Azovan Blue
Evans blue(4-) is an organosulfonate oxoanion obtained by deprotonation of the four sulfo groups of 6,6'-{(3,3'-dimethyl[1,1'-biphenyl]-4,4'-diyl)bis[diazene-2,1-diyl]}bis(4-amino-5-hydroxynaphthalene-1,3-disulfonic acid). It is a conjugate base of an Evans blue free acid.