﻿Electricity in, Flames containing Metallic Vapours. 883 



the values given by Lusby are so much smaller than are 

 given by ^/6. But in the pure flame the gradient decreases, 

 though not very much, so that taking tho gradient just below 



the salt vapour, the velocity per would be relatively 



much larger than that given, Lusby does not give sufficient 

 data to enable me to calculate the velocity according to the 

 views here put forward*, but it looks possible that the \ ! 6 

 law holds roughly throughout the range. 



To explain the large values obtained for the mobility, 

 Lusby assumes that the positive carrier is always an atom of 

 hydrogen. This is quite untenable, as it has been shown here 

 experimentally that the carriers are metallic (§ 7). Particular 

 attention is called to the fact that this was established for 

 two metals (Sr and Na) and to the rough quantitative tests. 

 Of course, none of this criticism of Lusby's paper affects his 

 results, that the velocity is the same for all metals, except at 

 very low temperatures : this result agrees with Lenard's 

 formula for the mobility of a carrier of atomic size (see 

 p. 871), His criticism of Lenard's early results on the 

 deviation of the coloured streak in the electric field, based 

 on the fact that chloroform removes the colour from the 

 streak without much altering the conductivity (Smithells, 

 Dawson, and Wilson) does not seem to me relevant. When 

 glowing electrodes are in the vapour the liberation of an 

 electron from the atom takes place mainly at the electrodes, 

 and it is probable that while chlorine prevents the impact of 

 metal atom against metal atom in the vapour liberating an 

 electron, it does not stop this effect at the electrodes, and 

 thus, while prohibiting " ionization " in the body of the 

 vapour, does not much affect the conductivity "f . 



A short time ago H. A, Wilson J published a paper 

 containing a theoretical treatment of the carriers in flames 

 containing metallic vapours. He makes Lenard's assumption, 

 also made here, that the carrier is only positive during a 

 fraction, /, of the time. Through the further assumption 

 that the velocity of the carrier is inversely proportional to 

 the square root of the atomic weight, he obtains values of /, 

 and he further obtains similar values from the conductivity 

 relations of the salts. The values agree so badly, that it is 

 hard to believe that they furnish a proof of the correctness 

 of the hypothesis. Wilson comes to the conclusion that the 



* The potential curves are all reduced to 100 volts scale. 



t See Lenard, " Uber die El&ktricitatsleitung and Lichtemission 

 metallhaltiper Flam men," Siizmiqsberiehte der Heidelbcrger Acad. 1011. 



\ H, A. Wilson, Phil., Mag, June 1911, p. 711. 



$ M 2 



