The Hilton-davis Chemical Co.

Robert W Rebhahn

Raymond E Werner

James E Kassner

Wayne L Cook

The disodium salt of 1-[(6-methoxy-4-sulfo-3-methylphenyl)azo]-2-naphthol-6-sulfonic acid (FD and C Red 40), the disodium salt of 1-[(4-sulfophenyl)azo]-2-naphthol-6-sulfonic acid (FD and C Yellow 6), the trisodium salt of 1-[1-(4-sulfonaphthyl)azo]-2-naphthol-3,6-disulfonic acid (FD and C Red 2), the disodium salt of 2-[1-(4-sulfonaphthyl)azo]-1-naphthol-4-sulfonic acid (Carmoisine) and the sodium salt of 2-(2-quinolyl)-1,3-indanedione-sulfonic acid (D and C Yellow 10) are prepared and purified in high yield and in a high state of purity by subjecting their aqueous reaction mixtures to ultrafiltration through a membrane of such structure and under such conditions that the impurities are separated from the reaction mixtures, and the products are concentrated in high purity concentrates from which the products can be isolated directly by evaporation of the solvent.

Ultrafiltration process for purification of dyes useful in foodstuffs

This invention relates to improved processes for the manufacture of quinolinic acid run with a higher concentration of reactants in the initial step wherein quinoline is oxidized with hydrogen peroxide in an aqueous sulfuric acid solution in the presence of copper sulfate to prepare copper quinolinate, and in subsequent steps converting the copper quinolinate from the initial step to quinolinic acid by treating the copper salt with alkali to form the water soluble alkali salt form of quinolinic acid precipitating the copper as insoluble cupric oxide and thereafter treating the soluble alkali salt form with acid to obtain the quinolinic acid, the improvement whereby the reaction of the initial step is carried out in a thermally controllable and safe manner and the formation of by-products is minimized which comprises in the initial step adding separately either in portion-wise multiple and approximately equal portions or adding continuously and simultaneously over a period of time each of the following, the sulfuric acid, the quinoline and the hydrogen peroxide to an aqueous solution of the copper sulfate over such time intervals of sufficient length spaced between each group of portion-wise additions or at such a rate as to allow the hydrogen peroxide to react to maintain an unreacted hydrogen peroxide concentration in the reaction of between approximately three and approximately fifteen percent.

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Berkley, MA, United States of America

Robert W Rebhahn