The thermodynamics of seawater at one atmosphere

The solution thermodynamic properties of seawater at 1 atm have been examined over the range of 0/sup 0/ to 40/sup 0/C and 0 to 40% salinity. By combining the osmotic coefficients (phi = -(55.51/2m) ln a/sub 1/, where m is the molality and a/sub 1/ is the activity of water) determined from the freezing point measurements of Doherty and Kester (1974), with the heat capacity data of Millero, Perron, and Desnoyers (1973), and the enthalpy data of Millero, Hansen, and Hoff (1973), the osmotic coefficients were determined over the range of 0/sup 0/ to 40/sup 0/C at 1 atm using the extended Debye-Heuckel equation. The results at 25/sup 0/C were found to be in excellent agreement with the results of Robinson (1954). From the osmotic coefficient data, the vapor pressure and osmotic pressure have been determined. The osmotic coefficient data at 0/sup 0/C has been used to calculate the mean activity coefficient and activity of ''sea salt.'' By using the thermodynamic equation delta lna/sub 2//delta T + - anti L/sub 2//RT, activities have been determined at other temperatures (0/sup 0/ to 40/sup 0/C). The relative free energies of seawater, G - G/sup 0/ + 55.51 RT ln a/sub 1/ =more » m RT ln a/sub 2/, have been calculated from the osmotic and activity data.The relative entropy of seawater (S - S/sup 0/) was determined from the relative free energies by using the thermodynamic relationship, S - S/sup 0/ + ((G - G/sup 0/) - (H - H/sup 0/))/T, where H - H/sup 0/ is the relative enthalpy. All the specific thermochemical properties (P) of seawater have been fitted to equations.« less