iii vacuo and in Gases. 9 



The general tendency of these experiments is to show that the 

 elastic force of vapour of aether in the air is constantly weaker 

 than in vacuo. The absolute difference is greater than with 

 water, and increases with the elastic force itself. 



The experiments which I have made with sulphuret of carbon 

 and benzine lead to the same result. The difference between 

 the elastic force presented by the same vapour in the air and in 

 vacuo, diminishes in proportion to the volatility of the liquid, as 

 may be seen from the following tables : — 



In order to investigate this same subject, I have employed a 

 method which presents many advantages over the preceding. It 

 allows us to study with precision the influence exerted upon the 

 elastic force of the vapour by the total pressure of the gaseous 

 atmosphere which acts upon the volatile liquid, and the quantity 

 of liquid in excess by which the walls of the vessel are moist- 

 ened. For this purpose I made use of the eudiometer which I 

 applied to the analysis of gases, and which is described in the 

 Annales de Chimie et de Physique, vol. xxvi. p. 333. 



I replaced the measuring tube of this apparatus, which usually 

 consists of a glass tube traversed by two platinum wires, by 

 another glass tube which was not furnished with wires, and 

 which was graduated in centimetres so as to indicate the volume 

 of gas. Into this tube the gas in which the volatilization was 

 to be effected was introduced, with the precautions indicated in 

 the memoir just quoted; then, keeping the bath which sur- 

 rounded the apparatus constantly at a temperature of 7 0, 7 C, 

 which was very near that of the surrounding atmosphere, the 

 elastic force presented by this dry gas was determined by the 



