10 Messrs. Barrell, Thomas, and Young on the 



p 



The ratio — ^ would, of course, vary to some extent during 



2 



the distillation ; the value of the constant, c, does not differ 



p 

 greatly from the mean value of the ratio ^. 



2 



This equation of Brown's may be written in the form 



d% 



= c 



drj 7]' 

 where f = residue of liquid A at any instant, 



V 



Taking L and M as the weights of A and B originally 

 present, and L + M = l, we obtain by integration 



where ?/=quantity of the more volatile liquid A in unit weight 

 of the distillate coming over at the instant when x is the 

 quantity of liquid distilled. 



By means of this equation we may trace the changes of 

 composition that take place in the course of a distillation, 

 and the variation in the composition of the distillate may be 

 represented graphically. 



To take a very simple case, let us suppose that c=2, and 

 tiiatL = M = i. 



Fig. 1. 



0-5 



1HHH1 1H 



■■■■ELI ' 



0-5 



In the diagram (fig. 1) the amounts of distillate that have 



