LIQUEFACTION OF HYDROGEN AND HELIUM. 263 



the nozzle of a coil of pipe at the rate of about 10 or 15 cubic feet per 

 minute, in a vacuum vessel doubly silvered and of special construc- 

 tion, all surrounded with a space kept below —200°, liquid hydrogen 

 commenced to drop from this vacuum vessel into another doubly 

 isolated by being surrounded by a third vacuum vessel. In about live 

 minutes 20 cubic centimeters of liquid hydrogen were collected, when 

 the hydrogen jet froze up, from the accumulation of air in the pipes 

 frozen out from the impure hydrogen. The yield of liquid was about 1 

 per cent of the gas. The hydrogen in the liquid condition is clear and 

 colorless, showing no absorption spectrum, and the meniscus is as well 

 defined as in the case of liquid air. The liquid must have a relatively 

 high refractive index and dispersion, and the density appears also to 

 be in excess of the theoretical density, namely, 0.18 to 0.12, which we 

 deduce respectively from the atomic volume of organic compounds, and 

 the limiting density found by Amagat for hydrogen gas under infinite 

 compression. Yet this may be a delusion due to its high dispersion. 

 A preliminary attempt to weigh a small glass bulb in the liquid made 

 the density about 0.08. My old experiments on the density of hydrogen 

 in palladium gave a value for the combined element of 0.62, and it will 

 be interesting to find the accurate density of the liquid substance at 

 its boiling point. Not having arrangements at hand to determine the 

 boiling point, other than a therino-junction which gave entirely falla- 

 cious results, experiments were made to prove the excessively low 

 temperature of the boiling fluid. In the first place, if a long piece of 

 glass tubing, sealed at one end and open to the air at the other, is 

 cooled by immersing the closed end in the liquid hydrogen, the tnbe 

 immediately fills, where it is cooled, with solid air; a small tube con- 

 taining liquid oxygen became a bluish solid. A first trial of putting 

 the liquid hydrogen under exhaustion gave no appearance of transi- 

 tion into the solid state. The liquid hydrogen in its vacuum tube, which 

 is immersed in liquid air so that the external wall of the vacuum vessel 

 is maintained at about — 190°, is found to evaporate at a rate not far 

 removed from that of liquid air from a similar vacuum vessel under the 

 ordinary conditions of storage. This leads me to the conclusion that 

 with proper isolation it will be possible to manipulate with liquid hydro- 

 gen as easily as with liquid air. The second experiment was made 

 with a tube containing helium. 



The Cracow Academy Bulletin for 1896 contains a paper by Professor 

 Olszewski, entitled "A research on the liquefaction of helium," in which 

 he states, "As far as my experiments go, helium remains a permanent gas 

 and apparently is much more difficult to liquefy than hydrogen." In a 

 paper of my own in the proceedings of the Chemical Society, No. 183 

 (1896-97), in which the separation of helium from Bath gas was effected 

 by a liquefaction method, the suggestion was made that the volatility 

 of hydrogen and helium would probably be found close together, just 

 like tbose of fluorine and oxygen. Having a specimen of purified 



