178 



Prof. W. Ramsay. The Complexity and the [June 14,. 



It may be remarked that at temperatures within 20 or 30 degrees 

 of the critical point the former no longer accurately expresses the 

 results. This is not peculiar to associating compounds, as has already 

 been shown in the ' Phil. Trans.,' loc. cit., p. 657. Should it be 

 desired to secure more accurate correspondence between the found 

 data near the critical temperatures and those calculated, the last term 

 may be modified. The equation then becomes 



For ethyl alcohol, the value of X is 0'044, and, on introducing this 

 correction, the calculated values near the critical point, above 180, 

 are as follow : 



Similar corrections could be introduced for methyl alcohol, acetie 

 acid, and water, which would have the effect of reproducing the 

 experimental numbers at low values of T. 



The following considerations show how it is possible to calculate 

 the degree of association of such compounds at any desired tem- 

 perature. Neglecting for the present the " X " term, which is intro- 

 duced to secure concordance at temperatures near the critical point, 

 let us consider equation (1), where k has the value 2' 121 for unasso- 

 ciating liquids, viz., 



7 (Mi/)* = 2-121 (T d). 



Supposing that the liquid is composed partly of complex molecules,, 

 and that a; is a measure of the complexity, we should have 



7 (xM.v)% = 2-121 (T d), 



or 



7 (Mt>) = 2-121 X -= X (7 



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