

Properties of a Mixture of Liquids. 401 



and alcohol, (ii) alcohol and ether, (iii) ether and carbon 

 disulphide. Unfortunately for our present purpose only the 

 second and third of these can be regarded as a typical mix- 

 ture, for water is anomalous in many of its properties. 



Secondly, Konowalow* has published measurements of 

 mixtures of water with methyl, ethyl, propyl, and isobutyl 

 alcohols, and formic, acetic, propionic, and butyric acids, 

 which illustrate well the different behaviour of completely 

 and incompletely miscible liquids. 



On the other hand, I am not aware of any measurements 

 of the composition of the vapour rising from a mixture of 

 liquids except those of F. D. Brown f, who considered the 

 point in connexion with fractional distillation. He used 

 carbon disulphide and benzene; but as his method was to 

 determine the composition of successive fractions in a distil- 

 lation at constant pressure, he does not give a table of values 

 of s as a function of g at any one temperature, as is required 

 for our equation (11). He states, however, a general con- 

 clusion as to the composition of the vapour, which may be 

 applied to equation (11), enabling us to integrate it, and his 

 experimental numbers will then suffice to test the accuracy of 

 the integral equation to a certain extent. 



(iii.) Integration of the Thermodynamic Relation, in particular 



Cases. 



F. D. Brown states that t is a constant multiple of q, where 

 (as above) t expresses the ratio of the masses of the two sub- 

 stances in the vapour, q in the liquid. This generalization is 

 confessedly only an approximate one ; and, further, without 

 loss of accuracy the multiple may be taken as the ratio 

 between the saturation-pressures of the two substances. That 



is, 



t = kq; 



or appproximately, 



KB 



We proceed to show that according to our theory, if k is a 

 constant it must have the value — 



Let t = kq, then s—-r-kq, .... (12) 



* Wied. Ann. xiv. pp. 34-51, 219-225 (81). 

 t Journ. Chem. Soc. xxxv. p. 547 (79). 



