Naphthol yellow S is an organic compound with the formula . It is one of several isomers of sulfonated dinitro-1-naphthol. It is prepared by nitration of a trisulfonate of 1-naphthol, a process involving replacement of sulfonate groups with nitro. It is a derivative of 1-naphthol. At one time it was a popular food colorant but it was delisted in 1959 in the U.S.
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