Behaviour of Metallic Vapours in Flames. 21 



0*8 cm. long 



88 08x4xlQ- 8 

 ~ 104 450 gm *' 



and the number of atoms in the given space 



88 0-8x4xlQ- 8 

 ~104 450x22xl0~ 23 



= 2-8 xlO 11 atoms. 



Maximum deflexion of galvanometer =18 cm., and 1 cm. 

 deflexion corresponds to a current of 2*88 x 10" 8 amp. 



Potential gradient near positive electrode =6 . 



e r cm. 



We assume that the velocity per , v, of the electrons 



in the flame is 1000 — ' I , as found by Wilson. 



sec./ cm. J 



Let the number of free electrons produced per sec. 



=-n. 

 The elementary charge =e 



= 4'7x 10" 10 c.g.s. electrostatic (Planck). 

 Then the current = 18 x 2'88 X 10" 8 amp. 



= 18 x 2S8 x 3 X 10 9 c.g.s. electrostatic. 

 But the current also = nev 



= 7ix4-7 xl0- 10 x 6x1000. 

 Equating these expressions for the current, we get 

 n = 5*5 x 10 8 electrons, 



while we have already found that the corresponding number 



of metallic atoms is 2*8 x 10 11 . 



5*5 x 10 8 

 .-. each atom is positively charged — ^ — TTmi 



= ptt^ of the time. 

 500 



According to the velocity of migration of the positive 

 carriers, as given by the deflexion of the luminous streak, 



this fraction is ^r, as the velocity of a permanently charged 



cm. 



Sr atom should be 16 '-*, and the velocity as obtained 



sec. 



* See E. N. da C. Andrade, " On the Nature and Velocity of Migration 

 of the Carriers of Electricity in Flames, &c," Phil. Mag. June 1912, p. 865. 



