Diiodomethane or methylene iodide, commonly abbreviated "MI", is an organoiodine compund . Diiodomethane is a colorless liquid; however, it decomposes upon exposure to light liberating iodine, which colours samples brownish. It is slightly soluble in water, but soluble in organic solvents. It has a relatively highrefractive index of 1.741, and a surface tension of 0.0508 N•m−1.