Oil Blue 35

Oil Blue 35, also called Solvent Blue 35, Blue 2N, Blue B, Oil Blue B, 1,4-bis(butylamino) anthraquinone and CI 61554, is a blue dye derived from anthraquinone. It has the appearance of a dark bluish-black powder, soluble in benzene and toluene and insoluble in water, with melting point 104-105 °C. When exposed to 5% hydrochloric acid solution, it becomes dirty green.

Sudan Blue II is used as a dye for alcoholic, ester, and hydrocarbon based solvents, oils, fats, and waxes. It is used also in lacquers and inks. In some countries, it is used as a fuel dye. It is also used in some blue colored smoke formulations. In microscopy, it is used as a staining dye.

A chemically similar dye is Solvent Blue 36.