Cathode Disintegration in a Vacuum Tube. 415 



(iv.) The conception o£ the " unit " is extended. In this 

 form, units promise to become successful in the 

 explanation of the purely optical effects. 



In conclusion I wish to express my best thanks to Sir J. J. 

 Thomson for his kind interest in these experiments. 



'Cavendish Laboratory, Cambridge. 

 August 1913. 



XLV. Cathode Disintegration in a Vacuum Tube. By A. M. 

 Tyndall, D.Sc. [Lecturer in Physics in the University of 

 Bristol), and H. G. Hughes, B.Sc* 



^T^HE disintegration or " spluttering " of the cathode in a 

 JL vacuum tube has been the subject of much investi- 

 gation. A comprehensive summary and discussion of the 

 results which have been obtained has been published by 

 Kohlschutter f , and to his paper a complete bibliography is 

 appended. 



In the following paper an account is given of some further 

 experiments on the influence of certain factors on disin- 

 tegration. The effects of some of these factors have already 

 been a subject of investigation, as may be seen by reference 

 to the literature of the subject, but it was felt that there 

 were a number of points upon which further information 

 was necessary. 



The factors dealt with below are (a) the duration of the 

 discharge ; (b) the previous history of the cathode ; (c) the 

 pressure and nature of the gas ; (d) the current density ; 

 and (e) the cathode fall of potential. A summary of the 

 conclusions which have been arrived at is given at the end 

 of the paper. 



Method of Experiment. 



The amount of disintegration was measured in all cases 

 by the loss of weight of the cathode. During discharge it 

 was necessary in general to control and measure pressure, 

 current, and cathode-fall of potential. A diagram of the 

 experimental arrangements is shown in the figure. 



D is the discharge-tube which could be opened at the 



* Communicated by the Authors. 



t Kohlschutter, Jahrbuch d. Had. u. JZlectronik, ix. p. 355 (1932). 



2 F 2 



