in vacuo and in Gases. 



17 



First class. — Binary mixtures of volatile substances which 

 exercise no sensible solvent action upon each other. 



The number of binary mixtures of this class which may be 

 experimented upon with certainty is much more restricted than 

 might be supposed at the first glance, since one essential con- 

 dition in experiments of this kind is, that the substances em- 

 ployed must be perfectly pure, and they must also both be suffi- 

 ciently volatile to enable their individual tensions and that of 

 their mixture to be determined with the necessary exactness. 

 Lastly, it is probable that there ai'e in reality no two volatile 

 substances which are absolutely exempt from those reciprocal 

 molecular actions which produce the phsenomenon of solution. 

 Everyone knows that water which has remained for a consider- 

 able time in contact with essential oils, which are considered 

 insoluble, acquires a very distinct odour of these substances, 

 without its being possible to detect the mechanical interposition 

 of the smallest particle of essence. 



The only mixtures of this class upon which I have operated 

 are, — 



The mixture of water and sulphuret of carbon. 



The mixture of water and chloride of carbon, C 2 CI 6 . 



The mixture of water and benzine. 



The following tables give the results which I have obtained. 

 With regard to each temperature at which an observation has 

 been made, we find the elastic force of the vapour given by the 

 mixture ; the elastic forces of the vapours of each of the sub- 

 stances separately, taken upon the curves of which I have previ- 

 ously given the elements, or which I have determined directly 

 for this purpose ; and lastly, the sum of the two individual elastic 

 forces. 



Phil. Mag. S. 4. Vol. 9. No. 5G. Jan. 1855. 



