﻿774 Dr, A. Sellerio on the Repulsive Effect upon 



In my paper on the arc Hg + /C", above mentioned, 

 assuming for the vapours issuing from the anode the 

 boiling temperature 357° C. = 630abs., I have found a value 

 V = 1000 cm. /sec., whilst at the same temperature the atomic 

 speed would be 



18-39 . 10* ^/Jg ^/|g = 28,000 om./seo. 



Even when the assumed temperature at the Hg crater is 

 really higher, both the considered speeds remain too different 

 from each other. 



9. With a C/C arc, if the carbon consumption did occur 

 only by evaporation in the crater, we should have, denoting 

 with d the mean vapour density, a loss of mass per second, 



m = Aval. 



As, however, in an ordinary arc the carbon out of the 

 crater is consumed also by burning in the air, we must 

 write 



m > Avd, 

 whence 



V = Ad (5) 



With reference to some of Duffield's researches *, we can 

 take for the anode with i = 8 amp. and L = 3 mm., 

 m = 135 . 10~ 5 g./sec, the area A being 0'24 cm. 2 , as shown 

 in Table II. The density of the carbon vapours at 4000° 0., 

 being taken as 0*00009, the abs. density of H 2 at 0° C, 

 becomes 



, 12 0-00009 Q " 1A _ 5 



^=¥r^ooo =3,45 - 10% 



+ 273 

 then we have from (5) 



v< 650 cm./sec, 



a velocity range far removed from the atomic speed 2*97 . 10 5 

 mentioned above. 



We will calculate in a simple manner what should be the 

 average velocity v, so as to give account of the observed 

 effect P. 



* " Consumption of Carbon in the Electric Arc," Koy. Soc. Proc. A. 

 vol. xcii. p. 122 (1915). Above data are taken from a " Note upon the 

 Alternating-Current Carbon Arc," by Prof. Duffield and Mary D. Walker, 

 Phil. Mag. vol. xl. p. 781 (1920). 



