Glycerol (or glycerine, glycerin) is a simple polyol (sugar alcohol) compound. It is a colorless, odorless, viscous liquid that is widely used inpharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids known as triglycerides. Glycerol is sweet-tasting and of low toxicity.