342 
CHEMISTRY: KEYES AND WINNINGHOFF 
CHANGE OF THE IONIZATION OF SALTS IN ALCOHOLIC 
SOLVENTS WITH THE CONCENTRATION 
By Frederick G. Keyes and W. J. Winninghoff 
RESEARCH LABORATORY OF PHYSICAL CHEMISTRY. 
MASSACHUSETTS INSTITUTE OF TECHNOLOGY 
Received by the Academy, May 8, 1 91 6 
The deviation of largely ionized substances, even in fairly dilute so- 
lution, from the mass-action law, and in general from the behavior of 
perfect solutes, has been the subject of extended discussion among phy- 
sico-chemical investigators. Evidence is accumulating that at suf- 
ficiently small ion-concentrations these substances become normal in 
their behavior. Thus Kraus and Bray^ showed that uniunivalent salts 
dissolved in liquid ammonia and in certain organic solvents conform to 
the mass-action law when the concentration of the ions in the solution 
lies below about 0.0001 normal in ammonia, 0.0005 normal in organic 
solvents; and Arrhenius^ has made recalculations with the data of Kohl- 
rausch and Maltby on the conductance of aqueous solutions of sodium 
chloride and nitrate which indicate that these salts behave as perfect 
solutes in water at concentrations between 0.00002 and 0.0002 normal. 
A great variety of expressions have been proposed to account for the 
deviations at higher concentrations. Of these the one which is most 
generally applicable is that proposed by Kraus and discussed fully by 
Kraus and Bray.^ Kraus and Bray have shown that the conductance 
of almost any uniunivalent solute in any solvent from the concentra- 
tion zero up to a fairly high concentration (one where the change in the 
viscosity of the solution becomes an important factor) can be expressed 
by an equation of the form : 
In this equation K, D, and m are empirical constants which vary with 
the nature of the solute and of the solvent and with the temperature, 
and 7 represents the equivalent-conductance ratio A/An. This expres- 
sion evidently requires that any solute in any solvent conform to the 
mass-action law at sufficiently small concentrations, when the term 
D(cy)^ becomes negligible. 
The present investigation on the conductance of sodium iodide and 
ammonium iodide in isoamyl alcohol and of sodium iodide in propyl 
alcohol was undertaken for two purposes : primarily, in order to deter- 
mine whether in these solvents, somewhat similar in nature to water, 
