Solvent Red 26
Benzidine Yellow 10G, Sanyo Pigment Yellow 8105
|Molar mass||394.48 g·mol−1|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Solvent Red 26, also known as C.I. 26120, is a purplish red synthetic azo dye. It is soluble in oils and insoluble in water.
Its main use is as a standard fuel dye in the US mandated by the US IRS to distinguish low-taxed or tax exempt heating oil from automotive diesel fuel, and by the EPA to mark fuels with higher sulfur content; it is however increasingly replaced with Solvent Red 164, a similar dye with longer alkyl chains, which is better soluble 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.