134 LIQUID HYDROGEN. 



The accuracy of Wroblewski's deductions regarding the chief con- 

 stants of liquid hydrogen, following from a study of the isothcn-nials 

 of the gas, is a signal triumph for the theory' of Van der Waals and a 

 monument to the genius of the Krakow physicist. From the results 

 we may safely infer that, supposing a gas is hereafter discovered in 

 small quantity four times more volatile than liquid hydrogen, having 

 a boiling point of about 5° absolute, and therefore incapable of direct 

 liquefaction by the use of liquid hydrogen, yet by a study of its iso- 

 thermals we shall succeed in finding out its most important liquid con- 

 stants, although the isolation of the real liquid may for the time be 

 impossible. 



In a paper pul>lished in the Philosophical Magazine, Septeml)er, 

 1884, "On the licjucfaction of ox3'gen and the critical volumes of 

 fluids," the suggestion was made that the critical pressure of hydro- 

 gen was wrong, and that instead of being !>'.) atmospheres (as d(>duced 

 by Sarrau from Aniaj^at's isothernials) the gas had prol)ably an abnor- 

 mally low value for this constant. This view was substantially con 

 firmed by Wroblewski finding the critical pressure of 18.3 atmos- 

 pheres, or about one-fourth of that of oxygen. The Chemical News, 

 September 7, 1894, contains an account of the stage the author's 

 hydi'ogen experiment had rcniched at that date. The object was to 

 collect liquid hydrogen at its hoiling point, in an open vacuum vessel, 

 which is a much more difficult problem than seeing it in a glass tube 

 under pressure and at a higher temperature. In order to raise the 

 critical point of hydrogen to al)out — 210 . fi'om 'I to 5 per cent of 

 nitrogen or air was mixed with it. This is simph' making an artificial 

 gas containing a large proportion of hydrogen which is capable of 

 liquefaction b}' the use of li({uid air. The results are sununed up in 

 the following extract from the paper: 



"One thing can, however, be proved by the use of the gaseous 

 mixture of hydrogen and nitrogen, namely, that b}- subjecting it to a 

 high compression at a temperature of —200'-' and expanding the result- 

 ing li([uid into air. a much lower temperature than anything that has 

 been recorded up to the present time can be reached. This is proved 

 by the fact that such a mixed o-as gives, under the conditions, a paste 

 or jelly of solid nitrogen, evidently giving off hydrogen, because the 

 gas coming ofi' burns tierceh\ Even when hydrogen containing only 

 some 2 to 5 per cent of air is similarly treated, the result is a white 

 solid matter (solid air) along with a clear liquid of low density, which 

 is so exceedingly volatile that no known device for collecting it has 

 been successful."" 



This was in all probability the first liquid hydrogen obtained, and 

 the method is applicable to other difficultly liquefactible gases. 



Continuing the investigations during the winter of 1894 and the 

 greater part of 1895, the author read a paper before the Chemical 

 Society in December of that year entitled "The liquefaction of air 



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