THERMODYNAMIC PROPERTIES OF POLYMERIC SULFUR S(OMEGA-2) AT TEMPERATURES BETWEEN 5-K AND 370-K

The molar heat capacity of polymeric sulfur Sω2 has been determined at temperatures T between 5 K and 370 K. Values of the derived thermodynamic functions are tabulated to T = 300 K. Above T = 310 K a gradual transition to a more stable form of sulfur occurs. From the total enthalpy increase between T = 310 K and T = 370 K we estimate that ΔfHom(Sω2) ≥ 666 J·mol-1. The entropy increment Δ298.15 K0Som(Sω2) = 32.84 J·K-1·mol-1. A comparison of the heat capacities of the three known crystal forms of sulfur is made and standard Gibbs free energies of formation are calculated. The deduced enthalpy of transition between S(orthorhombic) and Sω2 compares well with the mass-spectrometric values measured independently. © 1993 Academic Press Ltd.