Intelligence and Miscellaneous Articles. 159 



liquefaction and solidification of hydrogen. I made use of exactly 

 the same apparatus as for the liquefaction of oxygen, employing 

 protoxide of nitrogen instead of carbonic acid. 

 ' To obtain the hydrogen under pressure, I employed the decom- 

 position of formiate of potass by caustic potass. The hydrogen 

 was liberated without any trace of water, and the residue is not 

 volatile — two conditions essential for the rigorous accuracy of the 

 observations. The temperature of the reaction is well defined, and 

 did not rise. The liberation of hydrogen proceeded with perfect 

 regularity. The pressure reached 650 atmospheres before becoming 

 stationary. The hydrogen disengaged corresponded to 252 litres 

 at zero. The cold was about — 140° (I have not yet effected the 

 reduction of the measurement of the temperature). When I opened 

 the stopcock, liquid hydrogen issued with vehemence from the 

 orifice, producing a sharp hissing sound. The jet had a steel-blue 

 colour, and was perfectly opaque for a length of about 12 centi- 

 metres. At the same time a rattling was heard upon the floor like 

 the noise made by hail falling upon the ground, and the hissing was 

 changed into a whistling which resembled that heard when a piece 

 of sodium is thrown upon water. Almost immediately, the jet 

 became intermittent, and shocks were felt in the cock at each issue. 



During the first stream the pressure fell from 650 atmospheres 

 to 370. After closing the cock the pressure diminished gradually 

 during several minutes down to 215 atmospheres ; it then rose 

 again slowly up to 225, at which it again became stationary. I re- 

 opened the cock ; but the jet issued in such an intermittent manner 

 that it was evident hydrogen had congealed in the tube. This hy- 

 pothesis was demonstrated by the progressive exit of all the hydro- 

 gen when I had stopped the pumps and the production of cold. I 

 explain the difference between these results and those which I 

 obtained for oxygen as follows : — 



The atomic weight of hydrogen is -J-- 6 of that of oxygen ; therefore 

 the latent heat of liquid hydrogen must be certainly ten times that 

 of oxygen. As soon as the exit-cock is opened a portion of the 

 liquid stored in the tube evaporates, absorbing such an amount of 

 heat by this change of state that the rest solidifies in the tube, even 

 before it can be driven out. 



During more than a quarter of an hour we had successive dis- 

 charges of hydrogen through the orifice. The fog produced by the 

 sudden expansion of the gas at the commencement of the experiment 

 descended as far as the ground ; but it ceased completely as soon as 

 the jet became intermittent, which corresponded to the congelation 

 of hydrogen in the interior of the tube. It is impossible to con- 

 found the vesicular fog of the gas with the appearance of the liquid 

 jet at the outset. These different appearances are perfectly dis- 

 tinct and give rise to no ambiguity. 



I know the volume of the residue, which is only carbonate of 

 potass ; and I shall be able in the next experiment to determine 

 the density of liquid hydrogen. — Comjptes Rendus de VAcademie des 

 Sciences, Jan. 14, 1878, tome lxxxvi. pp. 106, 107. 



