120 



Mr. H. A. Wilson. On the Electrical 



" On the Electrical Conductivity of Flames containing Salt 

 Vapours." By Harold A. Wilson, B.Sc. (Lond. and Vic), 

 1851 Exhibition Scholar. Communicated by Professor J. J. 

 Thomson, F.K.S. Eeceived March 10— Bead April 27, 1899. 



(Abstract.) 



The experiments described in this paper were undertaken with the 

 object of following up the analogy between the conductivity of salt 

 vapours and that of Bontgenised gases, and especially of getting some 

 information about the velocities of the ions in the flame itself. 



They are to some extent a continuation of the research of which 

 an abstract has already been published in the 'Proceedings of the 

 Boyal Society.'* 



The paper is divided into the following sections : — 



(1) Description of the apparatus for producing the flame. 



(2) The relation between the current and E.M.F. in the flame. 



(3) The fall of potential between the electrodes. 



(4) The ionisation of the salt vapour. 



(5) The relative velocities of the ions in the flame. 



(6) The relative velocities of the ions in hot air. 



(7) Conclusion. 



The apparatus used for producing the flame was similar in principle 

 to that used in the investigation referred to above. Carefully regu- 

 lated supplies of coal gas and air were mixed together along with spray 

 of a salt solution, and the mixture burnt from a brass tube 0*7 cm. in 

 diameter. 



The flame thus obtained was steady, and measurements of its con- 

 ductivity, when a particular salt solution was sprayed, did not differ 

 more than 1 or 2 per cent, on different days. The height of the inner 

 sharply defined green cone was 1*5 cm., and that of the outer cone 

 7-5 cm. 



The current between two gauzes of platinum wire, each 14 cm. in 

 diameter, and placed horizontally one above the other in the flame, was 

 measured for E.M.F.'s up to 800 volts, and with various distances 

 between the gauzes. 



The current with a large E.M.F. was found to be independent of the 

 distance between the electrodes when the upper electrode or gauze 

 was positively charged, provided that the distance between the elec- 

 trodes was not so great that the upper one was in the cooler parts of 

 the flame near its point. When the upper gauze was comparatively 



* " The Electrical Conductivity and Luminosity of Flames containing Vaporised 

 Salts," by Arthur Smithells, H. M. Dawson, and H. A. Wilson, * Eoy. Soc. Proc.,' 

 toI. 64, p. 142. 



