Vapour-pressure and the Volumes of Vapour and Liquid. 383 



must no longer delay the publication of mine ; and I will take 

 leave to communicate first, in this paper, the general formulae, 

 independent of the nature of the particular substances, and a 

 series of numbers relating to them, reserving for another paper 

 the applications to definite substances, 



§ 2. The formula which, in my treatise on the behaviour of 

 carbonic acid, I constructed for the representation of pressure 

 as a function of volume and temperature, to be annexed to 

 previous formulse set up by other authors, is 



^ = R ^-f^W ; • • • • • C 1 ) 



in which p, v, and T denote pressure, volume, and absolute 

 temperature, and R, c, a, and ft are constants. This formula 

 I first formed for carbonic acid, by a comparison with the 

 results of Andrews's observations ; and I added, as a conjec- 

 ture only, that with a different determination of the constants, 

 without any other alteration, it could be applied also to the 

 other gases. When, however, I made the experiment of ap- 

 plying it to those substances for which extended and reliable 

 series of data of observation exist, especially to steam, I found 

 that to bring about a satisfactory accordance a still further 

 alteration of the formula must be undertaken — which I had 

 previously contemplated when occupied with carbonic acid 

 only, but which at that time I abandoned on account of the 

 uncertainty of the data upon which I had been obliged to base 

 the formula. Namely, in the place of the fraction c/T, occur- 

 ring in the last term, a more general temperature-function, 

 with more indefinite constants, must be put. 



Since the more exact knowledge of the temperature-function 

 is not necessary for the general developments here in the first 

 place contemplated, we will, for the present, content ourselves 

 with indicating it by introducing a new symbol. For the con- 

 venience of the calculations, however, it is advisable not to 

 choose the new symbol simply to put it in the place of the 

 fraction c/T, but to make it represent another quantity con- 

 taining that fraction. For this purpose we will give to equa- 

 tion (1) the following form: — 



p 1 c 



RT - V^a ~ RT\v + (3y ; 



and herein the fraction -^^ may be replaced by — ^ , in 



which 6 shall denote the temperature-function left undeter- 

 mined, of which we may provisionally say only that for T=0 

 it likewise has the value 0, and for the critical temperature it 



2G2 



