214 The Laivs of Electrolysis of Alkali Salt- Vapours, 



alkali salts in the state of vapour. This must be regarded as 

 very conclusive evidence in favour of the theory that the 

 passage of electricity through salt-vapours is a process very 

 analogous to the electrolysis of salt-solutions. 



In a dilute solution of such a salt as KC1 each molecule of 

 the salt is believed to dissociate into two ions + K and —CI. 

 According to the corpuscular theory of electricity, if we 

 denote a corpuscle by a, then these ions are K— a. and Cl + a. 



The results described in this paper prove that the amount 

 of electricity which can be transported by salt in the form of 

 vapour i ? equal to the amount required to electrolyse the 

 same amount of salt in a solution. 



This can be explained on the corpuscular theory in two 

 ways, the first of which involves electrolysis of the salt, 

 whereas the second does not. According to the first the 

 molecules of the salt-vapour dissociate into ions K — a and 

 CI -fa exactly as in a solution. These ions then move to the 

 electrodes and give up their charges, so becoming K and CI, 

 the K being at the negative electrode and the CI at the 

 positive electrode. 



According to the other explanation a molecule of the salt- 

 vapour loses a corpuscle, thus forming two ions, 



KC1— a. and a. 



Then the KC1 — a goes to the negative electrode and only 

 corpuscles go to the positive electrode, so that no separation 

 of the two constituent atoms of the molecule takes place. 



The high velocity of the negative ions compared with that 

 of the positive ions seems to favour the latter view ; but the 

 known cases in which separation of the elements of a com- 

 pound by electrolysis in gases appears to take place strongly 

 support the view that^the ions are similar to those existing in 

 solutions. 



The present experiments do not show what happens to the 

 ions after they have discharged on the electrodes, except that 

 apparently they do not participate any further in the trans- 

 port of the electricity. It is hoped that future experiments 

 will throw more light on this question. 



These experiments were done in the Cavendish Laboratory, 

 and I am greatly indebted to Prof. J. J. Thomson for his 

 advice and encouragement throughout the course of the 

 work. 



