A method for producing methylene blue comprising: providing a reaction mixture comprising one or more methylene blue intermediates; reducing the metal content therein by precipitation during solvent extraction under basic conditions wherein the basic condition is between pH9 and pH 11; producing therefrom crude methylene blue; purifying crude methylene blue to obtain methylene blue having purity greater than 97%; wherein providing the reaction mixture comprises: reacting N,N-dimethylaniline with sodium nitrite in hydrochloric acid to obtain an in-situ nitroso compound; reducing the in-situ nitroso compound in the presence of zinc and hydrochloric acid to obtain in-situ p-amino dimethyl aniline; reacting the in-situ p-amino dimethyl aniline with sulfuric acid and zinc chloride in a presence of sodium thiosulfate pentahydrate, sodium dichromate, and aluminium sulphate octahydrate to obtain an in-situ thiosulfonic acid compound; treating the in-situ thiosulfonic acid compound with another molecule of N,N-dimethylaniline in a presence of sodium dichromate and zinc chloride to yield in-situ Di-cyclic compound; and allowing the in-situ Di-cyclic compound to undergo a cyclisation reaction in presence of manganese oxide to yield methylene blue crude; purifying the methylene blue crude in water and tetrahydrofuran, followed by treatment with hydrochloric acid to get methylene blue. providing a reaction mixture comprising one or more methylene blue intermediates; reducing the metal content therein by precipitation during solvent extraction under basic conditions wherein the basic condition is between pH9 and pH 11; producing therefrom crude methylene blue; purifying crude methylene blue to obtain methylene blue having purity greater than 97%; wherein providing the reaction mixture comprises: reacting N,N-dimethylaniline with sodium nitrite in hydrochloric acid to obtain an in-situ nitroso compound; reducing the in-situ nitroso compound in the presence of zinc and hydrochloric acid to obtain in-situ p-amino dimethyl aniline; reacting the in-situ p-amino dimethyl aniline with sulfuric acid and zinc chloride in a presence of sodium thiosulfate pentahydrate, sodium dichromate, and aluminium sulphate octahydrate to obtain an in-situ thiosulfonic acid compound; treating the in-situ thiosulfonic acid compound with another molecule of N,N-dimethylaniline in a presence of sodium dichromate and zinc chloride to yield in-situ Di-cyclic compound; and allowing the in-situ Di-cyclic compound to undergo a cyclisation reaction in presence of manganese oxide to yield methylene blue crude; purifying the methylene blue crude in water and tetrahydrofuran, followed by treatment with hydrochloric acid to get methylene blue. reacting N,N-dimethylaniline with sodium nitrite in hydrochloric acid to obtain an in-situ nitroso compound; reducing the in-situ nitroso compound in the presence of zinc and hydrochloric acid to obtain in-situ p-amino dimethyl aniline; reacting the in-situ p-amino dimethyl aniline with sulfuric acid and zinc chloride in a presence of sodium thiosulfate pentahydrate, sodium dichromate, and aluminium sulphate octahydrate to obtain an in-situ thiosulfonic acid compound; treating the in-situ thiosulfonic acid compound with another molecule of N,N-dimethylaniline in a presence of sodium dichromate and zinc chloride to yield in-situ Di-cyclic compound; and allowing the in-situ Di-cyclic compound to undergo a cyclisation reaction in presence of manganese oxide to yield methylene blue crude; purifying the methylene blue crude in water and tetrahydrofuran, followed by treatment with hydrochloric acid to get methylene blue. <EOS>