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

ABSTRACT

The molal solubilities, density, and refractive index of the basic amino acid (l-lysine) and the neutral amino acid (l-cysteine) in aqueous solutions of potassium iodide (KI), sodium bromide (NaBr), sodium chloride (NaCl), sodium sulfate (Na2SO4), and calcium chloride (CaCl2) at 298.15 K were determined experimentally. From the values of the measured refractive indices, molal solubilities, and the densities, the excess refractive indices, the molar refractions, the polarizabilities, and the apparent molar volumes of the systems under study were calculated and discussed. The solvation of the amino acids under study was discussed in terms of their molal solubilities, apparent molar volume, and refractive index data. The phase diagrams of the studied tricomponent systems (water salt amino acid) were also determined and discussed. The solubility of l-cysteine and l-lysine were discussed in terms of the nature of the electrolytic salts under study. The effect of the electrolytic solutions under study on the solubility of l-cysteine and l-lysine was compared to that found in the literature of the same electrolytic solutions on the amino acids (dl-valine, dl-serine, glycine, and dl-alanine) at the same temperature. A salting-in effect of the electrolytic solutions under study (potassium iodide, sodium chloride, sodium bromide, calcium chloride, and sodium sulfate) and other electrolytic solutions (potassium fluoride, potassium bromide, sodium iodide, potassium sulfate, and barium chloride) (from literature) was observed for l-cysteine amino acid (present study), dl-valine, dl-serine, glycine, and dl-alanine (from literature) A salting-out effect of the electrolytic solutions under study (potassium iodide, sodium bromide, sodium chloride, sodium sulfate, and calcium chloride) was observed for l-lysine amino acid (present study), and of NaF solution for amino acids; dl-alanine and dl-valine (from literature). The effect of the nature of the electrolytic salts under study agree with that in the literature as in the following order: Na2SO4 greater than NaCl, NaBr greater than NaCl, CaCl2 greater than NaCl.