﻿112 



Mr. D. Tyrer 



the 



volume under varying pressures. The following- table gives 

 the values of C^ at different densities (A) of the gas for a 

 mean temperature of 56° C. 



A. 



c. 



A. 



c,_ ; 







0-1650 



0-12 



0-1954 



o-i 



0-1671 



0-13 



0-1974 



0-05 



0-1765 



014 



0-2014 



0-08 



0-1812 



015 



02045 



0-10 



0-1896 







We see again that the specific heat of a fluid at constant 

 volume increases as the density increases, and from this 

 it must follow that in an isothermal change in density, 

 intra-molecular energy is liberated. This result is of extreme 

 importance in the investigation of the potential energy of 

 liquids and molecular attraction. It vitiates at once all 

 conclusions regarding molecular attraction based on the 

 assumption that during the expansion of a liquid the whole 

 of the energy absorbed goes to do work against molecular 

 attraction, except of course the small amount which does 

 work of expansion against the external pressure. 



The intra-molecular energy liberated during expansion 

 will probably be a function of the volume change and of the 

 temperature. We may write this energy F(T, Y x — V). As- 

 suming the simple law of attraction — , the equation (1) 

 for the expansion ot a liquid becomes 

 Wo + FiT^ -V) 



I n— 1 »-l I 



MPT" V 2 TV 



where W is the observed energy change ; and equation (4) 

 becomes 



c„ 



..wfi-g 



C„) + F(T,AV) 



E + F(T,V, 



°s(vTav) 



Vl) 



} 



+ 1. 



Now as the factor F(T, AV) will be negligibly small, it 

 follows that the value of n given in Table II. must be 

 minimum values, L e. the index of the distance of separation 



