Sudan III

Uses

It is used to color nonpolar calamaro substances like oils, fats, waxes, greases, various hydrocarbon products, and acrylic emulsions. Its main use is as a fuel dye in the United States of America mandated by the IRS to distinguish low-taxed heating oil from automotive diesel fuel, and by the EPA to mark fuels with higher sulfur content; it is a replacement for Solvent Red 26 with better solubility in hydrocarbons. The concentration required by IRS is a spectral equivalent of 3.9 pounds per 1000 barrels, or 11.13 mg/l, of Solvent Red 26 in solid form; the concentrations required by EPA are roughly 5 times lower.

It is also used to dye some hydraulic fluids and some other hydrocarbons, predominantly gasoline.

Biological staining

Sudan III is a dye used for Sudan staining. Similar dyes include Oil Red O, Sudan IV, and Sudan Black B. They are used for staining of triglycerides in frozen sections, and some protein bound lipids and lipoproteins on paraffin sections. It has the appearance of reddish brown crystals and a maximum absorption at 507(304) nm.

Its other names are Sudan Red BK, Fat Ponceau G, Cerasin Red, C.I. 26100, Solvent Red 23, Sudan Red, Sudan Red III, Sudan V, Sudan Red B, Sudan G, Scarlet B, and Tony Red.

Safety

Sudan I, Sudan III, and Sudan IV have been classified as category 3 carcinogens by the International Agency for Research on Cancer.

Its risk and safety phrases are S22-S24/S25.