981 Prof. 0. W. Richardson on the Positive 



Preliminary Experiments. 



On account of the very close similarity in the properties 

 of the alkali metals ami their compounds, we should expect 

 that the sulphates of the different alkali metals would give 

 rise to positive ions whose values of e/m and m would be 

 determined by t ho atomic weight of the metal under 

 investigation. This conclusion is to be expected whether 

 the ions contain mere than one chemical atom or not ; for 

 it is to be expected, from the similarity of the properties 

 of the alkali metals already alluded to, that the ions 

 from the different metal- will be similarly constituted what- 

 ever their constitution may be. For example, if the ions 

 from lithium sulphate were molecules of Li 2 S0 4 which had 

 lost a negative electron, we should expect the ions from 

 jsium sulphate to be molecules of K 2 S0 4 less a negative 

 electron : if the ions from lithium sulphate were atoms of 

 lithium less a negative electron, we should expect the ions 

 from potassium sulphate to be atoms of potassium less a 

 negative election, and so on. AVe should thus expect the 

 values of e/m to exhibit a regular diminution, and those of m 

 a regular increase in proceeding from lithium sulphate to 

 csesium sulphate. The difference of the values in these 

 sequences will, of course, be greatest if the ions are the atoms 

 of the element- who-'" compound- are used : if the ions are 

 themselves of a compound nature, the differences will he not be 

 so great, hut will he in the same direction. Thus both the abso- 

 lute valuesofe/wi and in and their relative values, also, should 

 afford us valuable information as to the structure of these ions. 

 The first experiments made were of a rather qualitative 

 character. The method was adopted of comparing the de- 

 flexion of the ions of the salt used with that of the platinum 

 ions from the same strip and in the same magnetic field. It 

 was found that the ions from sodium sulphate were deflected 

 rather more, and those from potassium sulphate rather less, 

 than those from platinum. This was in accordance with 

 previous expectation. A surprise was in store, however, 

 when lithium sulphate was tried. It was found that on the 

 first trial the ions from this substance were deflected to 

 almost exactly the same extent as those from platinum but 

 rather less if anything, whereas on the view expressed above 

 the deflexion for the ions from lithium sulphate should have 

 been very much bigger than for those from the two metals 

 of higher atomic weights. Instead of this, the values for 

 lithium sulphate were between those for the sulphates of 

 sodium and potassium. 



