( H4) 



The electroljtic hydrogen prepared under excess of pressure in 

 the improved generating apparatus tlows off through a fine regidating 

 cock (see 11, PI. I, Comni. N". 27). It is, liowever, not directly 

 admitted into the mercury airpump and the measuring apparatus 

 which is to be filled, but is first led through a steel capillary to 

 the piezometer in a pressure cylinder where pressure is exerted by 

 compressed air, as was used in the experiments on the condensation of 

 gaseous mixtures (see Comm. N°. 92, Sept. '04, PI. I, fig. 1). The 

 stem of this piezometer carries a three way stopcock (Comm, N". 84, 

 March '03 PI. I figs. 2 and 3), to which are connected on the one 

 side the above mentioned capillary, on the other side a copper cooling 

 tube (a platinum cooling tube with platinum capillaries would still 

 have been better), which at either extremity ends in steel capillaries 

 with connections. A high pressure cock, which admits of a tine 

 regulation, connecls the cooling tube with the mercury air pump 

 and the measuring apparatus. All the packings are made of cork, 

 the gas itself has no contact with anything but the metal of the cooling 

 tube and the capillaries, with glass, or with twice distilled mercury. 

 After all parts between the generating apparatus and the mercury 

 airpump ha\e been carefully exhausted, the gas is admitted from 

 the generating apparatus into the piezometer with the cooling tube, 

 then the latter are shut off from the generating apparatus and the 

 mercury in the piezometer is forced up until a pressure of 60 atni. 

 is reached, the cooling tube being immersed in liquid air up to the 

 steel capillaries. At the same pressure the gas is then led through 

 the regulating cock into the measuring apparatus that are to be filled. 



§ 3. Hydrogen for the cycle ivith liquid hydrogen. The commercial 

 electrolytic hydi'Ogen is as a rule too much contaminated with oxygen 

 and air to serve for a circulation of hydrogen. In order to separate 

 these admixtures we may compress it in a cooling tube immersed 

 in oxygen, \vhich evaporates in vacuo. The following operation is 

 simpler still. The hydrogen is compressed and led through a cooling 

 tube immersed in liquid air under normal pressure into the appa- 

 ratus where liquid hydrogen is 'prepared by means of a regenerator 

 spiral, which apparatus together with a gasholder, the compressors and 

 drying apparatus forms a cycle. The pressure of compression is now 

 tegulated so that the compressed gas floAvs out without blocking the 

 delivery cock of the regenerator spiral, at least not as long as this 

 cock is opened and shut alternately. The pressure is gradually raised 

 higher and higher, while the temperature of the outflowing gas falls, 

 and this is continued until the cock is blocked, and the pause during 



