at the Royal Institution, 1908-1916 



■65 



^ The work of Low-Temperature Research, however, like that of 

 Davy and Faraday, has brought repute to the Institution and its 

 author has had the great satisfaction of seeing it already bear fruit 

 in many practical directions— that others reap where he has sown. 

 The purpose of the Institution has thus been fulfilled ! 



Abasement of Temperature. 



SOLIDIFICATIOX OF HyDROGEN AXD OxYGEN. 



The solidification of hydrogen, on exhausting the gas by an air- 

 pump from above the liquid, was first demonstrated in the Institution 

 Theatre on April 6, 1900. Later it was shown that another method 

 is to bubble the more volatile helium through the liquid. Far the 

 most telling method, however, which is also a most effective demon- 

 stration of the extraordinary gaseous avidity of cooled charcoal, is 

 that given on June 5, 1908, with the apparatus figured in vol. xix, 

 p. 422, of the Proceedings of the Institution (Fig. 2). 



Owing to the small vapour pressure of oxygen at its melting 

 point, liquid oxygen cannot be solidified even with the aid of a 

 powerful pump of the ordinary kind. The production of sohd oxygen, 

 as a transparent jelly, was first demonstrated on January 20, 1911, 

 with the aid of charcoal cooled in Hquid oxygen ; the apparatus is 

 figured at p. 261 of the Institution Proceedings (1911, vol. xx. Fig. 3). 

 Subsequently, it was shown (Jan. 23, 1914) that liquid oxygen, cooled 

 only by liquid air, can be solidified directly by using the Gaede pump, 

 by means of which a very high degree of exhaustion may be effected 

 rapidly. As soon as the vacuum is no longer maintained, the jelly 

 melts. The very different pressures at which the various sohdified 

 gases melt are shown in the following table : — 



:2 The advantage of using liquid hydrogen in place of liquid air or 

 oxygen has been demonstrated in many ways in the course of Sir 



