Hexamethyldisiloxane (silyl ether, MM head capping agent), colorless transparent liquid, easy deliquescence. Insoluble in water, soluble in a variety of organic solvents. Used as silicone oil, silicone rubber, pharmaceuticals, gas chromatography fixed liquid, analytical reagents, hydrophobic agents, etc. It is prepared by hydrolysis of trimethylchlorosilane.