Methylene blue

CI 52015, 3,7-Dimethylaminophenothiazin-5-ium chloride; C₁₆H₁₈ClN₃S,xH₂O = 319.9 (anhydrous) (122965-43-9)

It occurs in different hydrated forms and may contain up to 22% of water. A dark-green or bronze, crystalline powder, freely soluble in water, soluble in ethanol (96%).