1894.] 



Dissociation of the Molecules of Liquids. 



179 



Comparing this with equation (5), which reproduces the results for 

 associating liquids with fair accuracy, 



it is evident that x corresponds to the expression 



>}' 



It is, of course, easy to include the " X " term, when x follows, as 

 before. 



There can, I think, be no doubt that this method gives a correct 

 value to the factor of association, within certain limits. These limits 

 are conditioned by the fact that the number chosen for &, viz., 2*121, 

 is not absolutely constant, but varies with the nature of the com- 

 pound. The extreme variation found for the fourteen substances 

 which have been most carefully investigated is between 2'020 for ethyl 

 formate, and 2'248 for methyl isobutyrate. On the assumption that 

 this is the extreme divergence, there may be an error of 5 per cent, in 

 a negative or positive direction caused by assuming the mean value 

 2-121. 



But there is another assumption involved in such calculations. It 

 is that a mixture of two liquids possesses such a molecular surface- 

 energy that the mean molecular weight of the mixture, calculated 

 from the proportion in which they are present in the mixture, shall 

 be deducible from the molecular surface-energy. It is conceivable 

 that the surface of such a mixture should not exhibit the same dis- 

 tribution of molecules as the interior, and evidence is required to 

 show that the assumption that it does is correct. This evidence is 

 riven in another communication, and it appears therefore that the 



ssumption is justified. 

 With these premises, therefore, I proceed to give the molecular 



ssociation of methyl and ethyl alcohols, water, and acetic acid. 



N 2 



