Surface Tension of Glycine, Alanine, Aminobutyric Acid, Norvaline, and Norleucine in Water and in Aqueous Solutions of Strong Electrolytes at Temperatures from (293.15 to 313.15) K

The surfacs tension of glycine, alanine, 2-aminobutyric acid (AABA), norvaline, arid norleucine in water and in. aqueous solutions of five strong electrolytes (LiCl, NaCl KCl, (NH4)(2)SO4, and Na2SO4) was determined in the temperature range between 293.15 and 313.15 K with a LAUDATVT2 tensiometer using, the drop volume method. As the temperature rises, the surface tension decreases as the cohesion between molecules becomes weaker. 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 whereas alpha-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 alpha-amino acid solutions; however, it is not possible to classify the effect of the anions, and-cations on this property because the surfaces of the mixed solvents are different and a comparison between them is not pertinent.