LIQUID HYDROGEN. 135 



and research at low temperatures,"' ' in which occasion was taken to 

 describe for the tirst time the mode of production and use of a liquid 

 hydrogen jet. * ■^' * 



The report of a Friday evening discourse on ' ' New researches on 

 liquid air"'^ contains a drawing of the apparatus employed for the 

 production of a jet of hydrogen containing visible liquid. This is 

 reproduced in tig. 1. A represents one of the hydrogen cjdinders; B 

 and C, vacuum vessels containing carbonic acid under exhaustion and 

 liquid air, respectively; I) is the coil; G, the pin-hole nozzle, and F, the 

 valve. By means of this hydrogen jet liquid air can ])e quickly trans- 

 formed into a hard solid. It was shown that such a jet could be used 

 to cool l)odies ))elow the temperature that it is possible to reach by the 

 use of liquid air, but all attempts to collect the liquid hydrogen from 

 the jet in vacuum vessels' failed. No other investigator improved on 

 my results,^ or has indeed touched the subject during the last three 

 3^ears. 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. This apparatus took a year to build, and many months 

 have been occupied in the testing and preliminary trials. Th(^ man}^ 

 failures and defeats need not be detailed. 



On May 10, 1898, starting with hydrogen 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 1.5 cubic feet per 

 miiuite, in a vacuum vessel doul)ly silvered and of special construction, 

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

 menced to drop from this vacuum vessel into another dou])ly isolated 

 by being surrounded with a third vacuum vessel. In about live minutes 

 20 cubic centimeters of liquid hydrogen were collected, when the hydro 

 gen jet froze up, from the accumulation of air in the pipes frozen out 

 from the impure hydrogen. The jdeld of liquid was about 1 per cent 

 of the gas. The hydrogen in the liquid condition is clear and color- 

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

 defined as in the case of liquid air. The liquid must have a relativ^ely 

 high refracti^'e index and dispersion, and the density appears at first 

 sight to ])e in excess of the theoretical density, namely, 0.18 to 0.12, 

 which we deduce respectively from the atomic volume of organic com 

 pounds and the limiting density found hy 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 theoretical. My old experiments on the density of hydrogen 

 in palladium gave a value for the coml)ined element of 0.62. Not 

 having arrangements at hand to determine the boiling point other than 



' Proceedings of the Chemical Society, No. 158, 1895. 

 ^ Proceedings of the Roval Institution, 1896. 



