in vacuo and in Gases. 



13 



Tensions of the vapour of aether in carbonic acid gas. 

 Temperature 7°-7 C. 



In these experiments I have noted the precise moment when 

 the vapour began to be deposited in drops on the walls of the 

 tube. I have constantly found that the vapour is then still far 

 from possessing the elastic force of 260 millims., which it pre- 

 sents in vacuo. If the compression of the gas be continued, the 

 condensed liquid becomes more abundant and the tension of the 

 vapour increases, approaching more and more to that observed 

 in vacuo. But an equality is not attained until a thick stratum 

 of liquid has collected on the surface of the mercury. Moreover 

 this equality is only to be observed immediately after the reduc- 

 tion in volume, for the tension afterwards diminishes, and this 

 decrease continues to progress for several hours, although the 

 temperature may be carefully maintained. 



The explanation of these various facts appears to me to be very 

 simple. When a volatile liquid in a limited space is in contact 

 at the same time with a gas which fills this space and with the 

 substance of which its walls are composed, it has a tendency to 

 produce vapour until the tension of the latter shall be equal to 

 that acquired by the vapour in vacuo at the same temperature. 



