Viscosity <i>B</i> Coefficients for Some Homologous Series of Organic Electrolytes in Aqueons Solutions. The Effect of Ionic Groups

Abstract

Abstract The viscosity B coefficients for the three homologous series of sodium alkane carboxylates (acetate to butyrate), sodium n-alkyl sulfonates (methyl to hexyl), and n-alkylammonium chlorides (methyl to hexyl) in aqueous solutions at 25 °C have been determined. The B values increase linearly with the number of carbon atoms in the alkyl chains for each homologous series studied in this work, as well as for a homologous series of n-alkyl sulfate ions previously studied. In the case of the three kinds of organic anions with the same alkyl groups, the B values increase in the order: –COO−&amp;gt;&amp;gt;–SO3−&amp;gt;–OSO3−. The ion-solvent interaction effect, as estimated by the combination of the B values with the molal volume at an infinite dilution for ions, is positive for each carboxylate ion; however, it is negative for the lower alkyl sulfonate, alkyl sulfate and alkylammonium ions. From these facts, –COO− may be classified as an “electrostrictive structure-maker,” whereas, –SO3−, –OSO3−, and –NH3+ are “electrostrictive structure-breakers.” In this connection, the reported specific interactions of these ionic parts with simple counter-ions on the activity coefficients of organic electrolytes, the counter-ion binding of polyelectrolytes, and the effect of counter-ions on the critical micelle concentrations of long-chain electrolytes are briefly discussed on the basis of the change in water structure induced by both cations and anions in water.