Ionization from Heated Platinum, 



171 



electrons to the cold electrode during a temporary heating. 

 After a wire, for example, giving a slow decay with time 

 current of 0*8 div. per sec. at +200 volts and 453° C, was 

 heated for an hour at 540° 0. the following current-time 

 readings were taken, when the temperature of the wire was 

 again made 453° C. at + 200 volts. 



Current in 

 divisions per 

 second 



'.'J 



19-9 156 129 6-5 4-2 2*8 1'8 1' 



1-00 



Time 1 Q 



(minutes) J 



10 



25 35 45 60 



85 



Again, in a particular case the current, after continued 

 heating at 388° C, showed a nearly constant value of 0*7 div. 

 per sec. at + 400 volts. The w^ire was then heated for 30 

 minutes at 598° 0. and —400 volts, the negative emission 

 being measurable at this temperature. On returning to 

 388° C. and +400 volts, the initial current was found to be 

 equal to 14 div. per sec, or about twenty times its previous 

 value. This large current fell away fairly rapidly with 

 time at the lower temperature (388° C), as is shown by the 

 folio win 2 data. 



Current in 

 divisions per 

 second 



14 10 8 51 38 26 20 145 105 100 



Time 



(minutes) 



} 



10 25 35 45 60 



85 



100 



We can explain these results if we suppose that the in- 

 creased positive ionization, or, as we may call it, the 

 " induced leak," is due to some substance which gradually 

 decomposes under the influence of heat into at least one 

 positive ion. The reaction, assumed monomolecular, may 

 be represented by the equation P = ?>I4-Q, where P repre- 

 sents the unknown substance, n the number of positive ions 

 produced by each molecule of P, and Q represents other 

 products if existing. From the laws of chemical dynamics 

 we may write : 



and hence 



dt 

 P =A,*-* . 



