1904.] 



on Liquid Hydrogen Calorimetry. 



583 



liydrogen, which at the temperature of 

 boiling nitrogen is still a permanent gas, 

 we 'should reach a temperature of — 214^ ; 

 and as this value would be just about the 

 melting point, the nitrogen ought con- 

 sequently to become solid. 



The freezing of nitrogen by evapora- 

 tion in a current of hydrogen at atmo- 

 spheric pressure is carried out in the fol- 

 lowing way. Within a vacuum vessel A A, 

 kept full of liquid air (Fig. 1), is inserted 

 another vacuum vessel B B, which is held 

 in its position by means of a cork C. About 

 the middle of B B is fixed another cork D, 

 which gives support to a tube E, allowing 

 free passage between the lower part of B B 

 and the atmosphere. F F F is a small tube 

 coiled round the tube E as far down as the 

 ■cork D, and below that continued as a coil 

 in the lower part of B B, and ending in a 

 nozzle at G. In the bottom of B B is placed 

 a quantity of liquid nitrogen N. The ex- 

 periment is conducted by passing pure 

 hydrogen through the tube F, thereby cool- 

 ing it to the boiling point of liquid air, and, 

 finally, by means of the nozzle CI through 

 the liquid nitrogen. As the hydrogen 

 passes down the spiral part of the tube F it 

 is cooled to the temperature of the gaseous 

 nitrogen rising from X, and bubbles 

 through N at the temperature of the 

 liquid nitrogen. These hydrogen bubbles 

 are thus in the best condition, according 

 to Dalton's law, to induce evaporation of 

 the liquid nitrogen, without conveying 

 unnecessary heat, and rapidly cause its 

 temperature to fall. After a short time 

 the hydrogen bubbles begin to move slug- 

 gishly in the cooling liquid nitrogen, and 

 soon afterwards the nitrogen becomes 

 solidified by its own evaporation. The 

 appearance of the solid nitrogen as it is 

 first formed is very extraordinary, as it 

 deposits in long spiral tubes through 

 which the hydrogen for a time escapes. 

 As we now know that helium is as much 

 more volatile a gas than hydrogen as the 



Fig. 1. 



\\^ 



