The reaction flask containing 100 g. H2S2 is cooled with Dry Ice-methanol to -60 to -65℃ in a Dewar flask. From the separatory funnel, 10 g of SCl2 (about 0.1 mole) is allowed to drip in slowly (with stirring) in such a way that the temperature of the mixture does not rise above -55℃. In contrast to the preparation of tetrasulfane, the use of a bent outlet capillary is not recommended, since it plugs easily. The Dewar flask is removed 15 minutes after the completion of the dropwise addition. When the mixture has warmed to 0℃, the temperature is held constant until the evolution of HCl has, for all practical purposes, ended; the mixture is then stirred for another 0.5 hour at room temperature. The total reaction time is 1.5 hours.
