338 Professor Liming, On Differences 



On Differences between the Spectra at Anode and Kathode in 

 certain gases, and on the probable reasons for these differences. 

 By G. D. Liveing, M.A., Professor of* Chemistry. 



[Bead 18 January 1904.] 



It is well known that the spectrum of the glow about the 

 kathode, when a continuous electric discharge passes through 

 rarefied gas, is, in some cases, different from that of the light 

 emitted by the gas in other parts of the tube. 



In the case of nitrogen both these spectra were carefully 

 described by Angstrom and Thalen in 1875 1 , and were dis- 

 tinguished by them from the, so-called, line spectrum, which 

 is produced in nitrogen by a disruptive discharge. They noticed 

 that the glow about the kathode increased, and became more 

 brilliant, as the gas was more rarefied, but they attributed the 

 light at the anode to an oxide of nitrogen. Another element 

 well known to give two spectra in the same tube at reduced 

 pressure is hydrogen 2 , but I am not aware that anyone hitherto 

 has pointed out that these two spectra bear to each other a 

 relation similar to that which subsists between the two chan- 

 nelled spectra of nitrogen, namely, that one, the series of rays 

 corresponding to the Fraunhofer lines 0, F, G', h and Huggins' 

 ultra-violet series, is that of the kathode glow, while the second 

 spectrum, also consisting of lines, but much more numerous, is 

 that of the anode. It is as easy to shew this as to shew the 

 corresponding facts with regard to the spectra of nitrogen. To 

 shew it clearly it is necessary to have the hydrogen as pure as 

 possible. I have used hydrogen occluded in palladium which was 

 enclosed in a glass tube fitted with a stopcock, which may be called 

 stopcock (a). This tube, beyond (a), was sealed by fusion to a 

 long and wide tube loosely filled with phosphoric anhydride, also 

 having a stopcock (b) at its farther end, beyond which it was 

 sealed to the sparking tube, and this in. turn to a mercury pump. 

 Stopcock (b) being open and (a) shut, the air in the system was 

 exhausted as completely as the pump would do it. Stopcock (6) 

 was then closed and (a) opened to allow hydrogen from the 

 palladium to fill the tube holding phosphoric anhydride, and then 

 (a) was closed again. The whole was left in this state all night. 

 Next morning on passing a spark the tube shewed the well known 



1 " Recherches sur les spectres des metalloids," Nova Acta Reg. Soc. Sc. Ups., 

 Ser. in. 



- Pliicker and Hittorf, 'Trans. R. S., 1865. 



