146 NEW EESEAKCHES ON LIQUID AIR. 



ature. In order to raise the critical point of hydrogen to about — 200°, 

 from 2 to 5 per cent of nitrogen or air was mixed with it. This is sim- 

 ply making an artificial gas containing a large proportion of hydrogen, 

 which is capable of liquefaction by the use of liquid air. The results 

 are summed 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, viz, that by subjecting it to a high com- 

 pression at a temperature of — 200°, and. expanding the resulting liquid 

 iuto air, a much lower temperature than anything tbat has been recorded 

 up to the present time can be reached. This is proved by the fact that 

 such a mixed gas gives, under the conditions, a paste or jelly of solid 

 nitrogen, evidently giving off hydrogen because the gas coming off 

 burns fiercely. 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 has been successful. 1 



In Professor Olszewski's x^aper " On the liquefaction of gas," 2 after 

 detailing the results of his hydrogen experiments, he says : " The reason 

 for which it has not hitherto been possible to liquefy hydrogen in a 

 static state is, that there exists no gas having a density between 

 that of hydrogen and nitrogen, and which might be, for instance, 

 7 — 10 (H = l). Such a gas would be liquefied by means of liquid 

 oxygen or air as cooling agent, and afterwards used as a recognized 

 menstruum in the liquefaction of hydrogen. Science will probably 

 have to wait a very long time before this suggestion of how to get 

 "static" liquid hydrogen is realized. The proposal Wroblewski made 

 in 1884, of using the expansion of hydrogen as a cooling agent to effect 

 the change of state, is far more direct and practicable. 



Liquid hydrogen jet and solid hydrogen. — Hydrogen cooled to — 194° 

 (80° abst. /.), the boiling point of air, is still at a temperature which is 

 two and a half times its critical temperature, and its direct liquefaction 

 at this point would be comparable to that of air taken at 60°, and 

 liquefied by the apparatus just described. In other words, it is more 

 difficult to liquefy hydrogen (assuming it to be supplied at the tem- 

 perature of boiling air) than it is to produce liquid air starting from 

 the ordinary atmospheric conditions. Now, air supplied at such a 

 high temperature greatly increases the difficulty and the time required 

 for liquefaction. Still it can be done, even with the air supply at 100°, 

 in the course of seven minutes, and this is the best proof that hydrogen, 

 if placed under really analogous conditions, namely, at — 194°, must 

 also liquefy with the same form of apparatus. It is almost needless 

 to say that hydrogen under high compression at the temperature of 

 15° C. passed through such a regenerating coil, produced no lowering 

 of temperature. Hydrogen cooled to — 200° was forced through a fine 



1 The compressed gas mixture at above — 210° was expanded into a large cooled 

 vacuum vessel. 

 - Phil. Mag., 1895. 



