PEG 400 is a low-molecular-weight grade of polyethylene glycol. It is a clear, colorless, viscous liquid. Due in part to its low toxicity, PEG 400 is widely used in a variety of pharmaceutical formulations.

Density: 1.13 g/cm³, Formula: C2nH4n+2On+1,n=8.2to9.1

PEG 400 (polyethylene glycol 400) is a low-molecular-weight grade of polyethylene glycol. It is a clear, colorless, viscous liquid. Due in part to its low toxicity, PEG 400 is widely used in a variety of pharmaceutical formulations. More recently, it has been used to make "E-Liquid" for electronic cigarettes (personal vaporizers).