NOTE ON THE LIQUEFACTION OF HYDROGEN AND 



HELIUM. 1 



By Prof. James Dewar. 



In a paper entitled " The liquefaction of air and research at low tem- 

 peratures," read before the Chemical Society, and published in the 

 Proceedings, No. 158, an account is given of the history of the liquid- 

 hydrogen problem and the result of my own experiments up to the end 

 of the year 1895. The facts are substantially as follows: 



Wroblewski made the first conclusive experiments on the liquefac- 

 tion of hydrogen in January, 1884. He found that the gas cooled in a 

 capillary glass tube to the boiling point of oxygen, and expanded 

 quickly from 100 to 1 atmospheres, showed the same appearance of 

 sudden ebulition, lasting for a fraction of a second, as Cailletet had 

 seen in his early oxygen experiments. No sooner had the announce- 

 ment been made, than Olszewski confirmed the result by expanding 

 hydrogen from 190 atmospheres, previously cooled to the temperature 

 given by liquid oxygen and nitrogen evaporating under diminished 

 pressure. Olszewski, however, declared in 1884 that he saw colorless 

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

 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 appearance of an instan- 

 taneous froth. The following extract from Wroblewski's paper (Compt. 

 rend., 1885, 100, 981) states very clearly the results of his work on 

 hydrogen : 



"L'hydrogene sounds a la pression de 180 atmospheres jusqu'a 190 

 atmospheres refroidi par l'azote bouillant dans la vide (a la tempera- 

 ture de sa solidification) et detendu brusquement sous la pression 

 atmospherique presente une mousse bien visible. De la couleur grise 

 de cette mousse, oil l'oeil ne peut distinguer des gouttelettes incolores, 

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

 l'etat de liquide statique et 1'on 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'obtenu suivant les pression s employees des temperatures de —208° 



'From Journal of the Chemical Society, London, No. CCCCXXVII, June, 1898. 

 Vols. LXXIII and LXXIV, pp. 528-535. 



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