1 8 ATTAINMENT OF VERY LOW TEMPERATURES. 



The hydrogen which hquefied in H was drawn off and collected by 

 the method described on page 20. The arrangements for the com- 

 pression and circulation of the hydrogen gas will also be dealt with 

 later. 



The modifications which were introduced into the apparatus, when 

 I recommenced my experiments in 1902, were simple though important. 

 As originally constructed the coil in the liquid air chamber B was so 

 short that it did not present sufficient surface for the effective cooling 

 of the compressed gas passing through it. Further, the chamber B 

 was so narrow that not only was it difficult to fill it with liquid air, but 

 if, through irregular adjustment of the valve, there was a sudden rush 

 of gas through the coil, the liquid air boiled violently, and overflowed 

 the chamber. 



This difficulty was easily overcome by introducing between A and B 

 (fig. 3, B) a coil B' consisting of two five-meter lengths of copper pipe 

 wound into an open spiral. The pipes were carefully spaced by means 

 of pieces of copper wire soldered to them at intervals. The coil was 

 immersed in liquid air contained in the inner of two glass beakers, 

 which were separated by pieces of cork, so as to leave an air space 

 between them, and surrounded with a thick layer of natural wool. 



A copper funnel was also soldered to the top of the tube which 

 formed the chamber B, to facilitate the operation of filling it with liquid 

 air. The apparatus as thus modified was used about ten times. Of 

 these experiments only one failed through a break-down in the com- 

 pressor. 



VIII. The Second Hydrogen Liquefier. 



Shortly after I had completed the researches I have just referred to, 

 I was asked by Professor d'Arsonval of Paris, and by Professor 

 Anschiitz of Bonn, to design hydrogen liquefiers for their laboratories. 

 As I had not then carried out any further experiments with a view to 

 improving my method of liquefying hydrogen, and as the apparatus 

 I had already constructed had given me perfect satisfaction, except that 

 it was not very economic so far as the refrigerants, liquid air and car- 

 bon dioxide, were concerned, I designed another machine of the same 

 principle but of a more compact form. The apparatus was constructed 

 by Brin's Oxygen Company. 



A section of the apparatus is shown in fig. 4. The hydrogen from 

 the compressor enters the apparatus at the cross-piece below the pres- 

 sure gauge and passes first through the coil in the chamber A, which is 

 intended to contain a mixture of carbonic acid and alcohol. The whole 

 system of coils is double, each component being of the same length. 

 The total length of copper coil in each of the chambers A and B is 

 about twenty meters. The cock x is intended to allow the hydrogen 



