Cachou de Laval: This was the first sulfur dye. It is obtained by heating brown coal in a rotary baker with sodium polusulfide and sulfur. It is also made by heating organic refuse with sulfur and sodium sulfide at temoeratures varying from 100⁰-350⁰C. The higher the temperature, the darker the product. Other alternatives intermediates are lignite, sawdust, bran, sulfite cellulose waste liquors (free from calcium), oils, fats and fatty acids. It appears as black hygroscopic lumps or powder. It is readily soluble in water with greenish black or brown colour but is rendered insoluble by prolonged boiling. Other brown dyes: Brown sulfur dyes are made from natural biomass10 i.e the residual product which is obtained from the usual human crop
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Sulfur Brown 4,5,14,53,62. Sulfur Brown 14 is obtained by heating o- or p-(2,4-dinitroanilino)phenol with caustic soda and water to 105⁰C and then add dextrose, sodium sulfide and sulfur. Sulfurization temperature may vary from 123⁰C (under reflux) to 160⁰C (bake).
Dyes from substituted naphthalenes:
Brown dyes of this type include C.I. Sulfur Brown 7,15,16,31,63. Sulfur Brown 15 is obtained by Obtained by baking a mixture of 138 parts of 1,5-dinitronaphthalene and 75 parts of crude cresol with sodium polysulfide, in the presence of copper sulfate and sodium chloride at 265⁰C for 12-14 hours. The 1,5-dinitronaphthelene may be reduced at 95⁰C with sodium polysulfide before baking.
Dyes from polycyclic compounds: Brown dyes of this type include C.I. Sulfur Brown 6,51,52,60. Sulfur Brown 52 is obtained by by baking a mixture of decacyclene and sulfur at temperatures up to 350⁰C during 20 hours and maintaining at this temperature for a further 8 hours. The product is treated in caustic soda at 100-110⁰C, filtered and precipitated. This dye possesses exceptionally good fastness to
Sulfur Brown 4,5,14,53,62. Sulfur Brown 14 is obtained by heating o- or p-(2,4-dinitroanilino)phenol with caustic soda and water to 105⁰C and then add dextrose, sodium sulfide and sulfur. Sulfurization temperature may vary from 123⁰C (under reflux) to 160⁰C (bake).
Dyes from substituted naphthalenes:
Brown dyes of this type include C.I. Sulfur Brown 7,15,16,31,63. Sulfur Brown 15 is obtained by Obtained by baking a mixture of 138 parts of 1,5-dinitronaphthalene and 75 parts of crude cresol with sodium polysulfide, in the presence of copper sulfate and sodium chloride at 265⁰C for 12-14 hours. The 1,5-dinitronaphthelene may be reduced at 95⁰C with sodium polysulfide before baking.
Dyes from polycyclic compounds: Brown dyes of this type include C.I. Sulfur Brown 6,51,52,60. Sulfur Brown 52 is obtained by by baking a mixture of decacyclene and sulfur at temperatures up to 350⁰C during 20 hours and maintaining at this temperature for a further 8 hours. The product is treated in caustic soda at 100-110⁰C, filtered and precipitated. This dye possesses exceptionally good fastness to