144 Professor Deivar [March 27, 



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 compression at a temperature of — 200°, and expanding 

 the resulting liquid into air, a much lower temperature than any- 

 thing that 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." * 



In Professor Olszewski's paper " On the Liquefaction of Gas," f 

 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 = 1). Such a gas would be liquefied by means 

 of liquid oxygen or air as cooling agent, and afterwards used as a 

 recognised menstruum in the liquefaction of hydrogen. Science 

 will probably have to wait a very long time before this sug- 

 gestion of how to get " static " liquid hydrogen is realised. The 

 proposal Wroblewski made in 1884 of using the expansion of hydro- 

 gen 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. t.), 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 temperature of boiling air) than it is to produce liquid air start- 

 ing 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 nozzle under 140 atmos. pressure, and yet 



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

 cooled vacuum vessel. 

 t Phil. Mag. 1895. 



