The Molecular Composition of Hydrophilic Sulfur Sols Prepared by Acid Decomposition of Thiosulfate [1]

Hydrophilic sulfur sols prepared from sodium thiosulfate and concentrated sulfuric acid and purified by repeated NaCl precipitation and peptization in water have been studied by chemical analysis, vibrational spectroscopy, ion-pair chromatography and reversed-phase HPLC. The composition of the sol is Na₁.₆₄S₂₈.₆O₆ · 5.9/n Sₙ · 1.0 NaCl. The elemental sulfur Sₙ (n = 6-14; mainly S ₈) accounts for 17% the total sulfur; 83% of the S are present as long-chain polythionates which form micelles in which the Sₙ molecules are dissolved. On aging of the sol at 20 °C the polythionate micelles decompose to give water-soluble short-chain polythionates and elemental sulfur which precipitates from the solution. The micelle structure of hydrophilic sulfur sols may serve as a model for the so-called sulfur globules (S°) formed intra- or extracellularly by many sulfur bacteria which oxidize reduced sulfur compounds to S°. - ᴛ∙nfrared and Raman spectra of K₂SₘO₆ (m = 3-6) are reported. The photodecomposition of aqueous tetrathionate yields sulfite, thiosulfate, and polythionates with up to 9 sulfur atoms