228 



Dr. H. A. Wilson. On the Electrical 



u On the Electrical Conductivity of Air and Salt Vapours." By 

 Harold A. Wilson, D.Sa, M.Sc., B.A., Allen Scholar, Caven- 

 dish Laboratory, Cambridge. Communicated by Professor 

 J. J. Thomson, F.E.S. Eeceived March 14 — Eead March 28, 

 1901. 



(Abstract.) 



The experiments described in this paper were undertaken with the 

 object of obtaining information on the variation of the conductivity of 

 air and of salt vapours with change of temperature, and on the maxi- 

 mum current which a definite amount of salt in the form of vapour 

 can carry. They are a continuation of the two researches* on the same 

 subject published in 1899. 



In the paper on the Electrical Conductivity and Luminosity of 

 Flames (loc. cit.) some observations on the variation of the conductivity 

 with the temperature at different heights in the flame are given. 

 They indicate a rapid increase in the conductivity with rise of tem- 

 perature. 



The method employed in the experiments described in the present 

 paper was the following : — 



A current of air containing a small amount of a salt solution in 

 suspension in the form of spray was passed through a platinum tube 

 heated in a gas furnace ; this tube served as one electrode, and the 

 other was fixed along its axis. The temperature of the tube was 

 measured by means of a platinum platinum-rhodium thermo-couple, 

 and the amount of salt passing through the tube was estimated by 

 collecting the spray in a glass-wool plug. 



From the temperature variation of the conductivity the energy 

 required to produce the ionization can be calculated, and this com- 

 pared with the energy required to ionize bodies in solutions. 



Since the publication of the researches just referred to, several 

 papers! on the conductivity of salt vapours in flames by Dr. E. Marx 

 have appeared. The first part of the present paper contains a 

 discussion of some of Marx's conclusions, which bear on my previous 

 work. 



The rest of the paper is divided into the following sections : — 

 (1.) Description of the apparatus used. 



* " The Electrical Conductivity and Luminosity of Flames containing Vaporised 

 Salts," by A. Smithells, H. M. Dawson, and H. A. Wilson, < Phil. Trans.,' A, 1899; 

 " On the Electrical Conductivity of Flames containing Salt Vapours," by Harold 

 A. Wilson, ' Phil. Trans.,' A, 1899. 



f "Ueber den Potentialfall unci die Dissociation in Flammengasen," Von Erich 

 Marx, ' G-esellschaft der Wissenschaften zu Grottingen,' 1900, heft 1 ; ' Annalen 

 der Physik,' 1900, No. 8. " Ueber das HalPsche Phiinomen in Flammengasen," Von 

 E. Marx, ' Annalen der Physik,' 1900, No. 8. 



