Polyethylene Glycol, (C2nH4n+2On+1), is synthesized by ring-opening polymerization of ethylene oxide. This synthesis process gives PEG a range of molecular weights and distributions from 300 grams per mole to 10,000,000 grams per mole.PEG 400 has a molecular weight of 400 and is a clear, colorless, viscous liquid. Polyethylene Glycol is colorless, inert, odorless, and non-volatile. PEG is biocompatible (it won’t damage tissues or cells), hydrophilic, dissolves readily in water without changing the color odor or taste, and is nontoxic. Due to the high purity of Polyethylene Glycol 400, it is certified by the United States Pharmacopeia (USP) grade and the Food Chemicals Codex (FCC) grade.