JDLT 1, 1898.] 



SCIENCE. 



occupy. The number 22.51 must be taken 

 as a minimum densitJ^ If we may hazard 

 a conjecture it is that krypton will turn 

 out to have the density 40, with a corre- 

 sponding atomic weight 80, and will be 

 found to belong to the helium series, as is, 

 indeed, rendered probable by its withstand- 

 ing the action of red-hot magnesium and 

 calcium on the one hand, and on the other 

 of oxygen in presence of caustic soda, under 

 the influence of electric sparks. We shall 

 procure a larger supply of the gas and en- 

 deavor to separate it more completely from 

 argon by fractional distillation. 



It may be remarked in passing that 

 Messrs. Kayser and Friedlander, who sup- 

 posed that they had observed D, in the 

 argon of the atmosphere, have probably 

 been misled by the close proximity of the 

 brilliant yellow line of krypton to the 

 helium line. 



On the assumption of the truth of Dr. 

 Johnstone Stoney's hypothesis that gases of 

 a higher density than ammonia will be 

 found in our atmosphere, it is by no means 

 improbable that a gas lighter than nitrogen 

 will also be found in air. We have already 

 spent several months in preparation for a 

 search for it, and will be able to state ere 

 long whether the supposition is well 

 founded. 



LIQUID HYDROGEN. 



PRELIMINARY NOTE ON THE LIQUEFACTION 



OF HYDROGEN AND HELIUM.* 



In a paper entitled ' The Liquefaction of 

 Air and Research at Low temperatures," 

 read before the Chemical Society, and pub- 

 lished in their ' Proceedings,' ISTo. 158, an 

 account is given of the history of the hydro- 

 gen problem and the result of my own ex- 

 periments up to the end of the year 1895. 

 The subject is again discussed in a Friday 

 Evening Lecture on ' liew Researches on 



*Eead before the Eoyal Society, London, May 12, 

 1898. 



Liquid Air,'* which contains a drawing of 

 the apparatus employed for the production 

 of a jet of hydrogen coataiuing liquid. It 

 was shown that such a jet could be used to 

 cool bodies below the temperature that 

 could be reached by the use of liquid air, 

 but all attempts to .collect the liquid in 

 vacuum vessels failed. No other investi- 

 gator has so far improved on the results de- 

 scribed in 1895. The type of apparatus 

 used in these experiments worked well, so 

 it was resolved to construct a much larger 

 liquid air plant, and to combine with it cir- 

 cuits and arrangements for the liquefaction 

 of hydrogen, which will be described in a 

 subsequent paper. This apparatus, admi- 

 rably constructed by the engineers, Messrs. 

 Lennox, Reynolds, and Fyfe, took a year to 

 build up, and many months have been oc- 

 cupied in testing and making preliminary 

 trials. The many failures and defeats need 

 not be detailed. 



On May 10th, starting with hydrogen 

 cooled to — 205° C, and under a pressure 

 of 180 atmospheres, escaping continuously 

 from the nozzle of a coil of pipe at the rate 

 of about 10 cubic feet to 15 cubic feet per 

 minute, in a vacuum vessel double-silvered 

 and of special construction, all surrounded 

 with a space kept below — 200° C, liquid 

 hydrogen commenced to drop from this 

 vacuum vessel into another doublj' isolated 

 by being surrounded with a third vacuum 

 vessel. In about five minutes, 20 cc. of 

 liquid hydrogen were collected, when the 

 hj'drogen jet froze up from the solidification 

 of air in the pipes. 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 has a relatively high 

 refractive index and dispersion, and the 

 density appears to be in excess of the theo- 

 retical density, viz., 0.18 to 0.12, which we 



*'Eoy. Inst. Proo.,' 1886. 



