272 SCIENCE PROGRESS. 



and acetic acid, between low temperatures and about 30 

 from their critical points. In the case of methyl and ethyl 

 alcohols the agreement extends even as low as — go°C 

 Agreement near the critical temperature may also be 

 secured by a slight alteration in the formula. Neglecting, 

 for the present, the slight alteration, the constants for these 

 associating substances are : — 



Having found a formula which reproduces the experi- 

 mentally found values of the molecular surface energy of 

 associating liquids at different temperatures, we are in a 

 position to calculate the degree of molecular complexity of 

 the liquid in the following manner. Supposing that the 

 liquid is composed partly of complex molecules and that x 

 is the measure of complexity, we have, as before- 



y (xMvf = 2-121 (t — d), 



or — 



y (Mvf = T X2'I2IX(t-4 



But, according to the formula we have just found — 



7 



( Mr)».iLt^). 



v ; 1 + UT > 



so that by equating the two right-hand sides of the equa- 

 tions and simplifying we get — 



( 2-121 . . "| f 



The degree of association x, of methyl and ethyl alco- 

 hols, water and acetic acid, at different temperatures has 

 been calculated in this way and the results are given in the 

 following table : — 



