Methylene Blue cation
3,7-bis(dimethylamino)phenothiazin-5-ium is an organic cation that is phenothiazin-5-ium substituted by dimethylamino groups at positions 3 and 7. The chloride salt is the histological dye 'methylene blue'. It is a conjugate acid of a 3,7-bis(dimethylamino)phenothiazine.