III. The Electrical Conduct ii-i'/i/ n,l />/;mw>y of Flanii'x containing Vnj,,., 



Saltt, 



lly AuTiiru SMITIIKI.US, H. M. DAWSON, and H. A. WILSON, The 



Yorkshire College, Leeds. 



Communicated by Sir H. E. ROSOOE, F./f.\ 

 Received October 24, Road Novomlxsr 17, 1898, Revised February 9, 1899. 



THE colour imparted to flames by the salts of an alkali metal is generally considered 

 to be duo to the metal existing in the state of incandescent vapour, but there does 

 not appear to ta any settled opinion as to the process by which the metal is set free 

 from its salts. It is frequently assumed that the high temperature reigning in the 

 flame dissociates the salt. There is, however, little, if any, independent evidence 

 in favour of this view. Another explanation ascribes the liberation of metal to 

 chemical decomposition. Thus, in the case of sodium chloride introduced into the 

 flame of a Bunsen burner consuming coal-gas, it would be supposed that in the first 

 instance the water vapour present would act in accordance with the following 



equation : 



NaCI + H,O = NaHO + HC1. 



The sodium hydrate (or possibly oxide) so produced would then l)e deprived of its 

 oxygen by reducing gases (hydrogen, hydrocarbon, carbon monoxide) existing in the 

 flame. A somewhat similar explanation would have to be applied t the flames of 

 hydrogen, carbon monoxide, and cyanogen, though, in the case of the last two gases, 

 the steps of the processes are still more hypothetical. 



It is a noteworthy fact that the coloration of flames by alkali salts extends up to, 

 and even beyond, the outer margin of the visible region of combustion, where the 

 flame gases are usually considered to be fully oxidised and where free atmospheric 

 oxygen exists. In such parts of a flame metals, much less oxidisable than the alkali 

 metals, are rapidly oxidised when in the massive state. A copper vf.re, for example, 

 becomes incrusted with oxide in a region where yellow 'light is abundantly emitted 

 from a salted flame. A superoxygenated oxy-hydrogen flame is also coloured 

 yellow by salt. 



In discussing these facts* one of us was led to consider whether an alternative 

 explanation might not be sought from some conclusions, derived by Professor 

 AIMMIKNIUS, from a study of the electrical conductivity of salt vapours in flames.t 



Philosophic! Magazine ' (V.), vol. 37, 245, 1894. 

 t 'Wii-d. Ann.,' v.l. !_'. IS, 1891. 

 VOL. CXOIir. A, N 9.0.99 



