LOOO Positive Thermions emitted by Salts of Alkali Metals. 



expect that all the salts of a given alkali metal would emit 

 positive ions having a value of elm which is the same for all 

 of them and is eqnal to the value of that quantity for the 

 salts of the corresponding metal in electrolysis. 



Experiments to te?t this point were made with sodium 

 fluoride ami sodium iodide as well as sodium sulphate. 

 S tdium salts were chosen as it is desirable to use an element 

 of low atomic weight ; since the influence of the non-metallic 

 part of the compound will then he relatively greater. 

 Lithium was rejected on the ground that its salts are liable 

 to coni i i 11 those o£ the (dements of higher atomic weight as 

 imparities, and the ionization from these is apt to mask that 

 from the lithium salt. The fluoride and iodide were chosen 

 as they differ widely in their molecular weight from each 

 other and in chemical constitution from the sulphate. 



Measurements of the e m Eor the positive ions from sodium 

 fluoride were made after two hours, four and a half hours, 

 sixteen hours, and thirty-six hours heating. Similar measure- 

 ments with sodium iodide were made after two hours, six 

 hours, and eighteen hoars. In aeither ease did any of the 

 values obtained differ from the electrolytic value for sodium 

 Salts by more than five per Cent., which is about the order of 

 accuracy claimed lor the observations. 



We therefore conclude that the positive ions emitted by 

 the -alt- of the alkali metals depend only on the nature of 

 tle> constituent metal and are, in fact, atoms of the metal 

 which have losl a negative electron. 



Since the alkali metals are monovalent we should expect, 

 on chemical grounds, that their ions would contain only one 

 unit of electronic charge. In the case of the metals of 

 higher valency we stand a better chance of getting ions 

 which carry more than one unit of charge. Although, in 

 any case, multiply charged ion- will have to contend with a 

 much stronger tendency to recombination, and will, on that 

 account, be less likely to be liberated than singly charged 

 ion-. For these reasons the nature of the positive ions 

 liberated by the salts of the other metals when they are 

 heated is of great interest, and experiments on them are now 

 being made by the same method. 



Palmer Physical Laboratory, 

 Princeton, X.J. 



