672 ProE. 0. W. Richardson on the 



together the average values or! m/EL for the positive ions they 

 emit are : — for ZtiCl 2 61 ; for ZnBr 2 50 ; and for Znl 2 42 

 There is thus an apparent decrease in the mass of these ions 

 with increasing atomic weight of the haloid constituent. In 

 the case of zinc chloride it is clear that the bulk of the ions 

 are Zn + . In the other cases they are probably a mixture of 

 Zn + and Zn ++ , but I do not think that this view can be 

 regarded as certain until it can be demonstrated that part of 

 the ionization in the case of the bromide and iodide was not 

 due to alkaline impurities. The breadth of the curves for a 

 given applied potential difference was least for the chloride, 

 and greatest for the iodide, indicating a gradually diminishing 

 degree of purity in the ionization. I was not, however, able 

 to resolve the curves so as to obtain more than one hump 

 with the appliances then available, although the matter will 

 be investigated more fully later. 



The zinc bromide and iodide were supplied by Messrs. 

 Eimer and Amend, with no indication as to their purity 

 beyond the usual guarantee under the Food and Drugs 

 Act. 



Calcium Nitrate. — When calcium nitrate is heated it is 

 converted into the oxide, and, as is well known, this endows 

 the platinum on which it is placed with the power of emitting 

 lar^e numbers of negative electrons. When the nitrate was 

 first heated a large positive ionization was obtained, appa- 

 rently during the conversion of the nitrate into the oxide. 

 The emission then stopped rather abruptly, and further 

 heating of the oxide did not improve matters. On adding 

 more nitrate to the lime and reheating very gocd curves 

 were obtained. These gave the values : — e/m = 222 and 

 m/H = 43'5. This value of m/H is sufficiently close to either 

 Ca + ( = 40) and K + ( = 39), but the comparatively abrupt 

 stoppage of the positive emission when the oxide state is 

 reached is against the impurity explanation in this case. 

 The experiments showed quite clearly that there was no 

 appreciable quantity of Ca ++ . The experiments just de- 

 scribed have demonstrated the existence of the ion Zn + , the 

 probable existence of Ca + and of Zn ++ _, and the possible 

 existence of Mg + . It was clear that more light would be 

 thrown on these phenomena by the investigation of compounds 

 of some of the heavier atoms, such as barium for example, 

 where the possible ions, Ba + and Ba ++ , would be readily 

 distinguishable from ions such as K + and Na + which arise 

 from traces of the salts of the alkali metals which are always 

 liable to be present. 



This part of the investigation has been continued from this 



