Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

The surface tension of glycine, alanine, 2-aminobutyric acid (AABA), norvaline and norleucine in water and in aqueous solutions of five strong electrolytes (LiCl, NaCl, KCl, (NH4)2SO4 and Na2SO4) was determined in the temperature range between 293.15 and 313.15 K with a tensiometer LAUDA TVT2 using the drop volume method. As temperature rises, surface tension decreases as cohesion between molecules becomes lower. The limiting slopes of the surface tension as a function of mole fraction of the amino acids in water show that glycine and alanine are hydrophilic solutes, while a-aminobutyric acid, norvaline and norleucine behave as hydrophobic solutes and this behavior is not affected by the addition of the salts. The presence of electrolytes increases the surface tension of the a-amino acid solutions, however, it is not possible to classify the effect of the anions and cations on this property since the surfaces of the mixed solvents are different and a comparison between them is not pertinent.