APPARENT MOLAR HEAT CAPACITIES OF AQUEOUS SOLUTIONS OF PHOSPHORIC ACID AND SULFUR DIOXIDE FROM 303 TO 623 K AND A PRESSURE OF 28 MPA

摘要

Heat capacities of aqueous solutions of phosphoric acid from 0.1 to 0.8 mol-kg(-1) and sulfur dioxide from 0.2 to 0.9 mol-kg(-1) have been measured with a flow heat-capacity calorimeter from 303 to 623 K and a pressure of 28 MPa. At the lowest molality single-solute solutions as well as mixtures of either H3PO4 or SO2 with HCl were measured to repress dissociation. Calculated apparent molar heat capacities were corrected for dissociation reactions and the chemical relaxation effect. Experimental results for mixtures were analyzed using Young's rule. Standard state partial molar heat capacities of H3PO4(aq) and SO2(aq) were obtained by extrapolation to infinite dilution. A few measurements of the densities of aqueous H3PO4 and SO2 were made at 25 degrees C and a pressure of 28 MPa. [References: 26]