PARTIAL MOLAR CHARACTERISTICS OF GLYCINE AND ALANINE IN AQUEOUS-SOLUTIONS AT HIGH-PRESSURES CALCULATED FROM ULTRASONIC VELOCITY DATA

We describe a method for evaluating the apparent molar thermodynamic c haracteristics of solutes using data derived from ultrasonic velocity measurements. Using this method, we have determined the apparent molar volumes, the apparent molar thermal expansibilities, the apparent mol ar heat capacities, and the apparent molar adiabatic and isothermal co mpressibilities of glycine and alanine in aqueous solutions over the p ressure and temperatures ranges of 1-1000 bar and 18-45-degrees-C, res pectively. We interpret the resulting data in terms of a temperature a nd pressure induced reduction in the hydration of the charged termini. Thus, at elevated temperatures and pressures, water in the bulk mediu m becomes more like water in the hydration shell of the charged groups .