290 Prof. K. Olszewski. [Jan. 31, 



III. " The Liquefaction and Solidification of Argon." By Dr. 

 K. OLSZEWSKI, Professor of Chemistry in the University of 

 Cracow. Communicated by Professor WILLIAM RAMSAY, 

 F.R.S. Received January 28, 1895. 



(Abstract.) 



Having been furnished, by Professor Ramsay's kindness, with a 

 sample of the new gas, argon, I have carried out experiments on its 

 behaviour at low temperatures and at high pressures, in order to 

 contribute, at least in part, to the knowledge of the properties of this 

 interesting body. 



The argon with which I was supplied had been dried with phos- 

 phoric anhydride ; its density was 19'9 (H = 1) ; and Professor 

 Ramsay thought that at the outside it might contain 1 to 2 per cent, 

 of nitrogen, although it showed no nitrogen spectrum when examined 

 in a Pfliicker's tube. 



For the first two experiments I made use of a Cailletet's apparatus. 

 As cooling agent I used liquid ethylene, boiling under diminished 

 pressure. 



In both the other experiments the argon was contained in a 

 burette, closed at both ends with glass stop-cocks. By connecting 

 the lower end of the burette with a mercury reservoir, the argon was 

 transferred into a narrow glass tube fused at its lower end to the 

 upper end of the burette, and in which the argon was liquefied, and 

 its volume in the liquid state measured. In these two series of ex- 

 periments liquid oxygen, boiling under atmospheric or under 

 diminished pressure, was employed as a cooling agent. I made use of 

 a hydrogen thermometer in all these experiments to measure low 

 temperatures. 



Determination of the Critical Constants of Argon. 



As soon as the temperature of the liquid ethylene had been lowered 

 to 128'6, the argon easily condensed to a colourless liquid under a 

 pressure of 38 atmospheres. On slowly raising the temperature of 

 the ethylene, the meniscus of the liquid argon became less and less 

 distinct, and finally vanished. 



From seven determinations the critical pressure was found to be 

 5O6 atmospheres ; the mean of the seven estimations of the critical 

 temperature is 121. 



At lower temperatures the following vapour-pressures were re- 

 corded : 



