368 



PHENOMENA, ATOMS, AND MOLECULES 



Curves IV and V in Fig. 24 and curve IV in Fig. 23 are examples of 

 Case I. For each point the completely coated filament was suddenly raised 

 to the indicated temperatures by a condenser discharge and held there by 

 the proper current. 



70 



60 



■50 



H 



40 



30 



— O J .e -J ■■^ Q -5 -6 .7 .<3 .9 

 Fig. 25. Values of H, the relative rate of increase of Vo with 6, defined by Eq. (40) . 



The full. line curves IV and V in Fig. 24 were calculated accurately 

 by Eq. (42), by using |x = 6.2 X 10^^, a^i = 4.8 X 10^*, and for curve IV, 

 ^00 = 0.72, H = 33.9 at 530°, while for curve V, ^00 = 0.372, H = 30.4 

 at 704°. For Fig. 23 (curve IV), ^00= 0.056 at 970°. As these values of 

 ^00 were calculated from the values of \i, no adjustable parameters have 

 been used in the construction of these curves. 



Case II. Starting with 6 =0 at f = o integration gives (if we neglect 

 exp { — HOco) compared to unity) : 



(43) 



exp { — jjLlIt/aAi) 



= exp{-Iie)-expi-HdJ. 



The curve OPNP'C in Fig. 26 is the curve given by this equation. 

 Except for a short transition region the curve nearly coincides with its 

 two asymptotes OA and BC. It is therefore more convenient to express it 



