lead 



Marble 



Masonry 



Mercury 



Platinum 



Porcelain 



Sandstone { fro 



Steel, untempered 



Steel, tempered 



Tin 



Wood, pine 



Zinc... 



.00001140 

 .00001040 

 .00000306 

 .00000550 

 .00000780 

 .00000961 

 .00000399 

 .00000521 

 .00000841 

 .00000460 

 .00000587 

 .00000677 

 .00001580 

 .00000400 

 .00000206 

 .00000490 

 .00003334 

 .00000494 

 .00000200 

 .00000400 

 .00000670 

 .00000599 

 .00000702 

 .00001160 

 .00000276 

 .00001634 



Latent Heat. The heat expended in changing a body from 

 the solid to the liquid state, or from the liquid to the gaseous 

 state, without change of temperature, is called its latent heat. 



The temperature at which a body changes from a solid to 

 a liquid state is called its temperature of fusion, or its fusing 

 point; and the number of B. T. U. required to effect this change 

 in a body weighing 1 Ib. is called its latent heat of fusion. The 



