6 2 o THE POPULAR SCIENCE MONTHLY. 



same phenomenon is observed in releasing carbonic acid, and pro- 

 toxide and bioxide of nitrogen, which have been subjected to strong 

 pressure." 1 



After having obtained these results, at a session of the Academy 

 on December 31st, M. Cailletet announced that he had won a com- 

 plete victoiy over the other permanent gases. M. Dumas informed 

 the members present at the session that the able experimenter had 

 succeeded in liquefying nitrogen, atmospheric air, even hydrogen itself, 

 which would seem to have been the most refractory gas of them all. 



We take from the Comptes JRendus the following details : 



Nitrogen. Pure or dry nitrogen, compressed under about 200 atmospheres, 

 at a temperature of nearly +13 Cent., and then suddenly released, becomes 

 very clearly condensed. There first appears a body resembling a pulverized 

 liquid, in drops of appreciable volume, and then this liquid gradually disappears 

 from the walls of the tube toward the middle, at length forming a sort of verti- 

 cal column in the axis of the tube; this phenomenon persists for more than 

 three seconds. These appearances remove all doubt as to the true character of 

 the phenomenon. M. Cailletet first made this experiment at home with a tem- 

 perature of 29 Cent. ; he repeated it again and again at the laboratory of the 

 Normal School, in the presence of several men of science. 



Hydrogen. Hydrogen has always been regarded as the most refractory of 

 gases, owing to its slight density, and the almost complete conformity of its 

 mechanical properties to those of the perfect gases. Hence it was with very 

 little hopes of a favorable result that M. Cailletet subjected this gas to the same 

 tests which had produced liquefaction of all the others. 



"In my early experiments," says he, "I recognized nothing that was pecul- 

 iar ; but, as often happens in the experimental sciences, the habit of observing 

 phenomena at last leads us to recognize peculiarities where before they were 

 quite unnoticed. This was what happened in the case of hydrogen. On repeat- 

 ing my experiments to-day, December 31st, in the presence and with the assist- 

 ance of Messrs. Berthelot, H. Sainte-Claire-Deville, and Mascart, I succeeded in 

 observing signs of the liquefaction of hydrogen, which to these expert witnesses 

 appeared to be unquestionable. 



"The experiment was repeated many times. Hydrogen placed under a 

 pressure of 280 atmospheres, and then released, becomes transformed into an 

 extremely fine and subtile mist, suspended in the tube throughout its entire 

 length, and then suddenly disappearing. The production of this mist, despite 

 its extreme subtilty, appeared to be indisputable to all the scientific men who 

 witnessed this experiment, and who carefully repeated it again and again, under 

 such conditions as to leave no doubt as to the fact." 



Air. "Having liquefied nitrogen and oxygen, the liquefaction of atmos- 

 pheric air was ipso facto demonstrated. Nevertheless, I concluded to make 

 this a matter of direct experiment ; and here, as might have been expected, I 

 was perfectly successful. I need not say that the air had been first dried and 

 deprived of every trace of carbonic acid. In this way," adds M. Cailletet, "was 

 demonstrated the correctness of the views held by the founder of modern chem- 

 istry, Lavoisier, as to the possibility of reducing air to the state of liquidity, by 

 producing liquids endowed with new and unknown properties." 



1 Comptes Rendus de VAcademie dcs Sciences, December 24, 1877. 



