408 Mr Kleeman, On the Nature of the Internal Work, ete. 
of which corresponds to a different hypothesis. It is evident 
therefore that there is only one way to obtain reliable information 
about the law of molecular attraction from internal heat of evapo-— 
ration data. Any other way might lead to the discovery of 
excellent formulae for the internal heat of evaporation, but could 
by no means give any definite information about the law in 
question. 
I have obtained* in the way described the law 
é = “4 >Vm, 
a eas a ema 
where z denotes the distance of separation of the molecules which 
are at the temperature T, x, that of the molecules in the liquid 
state at the critical temperature, and d (z =) is a function of 
these quantities left arbitrary. The quantity $m, denotes the 
sum of the square roots of the atomic weights of the atoms of a 
molecule; and the attraction of “cohesion” of an atom is thus pro- 
portional to the square root of its atomic weight. Since I have 
shown in this paper that «— wu, is small in comparison with U, the 
deduction of the law is placed on a perfectly sound basis. It is 
evident that each of the definite laws that have been obtained by 
introducing assumptions correspond to certain forms of the arbitrary 
function. This connection has been discussed at length+. It was - 
also deduced} that the function @ does not vary much with z and 
roughly inversely as 7’ from other data than those relating to the 
internal heat of evaporation. 
Note. It will be convenient here to correct two misprints. 
Equation (27) on page 639 of the Proc. Camb. Phil. Soc., vol. XV. 
Pt. 7, should read n= k, ae ; and equation (2) on page 177, 
ce Pe” ‘ 
vol. xvi, Pt. 1, should read 7 = M? (2a) 
(Sey)? 
* loc. cit. and papers quoted therein. 
+ loc. cit., Oct. 1911, pp. 566—586. 
~ loc. cit., May 1910, p. 807; and Proc. Camb. Phil. Soc., xvi. Pt. 6, 1912, 
pp. 553—559. 
