290 M. de la Tour on the [April, 



Article IX. 



An Account of some Results obtained by the combined Action of 

 Heat and Compression upon certain Fluids, such as Water, 

 Alcohol, Sulphuric Ether, and the rectified Oil of Petroleum. 

 By M. le Baron Cagniard de la Tour.* 



It is well known that by means of a Papin's digester, the 

 temperature of fluids may be raised much above their usual 

 boiling point ; and we are led to suppose that the internal pres- 

 sure which increases with the temperature would be an obstacle 

 to the total evaporation of the fluid, especially if the space left 

 above the fluid be not considerable. 



In reflecting on this subject, it occured tome that the expan- 

 sion of a volatile fluid had necessarily some limit, beyond which 

 the liquid, notwithstanding the pressure, must be converted into 

 vapour, little as the capacity of the apparatus allows the fluid 

 to extend beyond its maximum of dilatation. 



In order to verify this opinion, I put some alcohol of spe- 

 cific gravity 0837, and a ball or sphere of quartz, into a 

 small Papin's digester made of the end of a very thick gun 

 barrel ; the fluid occupied nearly one of the apparatus. 

 Having noticed the kind of noise which the ball occasioned 

 while rolling in the cold gun barrel, and afterwards when it was 

 slightly heated, I arrived at a point in which the ball seemed to 

 rebound at each percussion, as if it was no longer surrounded by 

 a fluid in the gun barrel. This effect was best observed by apply- 

 ing the ear to the end of the handle, which served to sup- 

 port the machine ; it ceased upon cooling, and was reproduced 

 when the necessary degree of heat was again applied. 



The same experiment was repeated with water, but with imper- 

 fect success ; for on account of the high temperature which it 

 was necessary to employ, the apparatus could not be perfectly 

 closed. With sulphuric ether and oil of petroleum, the case was 

 different ; they presented the same phenomena as alcohol. 



In order to observe these effects of heat and compression with 

 greater facility, I put the same liquids into small glass tubes 

 closed at one end, and afterwards at the other, by means of the 

 blowpipe. A small piece of glass was fastened to each tube to 

 serve as a handle. 



One of the tubes into which alcohol was introduced so as to oc- 

 cupy nearly two-fi fths of it, was heated with the precautions requi- 

 site to prevent its being broken ; in proportion as the fluid expanded, 

 its mobility became greater; the fluid after having attained 



* From the Annales de Chimie et de Physique, torn. xxi. p. 127. 



