Positive Ionization from Hot Salts. 703 



The chemistry of the emission of positive ions from salts is, 

 however, still unsolved. The reaction might for example be 

 a catalytic one of the type 



Ba + Pt=Ba + + E + Pt 



where E stands for a negative electron which goes over to 

 the platinum and carries the current, the metal (barium in 

 this case) being liberated by ordinary chemical actions 

 which do not involve the transference of electric charge. 

 Personally, however, I am inclined to suspect that in some 

 way ions play a very fundamental and important part in 

 chemical actions at high temperatures, just as they do in 

 solutions at ordinary temperatures. 



On the whole there is no reason for supposing that there 

 is any essential difference between the mechanism of the 

 large positive emission from freshly heated metals and that 

 observed with salts. They both have the same general 

 characteristics, namely : (1) an initial exponential decay 

 with time followed by a slowing off* ; (2) occasionally the 

 variation with time is more complicated, an intermediate 

 rise to a maximum being observed f ; (3) the decay with 

 time is quickest when the body is positively charged and is 

 retarded by a negative charge f ; (1) both vary with the 

 temperature according to a formula of the type a6h~ b < 9 , where 

 a and b are constants § ; (5) in neither case is there any 

 simple relation between chemical action and thermionic 

 emission || ; and (6) the kinetic energy of the thermions is 

 much the same in both cases IF . 



The very small ionization which is observed when an 

 " old " platinum wire is heated in different gases { and 

 which is a function of the pressure is, I think, quite different 

 from anything which has hitherto been observed with salts. 

 It seems probable that in this case the positive ions will turn 

 out to be atoms of the surrounding gas, but all the existing 

 evidence as to their nature is indirect. The difficulty in 

 measuring the value of e/m for them lies in the smallness of 

 the currents. 



In conclusion I wish to thank my assistant, Mr. E. S. 

 Taylerson, and my former assistant, Mr. Cornells Bol, for 

 their help in taking the observations. 

 Palmer Physical Laboratory, 

 Princeton, N. J. 



* O. W. Richardson, Phil. Mag. [6] vol. vi. p. 80 (1904). 

 f O. W . Richardson, C. R. Liege, p. 50 (1905). 

 X O. \V. Richardson, Phil. Trans. A. vol. ccvii. p. 1 (1906). 

 § O. W. Richardson, B.A. Reports, Cambridge, 1904, p. 472. 

 || R. J. Strutt, Phil. Mag. [6] vol. iv. p. 98 (1903). 

 •fl F. C. Brown, Phil. Mag. [6] vol. xviii. p. 649 (1909). 

 3 A2 



