Molal volume of aqueous boric acid-sodium chloride solutions

The apparent molal volume φ _v of boric acid has been determined in various sodium chloride solutions at 0 and 25°C from precise density measurements. Similar to its behavior in pure water, the φ _v of boric acid in NaCl solutions is a linear function of the concentration. The infinite dilution φ _v ^° and the slope S _v ^* of B(OH)₃ are larger in NaCl solutions than in pure water. NaCl appears to be able to dehydrate B(OH)₃ and cause an increase in B(OH)₃-B(OH)₃ interactions. The mean apparent molal volumes Φ _v of the B(OH)₃−NaCl solutions are predicted from pure water data using a modification of Young's rule for electrolyte-nonelectrolyte mixtures and are compared to the directly measured values. A similar treatment was carried out on the density data of acetic acid-sodium chloride solutions. The modified Young's rule was found to give a good first approximation of the mean apparent molal volumes of nonelectrolyte-electrolyte systems. The deviations from the Young's rule approximation are studied as excess volumes of mixing boric acid and NaCl solutions. Taken from a thesis submitted by Gary K. Ward in partial fulfillment of the requirements of the Master of Science degree, University of Miami, Miami, Florida 33149. Scientific Contribution Number 1731 from the University of Miami, Rosenstiel School of Marine and Atmospheric Science, Miami, Florida 33149.