256 Prof. J. Dewar. 



" Preliminary Note on the Liquefaction of Hydrogen and 

 Helium." By JAMES DEWAR, M.A., LL.D., F.R.S., Ful- 

 lerian Professor of Chemistry in the Royal Institution. 

 Received and read May 12, 1898. 



In a paper entitled " The Liquefaction of Air and Research at 

 Low Temperatures," read before the Chemical Society, and pub- 

 lished in their 'Proceedings,' No. 158, an account is given of the 

 history of the hydrogen problem and the result of my own experi- 

 ments up to the end of the year 1895. The subject is again dis- 

 cussed in a Friday Evening Lecture on " New Researches on 

 Liquid Air,"* which contains a drawing of the apparatus employed 

 for the production of a jet of hydrogen containing liquid. It was 

 shown that such a jet could be used to cool bodies below the tem- 

 perature that could be reached by the use of liquid air, but all 

 attempts to collect the liquid in vacuum vessels failed. No other 

 investigator has so far improved on the results described 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 circuits and arrangements for the liquefaction of 

 hydrogen, which will be described in a subsequent paper. This 

 apparatus, admirably constructed by the engineers, Messrs. Lennox, 

 Reynolds, and Fyfe, took a year to build up, and many months have 

 been occupied in testing and making preliminary trials. The many 

 failures and defeats need not be detailed. 



On May 10, 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 doubly isolated by being surrounded with a third vacuum 

 vessel. In about five minutes, 20 c.c. of liquid hydrogen were col- 

 lected, when the hydrogen 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 colourless, show- 

 ing 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 theoretical density, viz., 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 



* ' Roy. Inst. Proc.,' 1896. 



