646 



SCIENCE. 



[N. S. Vol. XI. No. 278- 



drogen. This apparatus took a year to 

 build, and many months have been occu- 

 pied in the testing and preliminary trials. 

 The many failures and defects need not be 

 detailed. 



On May 10, 1898, starting with hydro- 

 gen cooled to — 205°, and under a pressure 

 of 180 atmospheres, escaping continuously 

 from the nozzle of a coil of pipe at the rate 

 of about 10 to 15 cubic feet per minute, in 

 a vacuum vessel doubly silvered and of 

 special construction, all surrounded with a 

 space kept below —200°, liquid hydrogen 

 commenced to drop from this vacuum vessel 

 into another doubly isolated by being sur- 

 rounded with a third vacuum vessel. In 

 about five minutes, 20 c.c. of liquid hy- 

 drogen were collected, when the hydrogen 

 jet froze up, from the accumulation of air 

 in the pipes frozen out from the impure hy- 

 drogen. The yield of liquid was about one 

 per cent, of the gas. The hydrogen in the 

 liquid condition is clear and colorless, show- 

 ing no absorption spectrum, and the menis- 

 cus 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 at first sight 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. 

 A preliminary attempt, however, to weigh 

 a small glass bulb in the liquid made the 

 density only about 0.08, or half the theo- 

 retical. My old experiments on the density 

 of hydrogen in palladium gave a value for 

 the combined element of 0.62. ISTot having 

 arrangements at hand to determine the boil- 

 ing point other than a thermo-j unction 

 which gave entirely fallacious results, ex- 

 periments were made to prove the exces- 

 sively low temperature of the boiling fiuid. 

 In the fii'st 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 tube 

 immediately fills where it is cooled with 

 solid air. A small glass tube filled with 

 liquid oxygen when cooled in liquid hy- 

 drogen is transformed into a bluish white 

 solid. This is a proof that the boiling point 

 of hydrogen is much lower than any tem- 

 perature previously reached by the use of 

 liquid nitrogen evaporating in vacuo, seeing 

 oxygen always remains liquid under such 

 conditions. A first trial of putting liquid 

 hydrogen under exhaustion gave no ap- 

 pearance of transition into the solid state. 

 When the vacuum tube containing liquid 

 hydrogen is immersed in liquid air so that 

 the external wall of the vacuum vessel is 

 maintained at about — 190°, the hydrogen 

 is found to evaporate at a rate not far re- 

 moved from that of liquid air from a sim- 

 ilar vacuum vessel under the ordinary con- 

 ditions of temperature. This leads me to 

 the conclusion that, with proper isolation, 

 it will be possible to manipulate liquid hy- 

 drogen as easily as liquid air. 



The boilng poiut of liquid hydrogen at 

 atmospheric pressure in the first instance 

 was determined hy d„ platinum- resistance ther- 

 mometer. This was constructed of pure metal 

 and had a resistance of 5.3 ohms at 0° C, 

 which fell to about 0.1 ohm when the ther- 

 mometer was immersed in liquid hydrogen. 

 The reduction of this resistance to normal 

 air thermometer degrees gave the boiling 

 points —238.2° and —238.9° respectively by 

 two extrapolation methods, and — 237° by a 

 Dickson formula.* The boiling point of the 

 liquid seems therefore to be —238° C. or 35° 

 absolute, and is thus about 5° higher than that 

 obtained by Olszewski by the adiabatic ex- 

 pansion of the compressed gas, and about 8° 

 higher than that deduced by Wroblewski 

 from Van der Waal's equation. From these 

 results it may be inferred that the critical 

 point of hydrogen is about 50° absolute, 

 *See Phil. Mag., 45, 525, 1898. 



