4,4'-(3H-2,1-Benzoxathiol-3-ylidene)bis(2,6-diiodophenol) S,S-dioxide 4430-24-4 EINECS 224-621-3 Iodophenol blue NSC 36792 Phenol, 4,4'-(3H-2,1-benzoxathiol-3-ylidene)bis(2,6-diiodo-, S,S-dioxide