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In the manufacture of precipitated sulfur calcium pentasulfide (CaS5, main product) and calcium thiosulfate (CaS203, by-product) are decomposed simultaneously by hydrochloric acid into coarse (not being uniform) particle-size products. To improve this drawback, calcium thiosulfate was prepared directly without making calcium pentasulfide and obtained S6 by the acid-decomposition. In the conversion of hexatomic sulfur to octatomic sulfur, the polymerization and the depolymerization were observed by using purification method. The conversion of S6 to S8 is proceeded by two steps. The first step reaction is affected by impurities (especially S02 and H2S). Hexatomic sulfur is inert to triethylamine for the time being by purification, and thereafter a slow conversion to polymeric and then to octatomic sulfur occurs. Instead of calcium pentasulfide, the acid decomposition of calcium thiosulfate has several advantages; uniformity of particle-size of product, increase of yield, and simplicity of procedure.
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