Sulfan Blue

CI 42045; patent blue VF; acid blue 1; disulfine blue; sodium [[[(4-diethylamino)phenyl](2,4isulfonatophenyl)methylene]cyclohexa-2,5-dien-1-ylidene]diethylammonium, sulphan blue; C₂₇H₃₁N₂NaO₆S₂ = 566.6 (129-17-9)

Violet powder, soluble in water. Dilute solutions are blue and turn yellow on the addition of concentrated hydrochloric acid.