234 Proceedings of Royal Society of Edinburgh. [sess. 
Preliminary Note on the Conductivity of Concentrated 
Aqueous Solutions of Electrolytes. By Prof. J. Gibson. 
(MS. received October 12, 1905. Read November 6, 1905.) 
In a paper communicated to the Society in 1897, the author 
drew attention to increase in electrical conductivity as a 
characteristic of photo-chemical action, and in a second com- 
munication in December of the same year, made the following 
statement — 
“It would appear that the chemical behaviour of the acids just 
mentioned (HN0 3 , HC1, H 2 S0 4 ) depends in many of their reactions 
on whether their concentration is above or below that correspond- 
ing to their maximum electrolytic conductivity.” * 
As a result of prolonged investigation by the author, much 
experimental evidence tending in this direction has been gained, 
but the endeavour to arrive at a clear and definite physical meaning 
has been so far unsuccessful. It is very remarkable that during 
the last twenty years relatively little progress has been made in 
our knowledge of concentrated solutions. This is primarily due 
to the fact that hitherto no simple and general relationship has 
been discovered between the conductivity and the concentration 
of concentrated solutions of electrolytes. Oswald’s law of dilution 
holds only for dilute solutions of weak electrolytes, and the 
formulae of Rudolphi and of Yan T. Hoff are applicable only to 
dilute solutions of good electrolytes. 
Since the publication by Kohlrausch of his classical investiga- 
tions it has been customary, in stating the relationship between the 
conductivity and the concentration of solutions of electrolytes, to 
express the concentration as equivalent concentration, that is, in 
gram equivalents per unit volume of solution. It has also been 
customary to express the conductivity as equivalent conductivity, 
that is, as the ratio of the specific conductivity to the equivalent 
concentration. 
= specific conductivity. 
