Apparent Molar Volumes and Viscosities of Dl-α-Alanine in Water-Ethanol Mixtures

Abstract

In this work we present a systematic study of the apparent molar volumes and the viscosities of DL-α-alanine in aqueous ethanol solutions at 25,00°C. The molar fractions of ethanol for the solvent mixtures were selected taking into account that thermodynamic properties such as partial molar volumes and heat capacities of these mixtures show a transition concentration around X _et = 0,1 at which its behavior suffers a deep change. Besides, this ethanol concentration is near to that required to produce 50% of protein denaturation.

The results were used to evaluate the limiting partial molar volume V0 of the solute the volume changes associated with its transfer from water to aqueous ethanol solutions and the viscosity B coefficients of DL-α-alanine. The values obtained for the transference molar volumes and the viscosity B coefficients of alanine in the aqueous mixtures show a minimum at X _et = 0,1000. The results are discussed in terms of changes in the solvent structure (Ref. [1])

Key Words:

• Amino acid
• apparent molar volume
• viscosity
• mixed solvents
• solute-solvent interactions