Properties of Liquid Mixtures. k3 



Two other papers on the same subject, which appeared 

 about the same time as my earlier one, call for some notice. 

 These are by C. E. Linebarger (Journ. of Amer. Chem. Soc. 

 vol. xvii.) and by M. Margules ( Wien. Ber. vol. civ.). 



Linebarger made measurements of the vapour-pressures of 

 certain liquid mixtures, and of the way in which the two 

 components shared the pressure between them. He did not 

 attempt to relate his results to the deductions of thermo- 

 dynamics, but merely to obtain empirical generalizations. 

 The method he adopted is at first sight a very promising one, 

 as it allows of the determination of both total and partial 

 pressures in the same experiment ; it consisted in drawing a 

 measured volume of air through the liquid mixture, and 

 analysing by combustion the vapour which the air carried 

 away with it. The method has been applied successfully to 

 find the vapour-pressure of aqueous solutions of low volatility, 

 but it is not so suitable to the present case, as in Linebarger' s 

 experiments the vapour-pressure was sometimes as high as 

 300 mm., and the inaccuracies of if appear to increase out of 

 proportion to the pressure to be measured. Linebarger tested 

 his apparatus by preliminary measurements of pure liquids : 

 finding for instance, for ethyl iodide 199 mm. against Reg- 

 nault's 206, and for chloroform 290'1 against 301/1. This 

 he calls a " most excellent correspondence.^ I tried the 

 method before reading the account of his results, and found 

 similar discrepancies of one or two per cent., so that it can 

 evidently not be regarded as satisfactorily worked out as yet. 

 It has also the disadvantage of being so slow that it is 

 impossible to get numerous data. I have, therefore, pre- 

 ferred to revert to the better known methods, and nearly 

 all the observations mentioned below were taken by the 

 " dynamic ; ' method. 



Linebarger gives an empirical result which may be con- 

 sidered along with the observations contained in this paper : 

 that strictly normal liquids, such as benzene and toluene, 

 have in mixtures a partial pressure simply proportional to the 

 molecular percentage of them present in the liquid. It is 

 important, as on it Linebarger bases a rule for determining 

 the molecular complexity of liquids. To this point we shall 

 have to revert. 



Margules's paper consists only of deductions from the pre- 

 vious experiments of others ; but it includes a theorem given 

 in my paper (loc. cit.) as well as several others ; and in an 

 appendix mentions that all these results have been forestalled 

 in the very systematic thermodynamical studies of Duhem — 



