260 LIQUEFACTION OF HYDROGEN AND HELIUM. 



jusqu'a — 211° 0. Je ne peux pas encore dire dans quelle relation se 

 trouvent ces nombres avec la temperature reele de la mousse et la 

 temperature d'ebullition de l'hydrogene sous la pression atmospheri- 

 que, puisque je n'ai pas encore la certitude que la faible duree de ce 

 phenomene ait perinis a le pile de se refroidir coinpletement. ^ean- 

 moins je crois aujourd'hui de mon devoir de publier ces resultats, afin 

 de preciser l'etat actuel de la question de la liquefaction de l'hydro- 

 gene." 



It is well to note tliat the lowest thermo-electric temperature recorded 

 by Wroblewski during the adiabatic expansion of the hydrogen, namely, 

 — 211°, is really equivalent to a much lower temperature on the gas 

 thermometer scale. The most probable value is —230°, and this must 

 be regarded as the highest temperature of the liquid state, or the 

 critical point of hydrogen according to his observations. The above 

 methods having failed to produce "static" hydrogen, Wroblewski 

 suggested that the result might be attained by the use of hydrogen 

 gas as a cooling agent. From this time until his death in the year 1888 

 "Wroblewski devoted his time to a laborious research on the isother- 

 mals of hydrogen at low temperatures. The data thus arrived at 

 enabled him, by the use of Van der Waal's formulae, to calculate the 

 critical constants and boiling point of liquid hydrogen. 



Olszewski returned to the subject in 1891, repeating and correcting 

 his old experiments of 1884, which Wroblewski had failed to confirm, 

 in a glass tube 7 millimeters in diameter instead of one of 2 millimeters, 

 as in the early trials. He says, " On repeating my former experiments 

 I had no hope of obtaining a lower temperature by means of any cool- 

 ing agent, but I hoped that the expansion of hydrogen would be more 

 efficacious, on account of the larger scale on which the experiment was 

 made." The result of these experiments Olszewski describes as 

 follows: "The phenomenon of hydrogen ebullition, which was then 

 observed, was much more marked and much longer than during my 

 former investigations in the same direction. But even then I could not 

 perceive any meniscus of liquid hydrogen.' 1 '' Further, " The reason for 

 which it has not been hitherto possible to liquify hydrogen in a static 

 state is that there exists no gas having a density between those of hy- 

 drogen and of nitrogen, and which might be, for instance, 7-10 (H 1). 

 Such a gas could be liquefied by means of liquid oxygen or air as cool- 

 ing agent and be afterwards used as a frigorific menstruum in the 

 liquefaction of hydrogen." 



Professor Olszewski in 1895 determined the temperature reached in 

 the momentary adiabatic expansion of hydrogen at low temperatures 

 just as Wroblewski had done in 1885, only he employed a platinum 

 resistance thermometer instead of a thermo-junction. 



For this purpose he used a small steel bottle of 20 or 30 cubic centi- 

 meters capacity, containing a platinum resistance thermometer. In 

 this way temperatures were registered which were regarded as those 

 of the critical and boiling points of liquid hydrogen, a substance which 



