Acid Green 3

Guinee green B is an organic sodium salt having 3-[(ethyl{4-[(4-{ethyl[(3-sulfonatophenyl)methyl]amino}phenyl)(phenyl)methylidene]cyclohexa-2,5-dien-1-ylidene}azaniumyl)methyl]benzene-1-sulfonate. Used as a substitute for Light green SF yellowish in Masson's trichrome, although it is prone to fade. Previously used as a food dye but is now no longer approved. It has a role as a fluorochrome, a histological dye and a food colouring. It contains a Guinee green B(1-).