584 Dr. R. D. Kleeman on Molecular Attraction 



Consequences of an Even Distribution of Matter in Space. 



In previous papers the writer* has deduced formulas on 

 the supposition that matter does not consist of molecules but 

 is evenly distributed in space. On making the additional 

 supposition that the internal heat of evaporation consists only 

 of the work done against the attraction of the elements of 

 matter upon one another, it was shown, for example, that 

 I J i/3i = P / «i^ where P %1 is the intrinsic pressure of the liquid 

 and Lj the internal heat of evaporation of unit mass into a 

 vacuum. At low temperatures, when the density of the 

 vapour is small in comparison with that of the liquid, L x is 

 the ordinary heat of evaporation. The result is independent 

 of the law of attraction between the elements of matter. The 

 subject will be extended in this paper. 



From the above result it follows that the heat of evapora- 

 tion is given by the expression f— 1 — — 2 ), where P W2 



denotes the intrinsic pressure of the saturated vapour and p 2 

 its density. If we put P W2 = ^P W1 and substitute the above 

 expression in Clapeyron's equation we obtain 



At the critical point x becomes equal to unity and the equa- 

 tion becomes P nc =^— T e ^, where P Wc denotes the intrinsic 



pressure at the critical point. Now we have seen in a 

 previous part of the paper that at the critical point 



and thus P nc = — 6*5 p c . 



The above expression for the intrinsic pressure may be 

 written in a different form. The attraction between two 

 elements of matter dz may be written p 2 W(dz) 2 . </>(.i\ T), 

 where x is the distance of separation of the elements, p the 

 density of the matter, and W a constant depending on its 

 nature. The expression for the internal heat of evaporation 

 given in a previous paper f now becomes WKp, where K is 

 the same for all matter. If K is constant, that is, if the 

 attraction does not depend on the temperature, the intrinsic 

 pressure may be written Zp 2 , where Z depends only on 

 the nature of the liquid. Nov/ the intrinsic pressures 



* Phil. Mag. June 1910, p. 840, and Oct. p. 665. 

 t Loc. cit. 



