[MCLENNAN & shrum] LIQUEFACTION OF HYDROGEN 



181 



Shakspear katharometers have been found to be almost indis- 

 pensable for testing the hydrogen during the operation of the cycle, 

 and while using them they are frequently calibrated and checked by 

 means of hydrogen that has been chemically analysed, or tested by 

 other physical means. 



It is well known, however, that any trace of impurity in the 

 hydrogen- — -other than helium — will be condensed and later solidified 

 in the expansion coil of the hydrogen liquéfier. Such condensation 

 and solidification finally results in a complete stoppage of the ex- 

 pansion valve or of the tubes of the expansion coil. It is only possible, 

 therefore, with other than absolutely pure hydrogen to make a 

 limited amount of liquid hydrogen during each operation. In order 

 to make 30 or 40 litres of liquid hydrogen without failure it is necessary 

 to have available a large supply of extremely pure hydrogen. This 

 is accomplished by an arrangement similar to that employed by 

 Professor Kammerlingh Onnes in the Cryogenic Laboratory at 

 Leiden.'^ It consists of an apparatus in which the gaseous impurities 

 in impure hydrogen are condensed out by means of liquid hydrogen. 

 Fig. 3 represents the apparatus schematically. 



TÛ MCi/OM Pi^P 



F^JHiri£0 HYDROGSN 





iàgt 



HVORCfOCN IHLCT 



cusr/LLCO HYDfxxcn rg caso.'ii Tim 



'.'•'irj'' 



S! 



HYDROGEN 

 PURiriCR 



Fig. 3 



'Kon. Akad. Weten, Amsterdam, 11, 1908-09. 



