7-(diethylamino)-3-(1,3-dimethylbenzimidazol-3-ium-2-yl)chromen-2-one; methyl sulfate

Basic Yellow 40 is a fluorescent dye that exists as a salt form of a coumarin derivative containing a diethylamino group and a benzimidazolium moiety. It is primarily used for applications requiring fluorescent properties.