Behaviour of Metallic Vapours in Flames, 33 



Difference of potential between electrodes 11,000 volts. 

 Distance apart of electrodes 5*5 cm. 



Distance apart of 

 probe wires. 



Pressure. 



Potential gradient 

 in flame. 



6-4 mm. 



6-4 „ 

 6-4 „ 



5'1 „ 

 5'1 „ 



76 cm. Hg. 



50 „ 

 30 

 76 

 28 



1160 ™L* 



cm. 



840 „ 



590 ,. 

 1110 „ 



400 „ 



From these experiments we have the variation of the 

 gradient of potential in the flame at reduced pressures. The 

 deflexion of the streak remained about constant when the 

 potential of the insulated electrode was constant, as found by 

 Ebert. The velocity of the flame was not actually measured: 

 according to Ebert it varies only slightly with the pressure 

 in this range, and extrapolation of my measurements at high 

 pressure gives a variation of less than 10 per cent, in the 

 given range. From these results the velocity of migration 

 at low pressures was calculated. 



Pressure. 



Velocity of 

 . migration. 



Product. 



76 cm. Hg. 



50 

 30 



90 arbitrary unite. 

 120 „ 



200 „ 



684 

 600 

 600 



The velocity of migration is again inversely as the 

 pressure. Thus from 30 cms. Hg to 4 atmospheres the 

 velocity of migration of the positive carriers of the first kind * 

 is inversely proportional to the pressure. 



* See E. N. da 0. Andrade " On the Nature and Velocity of Migration 

 of the Carriers of Electricity in Flames," Phil. Mag. June 1912, p. 866. 



Phil Mag. S. 6. Vol. 24. No. 139. July 1912. 



D 



