132 LIQUID HYDROGEN. 



hydrogen from VM) atmospheres, previously cooled to the temperature 

 given b}^ liquid oxygen and nitrogen evaporating under diminished 

 pressure. Olszewski, however, declared in ISS-t that he saw colorless 

 drops, and by partial expansion to 40 atmospheres the licpiid hydrogen 

 was seen by him running down the tube. Wroblcwski could not con- 

 firm Olszewski's results, his hydrogen being always obtained in the 

 form of what he called a " liquide dynamiipie," or the appearance of an 

 instantaneous froth. Olszewski himself seven years later repeated his 

 experiments of 1884 on a larger scale, confirming Wrol)lewski's results, 

 thereby proving that the so-ealk>d licjuid liydrogen of th(» earlier exjx'ri- 

 ments must have l)een due to some impurity. The following extract 

 from "Wroblewski's paper states very clearly the results of his w ork 

 on hydrogen: 



'•Jyhydrogene soumis a la pression do 180 atm. jusqu'ri lltO atm., 

 refroidi })ar I'azote l)<)uillant dans la vide (a la tiMnperature de sa solidi- 

 fication) et detendu brusipiement sons la pression atmosphei'iiiue pre- 

 sente une mousse ])ien \isible. De la couleur grise de cette mousse, 

 ou I'ijeil ne pent distinguer des gouttelettes incolores, on ne jx-ut pas 

 encore deviner quelle apparence aurait Thydrogene a Tetat de liquide 

 statifiue et Ton est encore moins autorise a preciser s'il a ou non une 

 apparence metalliqu(>. -rai pu placer dans cette mousse ma pile thermo- 

 electrique, et j"ai ol)teMu suivant les pressions employees des tempera- 

 tures de —208 jus({u"a —211^ C. Je ne peux pas encore dire dans 

 quelle relation se trouvent ces nombres avec la temperature reellc de 

 la mousse ou avec la tenqx'raturc d'ebullition de riiydrogenc sous la 

 pression atmospheri(iue. puisque je n"ai pas encore la certitude que la 

 faible durce de ce phenomene ait permis a la pile de se refroidir com- 

 pletement. Neanmoins, je crois aujourd'hui de mon devoir de puhlier 

 ces resultats, afin de ]jreciser Tetat actuel de la (juestion de la liquefac- 

 tion de rhydrogene.'"^ 



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

 by Wroblcwski during the adiabatic expansion of the hydrogen (namel}^, 

 —211°) is reallj" 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 crit- 

 ical point of hydrogen, according to his observations. 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 hj^drogen. The gas compressed to 110 atmospheres, was cooled 

 by means of liquid nitrogen under exhaustion to —213.8°. B}^ sud- 

 denly reducing the pressure, as low a temperature as —223° on his 

 scale was recorded, but without any signs of liquefaction. This expan 

 sion gives a theoretical temperature of about 15° absolute in the gas 

 particles. The above methods having failed to produce static hj^dro- 

 gen, Wroblcwski suggested that the result might l)e attained by the 

 use of hydrogen gas as a cooling agent. From this time until his death, 



^Compt. Eend., 1885, 100, 981. 



