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

The behaviors of a series of calcium halides and of alkali earth metal chlorides in the air/water surface region were studied in comparison with those of alkali metal halides by measuring the surface tension increments of solutions. The effect of salts with divalent cations on the surface tension increments is more pronounced than that of uni-univalent salts, but there are some similarities between these two types. It seems that the anions cause a marked effect on surface tension which is proportional to the magnitude of hydration in the bulk water.

Thermodynamic quantities of surface formation of aqueous electrolyte solutions: IX. Aqueous solutions of ammonium salts.

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.

Thermodynamic quantities of surface formation of aqueous electrolyte solutions VIII. Aqueous solutions of sulfates salts.

In this work the surface tension of the aqueous solutions of alkali metal sulfate, magnesium sulfate, and magnesium nitrate have been measured with an expectation that the effect of sulfate salts on the air/water surface differs from that of typical electrolyte because of their peculiar results of surface potential data. The results show that the slope of surface tension-concentration curves of sulfate salts depends to some extent upon cations while that of alkali metal nitrate gives almost the same magnitude. In order to make comparison with salts of different valence types, we used the ratio of surface excess density to bulk concentration of a salt as an index of surface activity of the salt.

Thermodynamic quantities of surface formation of aqueous electrolyte solutions VII. Aqueous solution of alkali metal nitrates LiNO3, NaNO3, and KNO3.

To compare the effect of nitrate anions on the surface tension increments of aqueous solutions with that of halide anions, the surface tension of aqueous solutions of lithium nitrate, sodium nitrate, and potassium nitrate was measured as a function of temperature and concentration. It is shown that the surface tension of aqueous alkali metal nitrate solutions is determined primarily by the kinds of anions, since the surface tension increments of these nitrates were of the same magnitude. The importance of the electrical double layer at the surface is discussed in relation to these surface tension increments.

Thermodynamic quantities of surface formation of aqueous electrolyte solutions. VI. Comparison with typical nonelectrolytes, sucrose and glucose.

To demonstrate an important distinction between the electrolytes and nonelectrolytes, surface tension of aqueous solutions of typical nonelectrolytes, sucrose and glucose, was measured as a function of temperature and concentration. The presence of sucrose or glucose molecules in the surface region affects the surface tension in the same way as the presence of an ion does. There is, however, a difference in the temperature coefficient of the surface tension between typical nonelectrolyte solutions, sucrose and glucose, and alkali halide solutions.

Thermodynamic quantities of surface formation of aqueous electrolyte solutions. V. Aqueous solutions of aliphatic amino acids.

The surface tension of aqueous solutions of glycine, L-alanine, L-valine, and L-leucine has been observed using the drop volume method as a function of temperature and concentration. The L-leucine molecules form an adsorbed film, while glycine affects the water surface in accordance with simple salts which dissociate into cations and anions completely. The surface tension data have been analyzed in view of K.

Surface properties of aqueous amino acid solutions II. Leucine-leucine hydrochloride and leucine-sodium leucinate mixtures.

To understand the distinction between the effects of zwitterionic, anionic, and cationic l-leucine upon adsorption and lateral interactions at air/water surface, the surface tensions of aqueous solutions of l-leucine-l-leucine hydrochloride and l-leucine-sodium l-leucinate mixtures were measured as a function of concentration and composition at 25 degrees C. The surface activity decreases in the order l-leucine >l-leucine hydrochloride > sodium l-leucinate. Both l-leucine hydrochloride and sodium l-leucinate form gaseous adsorbed films through the experimentally accessible concentration range, while the adsorbed film of zwitterionic l-leucine shows a transition between gaseous and expanded film.

Surface properties of aqueous amino acid solutions. I. Surface tension of hydrochloric acid-glycine and glycine-sodium hydroxide systems.

The surface tensions of aqueous solutions of four mixtures (hydrochloric acid-glycine hydrochloride, glycine hydrochloride-glycine, glycine-sodium glycinate, and sodium glycinate-sodium hydroxide) were measured as a function of total molality and mole fraction. The measurements correspond to the change in surface tension with variation of pH. The contribution of glycine hydrochloride to the increments in surface tension is equivalent to that observed for the aqueous solution of glycine, while the contribution of sodium glycinate is much larger than that of glycine.