22 Mr. D. L. Hammick on Surface Energy, 



satisfactory values for the latent heat of vaporization when 

 used in Bakker's equation 



fo+ Tt 



J, v 2 



In other words, X 1? the internal latent heat, is equal to 

 ■M at low temperatures, where may be neglected,. 



v 

 and we have : 



a T I d 



P — 



r v v o 



~ v "6' 



_ 6 or .... x 



or *i = -fi' C 111 -) 



This result has already been arrived at on general grounds 

 (Phil. Mag. xxxviii. p. 240), and it would therefore appear 

 that the internal pressure of a liquid at any temperature T 



is -| = X 1 .-=\ 1 s (s=sp. gr. of liquid). In words, the 



internal pressure of a liquid is equal to the internal latent 

 heat per unit volume, in accordance with the original view 

 of Dupre. 



When vapour pressure is negligible in comparison with 

 internal pressure, we may take the pressure in a liquid 



as K = —„ — \is, whence V ^r? = — 2-s = — 2\^ (in me- 



chanical units). Now V^ v = -= , where /3 is the coefficient 



of variation of the volume of the liquid with internal 

 pressure ; this may reasonably be taken as equal to the 

 compressibility of the liquid. Hence 



i=- 2Ks (iv -> 



(J = mechanical equivalent of heat). 



