236 Scientific Proceedings, Royal Dublin Society. 



equal unity for a concentration of 95'47, while for higher concentrations 

 K should fall to less than unity. 



From the industrial point of view it is necessary to know, during the 

 purification of the alcohols, the rate at which the impurities are removed 

 with respect to tlie ethyl alcohol. 



If s be the weight of impurities in part of kilogram per kilogram of the 

 original liquid, and S the weight of impurities in 1 kilogram of the mixed 

 vapour, Sorel gives the following relationship : 



^S" = K,s + K,s- + lus' . . . . ; 

 or S = KxS approximately. 



The distillation of mixtures of ethyl alcohol, higher alcohols, various 

 esters, aldehydes, &c., and water over a wide range of alcohol concentration 

 has been made by Barbet.' 

 The ratio 



Percentage of "impurities" in ethyl alcohol in distillate 

 Percentage of " impurities " in ethyl alcohol in liquid 

 he designated by K', and it is known as the coefficient of purification. If 

 , percentage by wfc. of impurities (i.e. amyl alcohol, &c.) in vapour 

 ~ percentage by wt. of impurities (amyl alcohol, &c.) in liquid ' 



then K' = ^- 



The value for IC is dependent largely on the alcoholic concentration of 

 the solution. It indicates how far distillation will remove this impurity 

 from the alcohol, apart altogether from the quantity of water present. This 

 " coefficient of purification " is of more technical value than the coefficient 

 of enrichment. 



Using a similar notation to that employed by the authors in the study of 



the fatty acids,' the K of Sorel may be expressed in a slightly different form 



where 



a = initial amount of alcohol in flask ; 



X = amount of alcohol in distillate after volume v has distilled 



V = constant volume of liquid in flask. 



If p = density of water vapour in the flask, and a = weight of water per 



unit volume of distillate, we have 



concentration in vapour phase x o- 



K 



concentration in liquid phase x p 

 = X F or ^ X F X 2'3026, where ^ = - log 



V " a - a; 



' "La Rectification et les colonnes Rectificatrices," 1895, p. 46. 

 2 §ci. Proc. B.D.S., 1919, xv, 519. 



