Tripropylene Glycol or TPG is mixture of isomers present as a clear liquid, odorless and with a medium viscosity. It’s naturally hygroscopic (it attracts water from atmosphere). It is completely soluble in water and miscible with many organic solvents. The molecular formula is C9H20O4. Tripropylene glycol is a by-product of the manufacture of monopropylene glycol. At high temperature and pressure, water is added to propylene oxide, which results in the formation of mono propylene glycol (90%) and mixture of propylene glycol and tripropylene glycol (10%).