﻿Internal Pressure of a Liquid. 957 



This is quite obvious from the numerous attempts to correct 

 it or to deduce another equation. I will mention only 



Boltzmann's deduction, that C = C^t 5 and the equation in 

 the form given by Lorentz: 



( ?+ /fflW 1+ A,I). 



Hence it follows, that the proposition of Mr. McC. Lewis 

 that " internal work and internal energy can be treated with 

 respect to one another in the same way as external work and 

 internal energy " * is, perhaps too risky — of which the author 

 was, however, quite aware when saying " it must be remem- 

 bered, however, that thermodynamic work terms are essen- 

 tially external work terms "f- 



By trying to give a physical meaning to each member of 



equation (1), it results that — T ( ^— , j expresses the excess 



of kinetic energy of the molecules of vapour over the liquid 

 ones at the same temperature, which, however, may appear 

 doubtful. We cannot assume any other meaning, K being 

 " le travail total de desegregation,'' provided Mr. McC. Lew T is 

 follows Dupre's idea. It is also doubtful whether " the 

 equality [of the internal energy change to internal work] 

 would only hold good if K were independent of temperature" "f . 

 Dupre says § : "Ainsi le travail restant a accomplir pour separer 

 completement les molecules a temperature constant est en 

 raison inverse du volume; son expression general est le 

 produit de Pinverse du volume par une fonction de la tempe- 

 rature settle "||, and gives the following equation: 



(282) X=p(« 1 -t ?s ) + K-K , f, 



where X is latent heat of vaporization (per 1 gr.), p(v\ — ?* 2 ) 

 external work, and K. K' total work of disaggregation in the 

 liquid and gaseous states. 



Yours faithfully, 

 Laboratory of Physical Chemistry, W. SuKHODSKI. 



Polytechnical Institute, 

 St. Petersburg-, Russia. 



* Trans, of Faraday Soc. vii. p. 1 13. 



t Ibid. p. 96. 



j Phil. Mag-, xxii.p. 104. 



§ Ann. de Chim. et Phys. 4 ser. vol. vi. (1805) p. 280. 



I! Cf. Phil. Mag-, xxii. p. 193. Dupre" virtually assumed K independent 

 of temperature. 



H Ann. de Chim. et Phys. vol. vi. p. 283. I write it 3n the modern 

 designations. 



