2 Professor Dewar [Jan. 20, 



drops, and by partial expansion to 40 atmospheres, the liquid hydro- 

 gen was seen by him running down the tube. Wroblewski could 

 not confirm Olszewski's results, his hydrogen being always obtained 

 in the form of what he called a " liquide dynamique," or the appear- 

 ance of an instantaneous froth. Olszewski himself seven years later 

 repeated his experiments of 1884 on a larger scale, confirming 

 Wroblewski's results, thereby proving that the so-called liquid 

 hydrogen of the earlier experiments must have been due to some 

 impurity. The following extract from Wroblewski's paper states very 

 clearly the results of his work on Hydrogen : — 



" L'hydrogene soumis a la pression de 180 atm. jusqu'a 190 atm., 

 refroidi par l'azote bouillant dans la vide (a la temperature de sa 

 solidification) et detendu brusquement sous la pression atmospherique 

 presente une mousse bien visible. De la c >uleur grise de cette 

 mousse, ou l'ceil ne peut distinguer des gouttelettes incolores, on 

 ne peut pas encore deviner quelle apparence aurait l'hydrogene a 

 l'etat de liquide statique et Ton est encore moins autorise a preciser 

 s'il a ou non une apparence metallique. J'ai pu placer dans cette 

 mousse ma pile thermo-electrique, et j'ai obtenu suivant les pressions 

 employees des temperatures de —208° jusqu'a -211° C. Je ne peux 

 pas encore dire dans quelle relation se trouvent ces nombres avec la 

 temperature reelle de la mousse ou avec la temperature d'ebullition de 

 l'hydrogene sous la pression atmospherique, puisque je n'ai pas encore 

 la certitude que la faible duree de ce phenomene ait permis a, la 

 pile de se refroidir completement. Neanmoins, je crois aujourd'hui 

 de mon devoir de publier ces resultats, afiu de preciser l'etat actuel 

 de la question de la liquefaction de l'hydrogene." * 



It is well to note that the lowest thermo-electric temperature 

 recorded by Wroblewski during the adiabatic expansion of the hy- 

 drogen (namely, - 211°) is really equivalent to a much lower tempera- 

 ture 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 obser- 

 vations. In a posthumous paper of Wroblewski's on ' The Compression 

 of Hydrogen,' published in 1889, an account appears of further 

 attempts which he had made to liquefy hydrogen. The gas com- 

 pressed to 110 atmospheres, was cooled by means of liquid nitrogen 

 under exhaustion to —213 "8°. By suddenly reducing the pressure, 

 as low a temperature as —223° on his scale was recorded, but with- 

 out any signs of liquefaction. This expansion gives a theoretical 

 temperatuie of about 15° absolute in the gas particles. The above 

 methods having failed to produce static hydrogen, Wroblewski sug- 

 gested that the result might be attained by the use of hydrogen gits 

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

 Wroblewski devoted his time to a laborious research on the iso- 



* Couipt. Rend. 1885, 100, 981. 



