Hexaatomic Sulfur

NajSjO. + 2HC1 [H2S2O,] +2NaCl eiHsSgO,] - Se + 6SO2 + 6H2O 

Submitted by Paul D. Bartlett and William R. RoDERicst Checked by William C. Andersen  

Hexaatomic sulfur, first isolated in 1891, has been prepared only by the acidification of aqueous solutions of thiosulfates.The unstable thio ulfuric acid so generated decomposes to numerous products depending on the concentrations of the reactants and on the temperature. Anhydrous solutions of thiosulfuric acid in ether are stable at —78° at 25° they decompose to hydrogen sulfide and sulfur trioxide. There is evidence for the presence of Se in the gas phase of sulfur.  

The yield of S is low, being about 4% following the original procedures - and about 12 to 15% with the procedure described herein. The yield of Se has been found to be maximal when the extraction is carried out as the reaction mixture warms to room temperature later extraction gives less Se. The yield of S is about the same when acidification occurs at 0°, but the extract appears to contain more Ss than is obtained at —15°. 

Two hundred milliliters (2.4 mols) of 12 N hydrochloric acid is placed in a 500-ml. three-necked round-bottomed flask fitted with a dropping funnel containing 50 ml. (approximately 0.2 mol) of saturated aqueous sodium thiosulfate (prepared and used at room temperature), an all- 

NajSjO, + 2HCl- [HjSjO,] +2NaCl OlHjSsOs] — Sg i 6SOj -f 6HiO 

Submitted bt Paul D. Bartlstt and Wiujam R. RoDERicKf Checked bt William C. Andersen  

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For purification, the crystalline hexaatomic sulfur is dissolved in benzene (approx. 100 mg./l.) toluene is not suitable (see Properties). The benzene solution is extracted with a series of reagents, three or four extractions being made with each reagent except where otherwise indicated. (For 200 ml. of benzene solution, 50-ml. portions of reagent are used). The reagents are employed in the following order (1) water, (2) 10% aqueous potassium triiodide, until the benzene phase remains colored from iodine, (3) 10% aqueous potassium iodide, (4) water, (5) 5% aqueous lead acetate, twice, (6) water, (7) 5 % aqueous potassium hydroxide, once, (8) water. The purified solution is dried over magnesium sulfate and should be used immediately. The approximate concentration of Sg can be determined spectro-photometrically at 300 mju (e = 181 l./g.-atom) after suit-... 

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