DESCRIPTION

Fast Green occurs as a red to brown-violet powder or granules. It is principally the inner disodium salt of N-ethyl-N-[4-[[4-[ethyl[(3-sulfophenyl)methyl]amino] phenyl](4-hydroxy-2-sulfophenyl)methylene]-2,5-cyclohexadien-1-ylidene]-3-sulfobenzene-methanaminium hydroxide. It dissolves in water to give a solution blue-green at neutrality, green in acid, and blue-violet in base. When dissolved in sulfuric acid, it yields a brown-orange solution that turns green when diluted with water. When heated to 130° with triacetin and an excess of acetic anhydride, acetylation of its phenolic hydroxyl group causes a color change from green to light blue. It is slightly soluble in ethanol.