Abstract: The process for recovering recyclable sulphur from a strongly colored solution obtained from the production of sulphur dyestuffs containing alkali metal sulfides, alkali metal polysulfides, sulphur dyestuffs or mixtures thereof comprising(a) mixing said solution at an alkaline pH with a decolorizing amount of an iron or zinc compound which is a hydroxide or the salt of an inorganic acid whereby a precipitate is formed,(b) separating the precipitate to isolate a decolorized solution, and either(c) precipitating elemental sulphur from the decolorized solution by adding sulphur dioxide or alkali metal thiosulfate under acidic conditions, and(d) separating the precipitated elemental sulphur, or(e) recycling the decolorized solution for use in the manufacture of sulphur dyestuffs.

Abstract: In the processs for isolating solid sulphur dyestuffs from crude sulphur dyestuff melts, the improvement comprises adding 10.sup.-4 to 1% by weight, relative to the amount of dyestuff, of an organic flocculating auxiliary to the crude dyestuff melt to produce a filterable dyestuff precipitate and then separating said precipitate.

Abstract: The process for recovering recyclable elemental sulfur from a strongly colored solution containing alkali metal sulfides, alkali metal polysulfides, or mixtures thereof comprising(a) mixing said solution at an alkaline pH with a decolorizing amount of an iron or zinc compound which is a hydroxide or the salt of an inorganic acid whereby a precipitate is formed,(b) separating the precipitate to isolate a decolorized solution,(c) precipitating elemental sulfur from the decolorized solution by adding sulfur dioxide or alkali metal thiosulfate under acidic conditions, and(d) separating the precipitated elemental sulfur.