(Methylene Blue.)

Chemically, it is tetramethylthionine hydrochloride.

Properties. - Dark-green, crystalline powder, or prismatic crystals having a bronze-like luster. Readily soluble in water, somewhat less so in alcohol; the solutions are of a deep-blue color. Incompatible with potassium iodide. Reducing agents decolorize it. It is not to be confounded with commercial methylene blue, which is often the zinc chloride double salt of tetramethylthionine, is employed as a dye or stain, and is unfit for internal administration.

Dose. - Average dose: 4 grains 0.250 Gm. = 250 milligrammes, U. S. P.

Therapeutics. - It is an intercellular antiseptic, useful in destroying the malarial parasite. It is also of value in genito-urinary practice.