Ionization from Heated Platinum. 179 



than had been just previously obtained at this lower tem- 

 perature. These results are in agreement with those given 

 in Curve I., fig. 1. 



Table II. 



Temp. = 738° C. 

 V = + 200 volts. 



Heated 10 minutes 

 at 765° C. and 



V=0; thermionic 



currents read at 



738° C. 



Temp.= 765° C. 

 V = 4- 200 volts. 



Heated 10 minutes 



at 786° O. and 



Y= 0; thermionic 



currents read at 



765° C. 



Time 

 (Min.). 



Current. 



Time 

 (Min.). 



Current. 



Time 



(Min.). 



Current. 



Time 

 (Min.). 



Current. 







25 



45 



7 

 10 



32 

 2-5 

 20 

 1-9 

 1-8 

 ... 







1-5 

 25 

 4 

 10 



u 



52 



33 



26 

 2-45 



2-28 

 220 





 1 

 2 

 3 

 5 

 8 



20 

 22 

 20 

 22 

 2-2 

 22 







1 

 2 

 4 

 7 

 10 



0-72 

 0-67 

 045 

 044 

 0-45 

 044 



(Note. — The wire was in such a condition that very small 

 ionization currents were obtainable. The readings given in 

 Table II. were obtained after Curves I. and II., fig. 1.) 



IV. Increased Emission produced by heating in a 

 Bunsen Burner. 



Following Curves I. and II. of fig. 1 and before the heating 

 of the wire in the Bunsen burner, the following values of 

 the positive currents were obtained at the temperatures 

 shown : — 



Temperature, ° C. 



628 



654 



668 



714 750 765 



775 812 822 



Current (div. ] 

 per sec.) at I 

 V= +200 volts. J 



096 



23 



6-2 



10 18-2 24 



43 110 220 



The wire was then removed and heated in the reducing- 

 flame of the Bunsen burner for 10 minutes. The same 

 procedure was then followed as in obtaining Curve L, fig. 1, 



N2 



