990 Prof. 0. W. Richardson on the Positive 



agreement with the view that the initial ionization is due* 

 principally to the admixture of salts o£ this element, perhaps 

 with some sodium in addition. The value 41*8, for the inner 

 of the humps which developed after the twelve hours heating, 

 again is of approximately the same magnitude, pointing to 

 the presence in smaller relative amount of the same impurity. 

 The value (5"5), calculated from the two outer humps, agrees 

 satisfactorily with the atomic weight of lithium (7*05). A 

 still better agreement is obtained after the inner humps have 

 disappeared, and we obtain the value of ?/? which presumably 

 corresponds to the pure lithium Fait. The value after 44 

 hours healing was found to be 5*57, and after 52 hours 

 heating 7*43. The mean of these values is 6'5 instead of ?•()"). 

 The value (20*6) obtained alter 70 hours heating is what, we 

 should expeet if it were due to the platinum ions, for which 

 //< was Found to he 32'5, mixed with a certain amount of the 

 more deviable ions from the lithium salt. Thus the view we 

 have taken of these effects gives a satisfactory account of the 



phenomena exhibited bv lithium sulphate. The position la 

 still further strengthened when the salts of the other alkali 

 metals are examined. 



Sodium Sulphate. 



The specimens of sodium and potassium sulphates used 

 were presented to the author several years ago by Professor 

 H. A. Wilson. They had been specially prepared for use in 

 obtaining standard temperatures from their melting-point, 

 and are believed to be very pure. At any rate, the sodium 

 sulphate is not likely to contain anything with more capacity 

 for emitting ions than itself, with the possible exception of 

 traces of potassium sulphate. We should therefore expect 

 that sodium sulphate would behave quite differently from 

 lithium sulphate. The deflexion of the maximum by the 

 magnetic field ought to be quite constant, except in so tar as 

 any trace of potassium sulphate present might make the 

 deflexion a little smaller at first than later, 'ihere ought to 

 be no development of widely divergent humps as in the case 

 of the lithium sulphate. As a matter of fact this is exactly 

 what was observed. 



As before, two sets of curves for the initial ionization 

 from the platinum strip (a fresh one) were taken. The 

 distance between the maxima for one set of curves was 1'9# 

 turns of the screw and for the other 2*04 turns, the mean 

 being 2*00 turns. The value of z was '492 cm. The strength 

 H of the magnetic field in this set of experiments was 

 4650 lines per cm. The above numbers give m = 33'7, which 



