Thermodynamic quantities of surface formation of aqueous electrolyte solutions

Abstract

The properties of aqueous ammonium salt solutions at the air/water surface are presented. By comparison of the properties of ammonium halides solutions with those of sodium halide, we note a close similarity, which indicates that the increments in surface tension may be explained in relation to the hydration enthalpy of anions. We find that the behaviors of the salts with nitrate anions which are polyatomic are also explained by hydration enthalpy in the same way. On the other hand, salts with ammonium cations which are polyatomic show deviation from a monotonous relationship between the surface tension increments and the hydration enthalpies observed for alkali metal halides. These results can be explained by ion pair formation in the surface region.

Thermodynamic quantities of surface formation of aqueous electrolyte solutions X. Aqueous solution of 2:1 valence-type salts

“…Water was doubly distilled from dilute alkaline permanganate solution. Surface tension was measured by the drop volume method which has proved useful through this series of measurements on the electrolyte solutions [7]. Measurements were made using glass dropping tips.…”

“…Fortunately, numerical values of this ratio at infinite dilution can be used to evaluate the Previously reported surface tension data used in this figure are taken from the references sodium halides [11,12], sulfates [14], nitrates [17], and ammonium salts [7], respectively. The formation of electrical double layer in the surface region is always accompanied by the decrease in s [18].…”

“…In the last paper of this series, we have reported the experimental results of the effect of ammonium cations on the surface tension of solutions and emphasized the interactions between anions and cations in the electrical double layer [7]. This will inevitably lead to an increment of surface tension even though the concentration of ions in the surface region is limited.…”