PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



PHILOSOPHICAL SOCIETY OF WASHINGTON 



82 2D MEETING 



The 822d meeting was held at the Cosmos Club, October 25, 1919, 

 and was called to order at 8.25 p.m. by President Humphreys. At- 

 tendance, 52. 



J. H. Bellinger: Principles of radio transmission and reception 

 with antenna and coil aerials. 



The paper was illustrated by lantern slides and was discussed by 

 Messrs. G. W. Littlehales, W. J. Humphreys, C. E. Mendenhall, 

 William Bowie, and General G. O. Squier. This paper has been 

 abstracted in this Journal (9: 641. Dec. 4, 1919). 



F. L. MoHLER, Paul D. Foote and H. F. Stimson: Ionization and 

 resonance potentials for electrons in vapors of lead and calcium. This 

 paper was presented by Mr. FooTE and was illustrated by lantern 

 slides. 



Measurements of electron currents in three-electrode vacuum tubes 

 of the type previously described have been made in vapors of lead and 

 calcium. The lead and calcium were boiled in porcelain tubes at tem- 

 peratures of about 1000° and 900° C, respectively. Current-voltage 

 curves in lead showed a resonance potential of 1.26 volts and an ioniza- 

 tion potential of 7.93 volts. Applying the quantum relation Ve = 

 hv we find that 1.26 volts corresponds, within experimental error, to the 

 frequency of a strong infrared spectrum line at X = 10,291 A, giving 

 a theoretical value of the resonance potential 1.198 volts. 



In calcium two resonance potentials were found at 1.90 volts and at 

 2.85 volts, of which the first is the more prominent. Ionization oc- 

 curred at 6.01 volts. The ionization potential corresponds to the 

 limit of the principal series 1.5 5, X = 2027 A, giving as the theoretical 

 value V = 6.081 volts. The first resonance is determined by the Hne 

 1.5 5 — 2 ^2, X = 6572.78 A, V = 1.877 volts. ^The second resonance 

 corresponds to the line 1.5 5 — 2 P, X = 4226.73 A, V = 2.918 volts. 



The spectral relations of the first resonance potential and ionization 

 potential are analogous to the relation found with other metals in this 

 group. Work of other observers shows that both the lines 1.5 vS — 2 P 

 and 1.5 S — 2p2 appear below the ionization potential in most metals of 

 this group. 



This paper was discussed by Mr. White. 



E. C. Crittenden, Corresponding Secretary. 



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