The Partial Molal Volumes and Compressibilities of Nonelectrolytes and Amino Acids in 0.725 m NaCl

Abstract

The partial molal volumes and compressibilities of a number of nonelectrolytes and amino acids in 0.725 m NaCl have been determined from density and compressibility measurements. The results have been used to examine the behavior of these compounds in ocean waters. The partial molal volumes of the solutes in 0.725 m NaCl were a linear function of the values in water. The partial molal compressibilities of urea, sugars and amino acids were all negative due to the hydration of water molecules. The values of partial molal compressibilities in 0.725 m NaCl were not as negative due to the decrease in the hydration in the salt solution. A simple hydration model is used to estimate the number of water molecules hydrated to the solutes in 0.725 m NaCl. The partial molal volumes and compressibilities for the nonelectrolytes determined in this study should be useful in estimating the effect of pressure on equilibrium reactions of these compounds in seawater.