Spectrum Chemical manufactures and distributes fine chemicals with quality you can count on including those with CAS number 573-58-0, Whether you call it Congo Red, Direct Red 28 or Disodium 3 -3-[Biphenyl-4 -4-diylbis(azo)]bis[4-aminonaphthalene-1-sulphonate] you can be assured the Congo Red products offered by Spectrum, meet or exceed the grade requirements or specifications for each individual product.