Mono ethylene glycol (MEG) (CAS No. 107‑21‑1; formula C₂H₆O₂; MW 62.07 g/mol) is a colorless, viscous, hygroscopic liquid (mp ≈ –12.9 °C; bp ≈ 197.6 °C). It’s fully miscible with water, widely used as a polyester and PET resin intermediate, antifreeze/coolant base, industrial heat-transfer fluid, and humectant in multiple industries.