Diethylene glycol (DEG) is an odorless, colorless, clear and viscose liquid with a sweet taste, which is produced from the reaction between water and ethylene oxide. In fact, it is the co-product of ethylene glycol alongside with triethylene glycol (TEG). It is miscible with water, alcohols, acetone, ether and has the chemical formula of C₄H₁₀O₃.

In terms of chemicals properties, diethylene glycol is similar to MEG (mono ethylene glycol), but it has a higher specific gravity, viscosity and boiling point.