254 PROFESSOR K. OLSZEWSKI ON THE 
ends with glass stop-cocks. By connecting the lower end of the burette with a 
mercury reservoir, the argon was transferred into a narrow doubly bent glass tube 
connected with the upper end of the burette, and in which the argon was liquefied, and 


ot 
to a mereury air pump 


Mercury reservotr 

clund up shiv ayy 07 5 
Li quiet Oxygei 
Argon to be liquefied. 


its volume in the liquid state measured. In these two series of experiments 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 
ineasure 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 at the following temperatures and 
corresponding pressures :— 
