Power law in properties of sulfur near the polymerization transition

Sound velocity and attenuation in liquid sulfur have been measured at temperatures from 80 °C in the super cooled state through the melting temperature ~about 120 °C! to 200 °C under saturated pressure. The measurements were performed with a pulsed phase sensitive technique at frequencies from 5 to 22 MHz. Accuracy of the sound velocity measurements was 0.1%. A distinct feature in sound velocity was found near 159 °C where sulfur experiences an equilibrium polymerization. However, neither dispersion in the sound velocity nor any appreciable change in sound attenuation was observed. Excess sound velocity ~with respect to the monomeric liquid! was extracted from the data and used to estimate the extent of polymerization as a function of the temperature. Both quantities exhibit a similar power law behavior with the exponent close to 0.77.