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XV. On the Theoretic Determination of Vapour-pressure and 

 the Volumes of Vapour and Liquid. By Prof. R. CLAUSIUS*. 



{Second Paper].) 



§ 1. TN the first paper on this subject, I formed for the de- 

 J- termination of the pressure of a gas as a function of 

 the temperature and volume the following equation, which is 

 a generalization of that which I had previously employed for 

 carbonic acid: — 



p 1 27Q + /3) m 



RT v-u Sd(v + /3) 2 w 



Herein p denotes the pressure, v the volume, and T the abso- 

 lute temperature — namely the sum 273 + £, if t represents the 

 temperature reckoned from the usual zero-point. Further, R 

 is the constant which already occurs in the usual expression 

 of Mariotte and Gay-Lussac's law; and a. and/3 represent two 

 other constants, the sum of which will further on be denoted 

 by y. 6 signifies a temperature-function which for T = has 

 the value 0, and for the critical temperature the value 1, but 

 otherwise is provisionally to be left undetermined. 



It is self-evident that we can give this equation a simpler 

 form if we combine the temperature-function with the con- 

 stant factors occurring in the term into one symbol. Namely, 

 if we put 



27(« + / d) 27y' W 



the equation is changed into 



RT v-u ®(v + /3f W 



The relation between the temperature-function in this 

 equation and that employed above, 6, becomes particularly 

 evident when it is borne in mind that the value assumed by fe) 

 for the critical temperature, and which may be denoted by ® c 

 is to be determined by putting the value 1 for 6 in equa- 

 tion (2). Thence, namely, we get 



8 

 < = 2V (4 > 



* Translated from a separate impression, communicated by the Author, 

 from Wiedemann's Annalen, 1881, vol. xiv. pp. 692-704. 



t For the first paper see Wiedemann's Annalen, xiv. p. 279; trans- 

 lated in the ' Philosophical Magazine ' for December 1881, vol. xii. p. 381. 



