714 



Prof. H. A. Wilson on the Velocity of the 



where q 

 per sec. 



than in a Bunsen flame, so that the values found for fk x 

 should be much less, as was found to be the case *. 



The relative values of the fraction / for different salts can 

 be deduced from the conductivities which they impart to the 

 flame. In the determination of fk x the concentration of the 

 metallic atoms which move down the flame is extremely 

 small, not enongh to appreciably colour the flame except in 

 the case of sodium. The equilibrium between the atoms and 

 negative electrons will, therefore, be determined by the 

 equation 



q = BQ$—n) = ccnm, . . . . (1) 



is the number of positive ions produced per c.c. 



by ionization of the metal atoms, 1ST the total 

 number of metal atoms present per c.c, n the number of 

 metal atoms which are ions per c.c, m the number of nega- 

 tive electrons per c.c, and ft and a are constants, m will be 

 large compared with n because the ions of the flame will be 

 much more numerous than the ions from the metal vapour. 

 Now/=?i/N, so that equation (1) becomes 



for another salt we have in the same way 



/3'(1 -/')=«'»«/'• 

 Hence 



& f i-/' , 9 . 



ap-fl-f W 



When the conductivities imparted to the flame by different 

 salts were compared, the salts were present in comparatively 

 large concentrations, and the number of ions due to the salts 

 was large compared with the number due to the flame gases. 

 In this case, therefore,' 



q=/3QS-n), 



and for another salt having the same molecukr concentration 



? ' = /3'(N-n'). 



Here n will be small compared with N, so that approximately 



£_£ 



<f~0- 



(3) 



Then (2) and (3) give 





i-/' 



i-/ 



H. A. Wilson, Phil. Trans. A. ccxxxvii. (1899). 



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