VOLUMES AND HEAT-CAPACITIES OF H3BO3(AQ) AT TEMPERATURES FROM 298.15 K TO 705 K AND AT PRESSURES TO 35 MPA

The densities and heat capacities of aqueous solutions of boric acid h ave been measured at temperatures from 298.15 K to 705 K and at pressu res up to 35 MPa. The results are in reasonable agreement with the pre vious measurements at temperatures of 600 K and below. At temperatures and pressures in the neighborhood of the critical point of water, the results show the expected dependence of partial molar volume and part ial molar heat capacity of H3BO3(aq) on temperature and density. The b oric acid molecules have strong enough attractive interactions with wa ter that the apparent molar volume and the apparent molar heat capacit y of H3BO3(aq) show behavior with the same sign as of aqueous NaCl, al though the magnitude is much less. (C) 1995 Academic Press Limited