16574-43-9 Bromopyrogallol red NSC315537 Pyrogallol bromine red Spiro[3H-2,1-benzoxathiole-3,9'-[9H]xanthene]-3',4',5',6'-tetrol, 2',7'-dibromo-, 1,1-dioxide Spiro[3H-2,1-benzoxathiole-3,9'-xanthene]-3',4',5',6'-tetrol, 2',7'-dibromo-, 1,1-dioxide