Relative Affinity of some Gas Molecules for Electrons. 229 



especially to show both the sets of grooves side by side con- 

 verging in opposite directions. 



Fiir, 4. 



The reasons why these grooves are on the average of about 

 the same length and occur evenly spaced, start from about 

 the same azimuth and converge, are other noteworthy points 

 of special interest under further investigation. 



University College, London. 



XXIII. The Relative Affinity of some Gas Molecules for Elec- 

 trons. By Leonard B. Loeb, Ph.D., National Research 

 Fellow, University of Chicago *. 



IN a recent paper the writer has shown that in some gases 

 the electron must on the average make a number of 

 impacts n with the molecules of the gas before it can strike 

 one in such a manner as to attach to it to form the negative 

 ion t- In this same paper it was also shown that this 

 quantity n varied with the chemical nature of the gas. It 

 consequently becomes of interest to determine the value 

 of n for a number of the common gases. It is the purpose of 

 this note to discuss briefly the bearing of a recent study 

 of electronic mobilities in N 2 on the determination of this 

 constant, and on the basis of this to evaluate n for a series 

 of gases from the experimental measurements made by the 

 writer and Mr. Wahlin. 



* Communicated by Prof. R. A. Millikan. 



t L. B. Loeb, Phys. Rev. xvii. No. 2, pp. 89-115 (Feb. 1921) ; Proc. 

 Nat. Acad. Sci. vii. No. 1 (Jan. 1921). 



