[2] It is used to color nonpolar substances such as oils, fats, waxes, greases, various hydrocarbon products, and acrylic emulsions.
Its main use is as a fuel dye in the United States mandated by the Internal Revenue Service (IRS) to distinguish low-taxed heating oil from automotive diesel fuel, and by the United States Environmental Protection Agency (EPA) to mark fuels with higher sulfur content; it is a replacement for Solvent Red 26 with better solubility in hydrocarbons.
[3] The IRS requires "a concentration spectrally equivalent to at least 3.9 pounds of... Solvent Red 26 per thousand barrels of fuel" (11.1 mg/L);[4] the concentrations required by EPA are roughly 5 times lower.
It has the appearance of reddish brown crystals and a maximum absorption at 507(304) nm.
In botany, it is used with Light Green SF Yellowish to differentiate between suberized and cutinized plant tissue.