Syonyms Name: D & C Red no. 21; 2',4',5',7'-Tetrabromo-3',6'-dihydroxyspiro(isobenzofuran-1(3H),9- '-(9H)xanthen)-3-one; 2',4',5',7'-Tetrabromofluorescein; Spiro(isobenzofuran-1(3H),9'-(9H)xanthen)-3-one, 2',4',5',7'-tetrabromo-3',6'-dihydroxy-; 3,6-Dihydroxy-2,4,5,7-t