,/ ■ 



THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 



NOVEMBER 1911, 



LXVI. The Positive Ionization from Hot Salts. By 0. W. 

 Richardson, Professor of Physics, Princeton University*. 



TN two papers published in the Philosophical Magazine for 

 December 1910 the author described experiments which 

 were made in order to determine the value of the specific 

 charge (e/m) of the positive thermions emitted by the salts 

 of the alkali metals. The results of the experiments showed 

 that the positive ions, in each case, were atoms of the basic 

 metal carrying a single electronic charge. Since then the 

 investigation has been extended in different directions. 



The Specific Charge of the Ions. 



In the first place the value of e\m has been measured for 

 the salts of a number of other elements. At the end of the 

 second of the papers referred to, it was pointed out that one 

 very interesting question which arises is whether the salts of 

 polyvalent elements will emit ions carrying multiple electronic 

 charges. The early work of Beattiet showed that compounds 

 of zinc were very efficient in producing positive ionization, 

 whilst the work of Arrhenius, H. A. Wilson, and others on 

 the conductivity of flames and salt vapours had shown that 

 similar properties were to be expected of the salts of the alka- 

 line earth metals. Attention was therefore directed to the salts 

 of the zinc and calcium groups of metals. All these metals 



* Communicated by the Author. 



t Phil. Mag. [5] vol. xlviii. p. 97 (1899). 



Phil, Mag. S. 6. Vol. 22. No. 131. Nov. 1911. 2 Y 



