100 MI-SSKS A SMITIIKU.S. II M. l> \\VSON, AND H. A. AVII.SoX: KU-XTUICAL 



We do not propose to enter into a discussion of the cause of this unipolar conduc- 

 tion, which has already been the subject of frequent, but not very fruitful, research. 

 If it be due to the assymmetry of the electrode system, either in regard to their size 

 or position in the flame, and if it be connected with the well-known influence of ultra- 

 violet light or of a high temperature in facilitating the discharge of negative elec- 

 tricity, the circumstances of our experiments offer no obstacle to such an explanation. 

 But they do not throw any fresh light on the phenomenon, and it is outside the 

 scope of our enquiries to discuss it. 



Concentration of Salt Vapour in the Flame. 



To obtain an estimate of the quantity of salt vapour entering the flame in our 

 experiments, we adopted the method used by ARRHENIUS. 



The cone separating apparatus was removed, and the flame obtained at the orifice 

 of the tube I (fig. 3). A bead of sodium sulphate was held in the flame for a 

 measured interval of time, during which the light intensity was compared photo- 

 metrically with that of a standard candle. The loss in weight of the" bead was 

 determined. By spraying a sodium sulphate solution of suitable strength in our 

 apparatus, a flame of light intensity equal to that containing the bead was obtained. 



The following numbers give the results. They afford, at the same time, a confir- 

 mation of the statement of GOUY, that above a certain limit the light intensity of a 

 flan le coloured by the vapour of an alkali salt varies approximately as the square root 

 of the amount of salt introduced. 



Experiment 1. Loss of weight of bead per minute, '00161 gram. Intensity of 



light, 1-56. 

 Experiment 2. Loss of weight of bead per minute, '00325 gram. Intensity of 



light, 2'00. 

 Experiment 3. Solution sprayed ^ normal sodium sulphate. Intensity of 



light, 1-53. 

 Experiment 4. Solution sprayed | normal sodium sulphate. Intensity of 



light, '95. 



From Experiments 1 and 2 we have 



Ratio of light intensities 1-3 



Square root of ratio of concentrations 1 '4 



From Experiments 3 and 



I lutio (.flight intensities . . . 

 Square root of ratio of concentrations 



1-6 

 1-6 



Tin- amount of salt supplied to the flame per minute by the half normal sodium 

 sulphate solution may therefore be taken as "0016 gram, and as a rough approxima- 



