THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



JULY 1863. 



I. On the Relation between the Temperature and the Tension of 

 Vapours. By H. Buff, Professor of Physics in the University 

 ' of Giessen*. 



IF a volume of air V, measured under a pressure p, be sud- 

 denly compressed to the volume V, its temperature gradu- 

 ally rises t° above the original temperature t°. 



Suppose this compressed air has, without further change of 

 volume, cooled down to the original temperature t°, it will then 



Y.p 

 have the tension yf = -^y . Let P be the tension of the volume 



V at the temperature t + r, then 



P:^=273 + /+r:273 + f, 



and therefore 



V_P 273 + f 



Y'~p' 273-K + t [) 



If the amount of heat liberated by the compression of the 



variable volume V by -?—= — be the fraction a of that amount 



J 273 + ^H-t 



which the volume V requires to raise its temperature 1° C. with- 

 out a change of volume, we may make 



27Z + t + T :a= - dY ' :dT - 



whence it follows that, when it is remembered that for the value 



V= V the rise of temperature t=0, 



, V , 273 + ^ + t 

 "lo g?7 = log 2?3 + t , 



* Communicated by Prof. Hofmann, F.R.S. 

 Phil. May. S. 4. Vol. 26. No. 172. July 1863. B 



