On the Laws of Electrolysis of Alkali Salt-Vapours. 207 



in and out, it was quite distinctly seen when it flashed in, and 

 its flashing out was equally distinct. 



It has been suggested to me by Professor Schuster that 

 the experiments seem to show that the red and violet carbon 

 lines must belong to different spectra of carbon, the particular 

 molecular combination which gives rise to the red line being- 

 destroyed by the presence of hydrogen. The fact that the 

 two interfering lines lie near each other in the spectrum is 

 probably accidental. I have to thank Professor Schuster 

 also for many other suggestions made during the course of 

 the experiments. 



XXI. The Laws of Electrolysis of Alkali Salt- Vapours. By 

 Harold A. Wilson, JD.Sc, M.Sc, B.A., Clerk-Maxwell 

 Student, Fellow of Trinity College, Cambridge*. 



IN 1891 Arrhenius (Wied. Ann. xlii. p. 18, 1891) pub- 

 lished the results of an investigation on the passage of 

 electricity through flames containing salt- vapours, and pro- 

 posed the theory that the salts dissociate into ions in the 

 flame in the same way that salts are ionized in aqueous 

 solutions. 



Arrhenius' results were confirmed and extended in 1899 

 in a research initiated by Prof. A. Smithells and carried out 

 in conjunction with Dr. H. M. Dawson and the writer (Phil. 

 Trans. A. 1899). Since then the writer has published 

 (Phil. Trans. A. 1899 and 1901) the results of further work 

 which seem to show conclusively that conduction through 

 salt-vapours is accomplished by means of ions of some kind, 

 and is therefore to this extent at least analogous to con- 

 duction through solutions. 



The experiments now to be described were undertaken 

 with the object of determining the relative conductivities of 

 different alkali salt-vapours at various temperatures. Many 

 of the results obtained have been published in a paper 

 on the " Electrical Conductivity of Air and of Salt- Vapours/'' 

 read to the Royal Society this year. 



In aqueous solutions a salt such as KC1 dissociates into 

 two ions +K and —CI, so that the most likely supposition 

 is that in salt-vapours the ions are of the same nature. 



However, determinations of the velocities of the various 

 ions in salt-vapours show 7 that the ions generally behave as 

 if they were much heavier than single atoms, and that the 

 positive ion always moves more slowly than the negative ion. 



* Communicated by the Author. (A paper read to the British 



Association, Glasgow, 1901.) 



