Propylene glycol is a viscous, colourless liquid. It is almost odorless and has a faintly sweet taste. Its chemical formula is CH3CH(OH)CH2OH. As it contains two alcohol, it is classified as a diol; diol may also be called a glycol. It is with a broad range of solvents, including water, acetone, and chloroform. In general, glycols are non-irritating and have very low volatility.
For certain uses as food additive, propylene glycol is considered as by the US Food and Drug Administration, and is approved for food manufacturing. In the European Union, it has E1520 for food applications. For cosmetics and pharmacology, the number is E490. Propylene glycol is also present in propylene glycol alginate, which is known as E405.
Propylene glycol, vegetable glycerine(e), or a mixture of both, are the main ingredients in e-liquid used in electronic cigarettes. They are aerosolized to resemble smoke and serve as carriers for substances such as nicotine and flavourants.
Propylene glycol is approved and used as a vehicle for topical, oral, and some intravenous pharmaceutical preparations in the US and Europe.
