Solubility of cyclooctasulfur in pure water and sea water at different temperatures

The solubility of cyclooctasulfur in water and sea water at various temperatures in the range between 4 and 80 degrees C was determined. Cyclooctasulfur in equilibrium with rhombic sulfur reacted with hot acidic aqueous potassium cyanide to form thiocyanate anion which was measured by anion chromatography. Sulfur solubility in pure water was found to increase with temperature by more than 78 times: from 6.1 nM S-8 at 4 degrees C to 478 nM S-8 at 80 degrees C. The following thermodynamic values for solubilisation of S8 in water were calculated from the experimental data: K degrees = 3.01 +/- 1.04 x 10(-8), Delta G(r)degrees = 42.93 +/- 0.73 kJ mol(-1), Delta H-r degrees = 47.4 +/- 3.6 kJmol(-1), Delta S-r degrees = 15.0 +/- 11.7 J mol(-1) K-1). Solubility of cyclooctasulfur in sea water was found to be 61 +/- 13% of the solubility in pure water regardless of the temperature. (C) 2009 Elsevier Ltd. All rights reserved.