THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 



OCTOBER, 1910. 



LVIII. The Specific Charge of the Ions emitted by Hot Bodies. 

 — II. By 0. W. Richardson, M.A., D.Sc, Professor of 

 Physics, and E. R. Hulbirt, A.M., Princeton University*. 



IN a previous communication f one of the authors deve- 

 loped a method of measuring the value of ejm for the 

 ions emitted by hot bodies and applied it to the case of the 

 ions of both signs from platinum and carbon. As was to be 

 expected from the results of earlier investigations, the value 

 of the specific charge for the negative ions was found to 

 correspond to that for the negative electrons, whereas the 

 number obtained for the positive ions pointed to bodies of 

 atomic magnitude. Somewhat contrary to expectation, the 

 value of ejm for the positive ions was found to be identical 

 within the limits of experimental error for both platinum and 

 carbon, despite their wide divergence of atomic weight as 

 well as both chemical and physical properties. The values 

 found were also very close to the value given by Sir J. J. 

 Thomson for the corresponding quantity in the case of iron, 

 which appears to have been the only substance for whose 

 positive ions the value of ejm had been determined. The 

 value of ejm in all these cases was about 380 e.m. units, 

 and corresponds to an atomic weight of the carriers of about 

 26, assuming that they carry the same charge as the hydrogen 

 atom in electrolysis. 



* Communicated bv the Authors. 



t 0. W. Richardson, Phil. Mag. [6] vol. xvi. p. 740 (1908). 



Phil. Mag. S. 6. Vol. 20. No. 118. Oct. 1910. 2 



