( 170 ) 



a. It is very instructive to see what happens when we proceed 

 to remove this cap and the glass is tilted over a little. Above the 

 level of the liquid hydrogen thick snowy clouds of solid air are 

 formed, the minute solid particles drop on the bottom through the 

 extremely light hydrogen (specific weight ViJ, there they collect to a 

 white pulver which, when the hj'drogen is shaken, behaves as heavy 

 sand would behave in water. When the hydrogen is evaporated that 

 sand soon melts down to liquid air ^). 



d. Solid hydrogen may be easily demonstrated when we place 

 the glass, fig. 3a, under a bell as fig. 3c in which a wire can 

 be moved up and down (for instance by fastening it into an india 

 rubber tube) and connect the bell with the airjiump. A starch-like 

 white cake is soon formed, which can be moved np and down 

 with the wire. 



e. To fill a vacuum flask as shown on PI. Ill we first cool it 

 by washing it out with liquid air. The connection at jV„, PI. I fig. 2 

 and PL III, is brought about simply by drawing a piece of india 

 rubber tubing N^^ over the new-silver tubes N^ and Co fitting into 

 each other, round which tlannel is swaddled. This again is enveloped 

 in loose wool. When some bottles are connected they are filled with 

 pure hydrogen through the tube h^ of Hydr. a after repeated 

 exhaustion and care is also taken that each newly connected bottle 

 is filled with pure hydrogen and that no air can enter the apparatus 

 while the connections are being made. 



When from the indications of the float L^^^ (PI. I, fig. 2) we 

 conclude that a bottle is full, it is disconnected, but as long as the 

 liquid hydrogen is kept in this glass the evaporating hydrogen is 

 allowed to escape into the gasholder, as is represented by PI. Ill for 

 Hydr. c. The disconnection at N\, is simply effected by taking off 

 the flannel band C^, heating the piece of india rubber tubing N^^ 

 (unvolcanized) with one's fingers (or with a pair of pinchers arranged 

 to this end) till it becomes soft again and can be shoved from the 

 tube N,. 



§ 7. 7\ansport to the cryostat, closure of the cycle. 

 a. The vacnum glasses filled with liquid hydrogen (see Hydr. d 

 on PL II) are transported to the room where the cryostat ^r is mounted 



1) All this has been demonstrated by me at the meeting of 28 May. To show 

 the small specific weight of hydrogen I held a very thin-walled glass bulb, which 

 sinks only a little in ether (as a massive glass ball in mercury), suspended by a 

 thin thread in the glass with liquid hydrogen, where it fell like a massive glass 

 ball in water and tapped on tlae bottom. 



