Page:Popular Science Monthly Volume 12.djvu/638

620 same phenomenon is observed in releasing carbonic acid, and protoxide and bioxide of nitrogen, which have been subjected to strong pressure."

After having obtained these results, at a session of the Academy on December 31st, M. Cailletet announced that he had won a complete victory 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 Rendus 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 vertical 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 temperature 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 peculiar; 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 repeating my experiments to-day, December 31st, in the presence and with the assistance 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 atmospheric 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 chemistry, Lavoisier, as to the possibility of reducing air to the state of liquidity, by producing liquids endowed with new and unknown properties."