A Helmholtz Energy Equation of State for Sulfur Dioxide

A Helmholtz energy equation of state with independent variables of temperature and density was developed for sulfur dioxide (SO2) based on thermodynamic property data from the literature. The equation of state is valid from the triple-point temperature of 197.7 to 525 K, with pressures up to 35 MPa and densities up to 25.4 mol.dm(-3). The uncertainties in density of the equation of state are 0.1% in the liquid phase, 0.25% in the vapor phase, and 1% in the critical region. The uncertainty in vapor pressure is 0.2% and the uncertainty in saturated liquid density is 0.2% below 410 K. The uncertainty in isobaric heat capacity is 2% between 200 and 290 K. In the critical region, the uncertainties are higher for all properties except for vapor pressure. The behavior of the equation of state is correct not only within the region of validity, but also at high temperatures and pressures, and far below the triple-point temperature.