THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



JANUARY 1893. 



I. The Electrical Properties of Pure Substances. — Part I. The 

 Preparation of Pure Nitrogen and attempts to Condense it. 

 By Professor R. Threlfall*. 



[Plate I.] 



IN 1886 a paper was published in the Proceedings of the 

 Royal Society by Professor J. J. Thomson and myself, 

 " On an Effect produced by the passage of an Electric Dis- 

 charge through Pure Nitrogen." The effect in question was 

 briefly as follows : — When a nitrogen tube provided with a 

 small mercury or sulphuric-acid gauge is exhausted to a pres- 

 sure of about 8 millim. of mercury and then sparked with a 

 discharge too small to heat the tube in a sensible manner, a 

 diminution of the elastic force of the enclosed gas is observed. 

 This diminution was found to be independent of the size or 

 material of the electrodes, of the volume of the tube or the 

 extent of its surface, but to depend on the kind of discharge 

 employed, and its duration ; on the temperature and pressure 

 of the gas in the tube during the process of sparking and 

 afterwards. Arguing by exclusion, we attributed the diminu- 

 tion of pressure to a condensation of nitrogen molecules, 

 similar to the condensation which oxygen undergoes when 

 converted into ozone. 



This property of nitrogen, if established, would be of un- 

 doubted interest, and consequently in 1889 I undertook a 



* Communicated by the Author. 

 Phil. Mag. S. 5. Vol. 35. No. 212. Jan. 1893. B 



