( 460 ) 



In order to ascertain myself of this I compressed by means of the 

 mercury compressor described in Communication N°. 54 a mixture 

 of about one part of helium and 6 parts of hydrogen in a glass tube, 

 which had a capillary inflow tube at the top, and a capillary 

 outlet tube at the bottom, and which was merged in liquid hydrogen. 



Up to 49 atmospheres the liquid hydrogen was seen to deposit 

 from the gas mixture, bounded by a distinct hollow meniscus against 

 the helium. At 49 atmospheres the helium, or properly speaking 

 the gas phase consisting chiefly of helium, went down just as water 

 through oil, and remained on the bottom as a large drop. With 

 further compression to 60 atmospheres and decrease of pressure to 

 32 atmospheres the volume of the bubble appeared to follow the 

 change of the pressure as that of a gas. At 32 atmospheres the 

 bubble rose again. By changing the pressure the bubble was made 

 to rise and descend at pleasure. 



The closer investigation of these phenomena in connection with 

 the isotherms of helium and the if'-surfaces of H^ and He is an 

 extensive work, so that in anticipation of the results which most 

 likely will be definitely drawn up only much later, I feel justified 

 in confining myself to this sketchy communication. 



One remark may be added now. It appears that the h of helium 

 must be small, from which follows again that a must have an 

 exceedingly small value, because the critical temperature, if it exists, 

 must lie very low. In this direction points also a single determination 

 of the plaitpoint of a mixture of helium and hydrogen which I have 

 already made. Whether a has really a positive value, whether it is 

 zero, or whether (what is also conceivable) a is negative, will have 

 to be decided by the determination of the isotherms of helium. 



(December 21, 1906). 



