522 



TATE AND FOOTE : RESONANCE POTENTIALS 



So 



this value, viz. 0.8 volts. The mean value thus obtained for 

 curves 3 to 7 was 0.80 volts. 



Without changing conditions in any way the curves 9, 10, and 

 11, figure 3, representing the variation in total current from the 

 hot wire with accelerating potential were obtained. Curves 9 a, 

 10 a, and 11a are sections of the curves 9, 10, and 11 plotted on 

 the same scale of coordinates used in figures 2 and 3. It is to be 



noted that there is no sudden change in 

 the total current at points corresponding 

 to a and b, etc., on the other curves. 

 This indicates that no ionization results 

 from the inelastic impact which occurs 

 at 2.12 volts. There is, however, a 

 sharp increase in current at an average 

 applied potential of 4.33 volts. Correcting 

 for the initial velocity as determined 

 above gives 5.13 volts for the average 

 value of the ionizing potential. 



Simultaneously with the rapid increase 

 in current at 4.33 volts there appeared a 

 bright yellow glow about the hot wire. 



It is to be emphasized that the critical 

 points were chosen by plotting all curves 

 on the same scale and estimating where the 

 actual curves deviated by a constant pre- 

 determined small amount from the curve 

 extrapolated beyond the critical point. 

 7 Since we are dealing here with differences 

 Potent/a/ (Volts) between similarly chosen points the ele- 

 Fig. 4. Examples of dis- ment of arbitrariness in their choice is 

 continuous "total current" largely eliminated. The final results are 



tabulated in table 1. 

 With a rather high vapor pressure of sodium the total current 

 curves showed a discontinuous break (see fig. 4) at some inde- 

 terminate potential. The current jumped to a very high value 

 and, as the potential was decreased, remained very large until 

 the potential was considerably lower than that at which the 



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