Norihiro Matubayasi

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. The variations in surface tension on mixing in the surface region are discussed using comparisons with mixtures of simple salts.

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. We also observed a decrease in the entropy change of surface formation with increasing concentration. The importance of an electrical double layer at the surface is discussed in relation to these surface tension increments.

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. It was shown that the surface activity of a salt largely dependent upon its valence type as well as its specific property of anion.