ABSOLUTE TEMPERATURE. 105 



p' ~ 460 + t" 



in which p and p' are the pressures corresponding to the 

 temperatures t and t' of a given mass of gas, the volume 

 being constant. 



COR. 5. Since the volume of a given mass of air varies 

 inversely as its density, we have, from (4) and (8), 



+ a p 



*M_+e m P 



%60+7 /' 



where v' and v denote the volumes of a given mass of air at 

 the temperatures t' and t. 



EXAMPLES. 



1. If the pressure of a given mass of gas be 29.25 inches, 

 at the temperature 56 F., what will it become if heated to 

 300 F., the volume being constant? Ans. 43.081 inches. 



2. If 200 cubic inches of gas at 60 F. , under a pressure 

 of 30 inches of mercury, be raised in temperature to 280 F., 

 while the pressure is reduced to 20 inches, find the volume. 



Ans. 426.9 cubic inches. 



55. Absolute Temperature If we can imagine the 

 temperature of a gas lowered until its pressure vanishes, 

 without any change of volume, we arrive at what is called 

 the absolute zero of temperature, and absolute temperature 

 is measured from this point.* 



Let / represent this temperature on the Centigrade 

 scale; then (3) of Art. 54 becomes 



* Besant's Hydromechanics, p. 118. 



