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II. Some Experiments on the Electrical Behaviour of Metallic 

 Vapours hi Flames. By E. N. da G. Andrade, Ph.D., 

 B.Sc, 1851 Exhibition Scholar of University College, 

 London *. 



§ 1. Introduction. 



TFVEE following work, carried out in the Radiologisches 

 JL Institut of Heidelberg, falls into two parts, the first 

 part (§ 2-§ 5) being concerned with some of the properties — 

 de viation in the electric field f, conductivity, light-emission 

 — of metallic vapour in the Bunsen flame; the second part 

 (§ 6-§ 11) deals with the variation of the deviation of the 

 streak of vapour with pressure, both when this is above and 

 below atmospheric, and was undertaken with the particular 

 object of throwing light on the mechanism of the liberation 

 of the electron from the metallic atom in the flame. 



The first experiments to be described show that in certain 

 circumstances there exist negatively-charged luminous metal 

 atoms in the flame. The conductivity of the vapour has been 

 measured under new conditions, and hence an estimate of 

 the number of free electrons produced per second in the 

 vapour made. A proportion ality between luminosity and 

 conductivity has been found. 



In the second part, the chief result has been to show that 

 the velocity of migration of the positive metallic carriers is 

 inversely proportional to the pressure, which leads to the 

 conclusion that the fraction of time during which a metal 

 atom in the luminous streak is positively charged (we make 

 the assumption % that the atom is alternately positive and 

 neutral) is independent of the pressure. As a theoretical 

 result of this we have that the impact of metal atom against 

 metal, as distinct from that of metal atom against gas molecule, 

 is mainly responsible for the liberation of the electron. 



Measurements on the variation of conductivity and light 

 emission with pressure are also described. 



§ 2. General behaviour of the Luminous Streak 

 in the Electric Field. 



As it was desired to measure the deflexion of the luminous 

 streak of metallic vapour in the flame with a range of 

 pressures, it was advisable to study the phenomena generally 



* Communicated by Prof. Sir J. J. Thomson. 



t The deviation in an electric field of the streak of metallic vapour 

 formed when a bead of metallic salt is brought into the flame which was 

 observed by P. Lenard, Ann. der Physik (4) ix. p. 642 (1902). 



% Made by Lenard for the positive carriers in flames {he. ctt.), and 

 subsequently by W. Wien for canal rays. 



