"Propylene glycol, also called 1,2-propanediol or propane-1,2-diol, is an organic
compound (a diol or double alcohol) with formula C3H8O2 or HO-CH2-CHOH-CH3. It is a colorless, nearly odorless, clear, viscous liquid with a faintly sweet taste, hygroscopic and miscible with water, acetone, and chloroform."
"The compound is sometimes called α-propylene glycol to distinguish it from the isomer propane-1,3-diol HO-(CH2)3-OH, also called β-propylene glycol."