254 



SOLID HYDROGEN. 



the influx of heat l\y being- placed in a vacuum vessel, and the conden- 

 sation of its vapor must be eflfected by the use of liquid hydrogen. 



No boiling-out operation is necessary with the cryophorous we are 

 about to use. The apparatus is shown in fig. 6. The vacuum tube B 

 contains liquid nitrogen. It is titted on by an india rubber joint to 

 a wide piece of glass tubing doubly bent at right angles, A D; and 

 in order to allow the gas from the boiling liquid to escape before the 



TO EXHAUST 



experiment begins, an aperture, C, is left which can be closed with 

 a stopcock. On closing C and inserting a part of the tube A into a 

 vessel containing" liquid hydrogen, the gas within is condensed, and 

 thereby the pressure of the vapor in the interior of the vessel is 

 reduced, forcing the liquid nitrogen in the other part of the apparatus 

 to boil with great violence. In a few minutes the temperature of the 

 nitrogen is so much reduced that it passes into the solid state. Many 



