Propylene glycol, aswell alleged 1,2-propanediol or propane-1,2-diol, is an amoebic admixture (a diol or bifold alcohol) with blueprint C3H8O2 or HO-CH2-CHOH-CH3. It is a colorless, about odorless, clear, adhesive aqueous with a faintly candied taste, hygroscopic and miscible with water, acetone, and chloroform.
The admixture is sometimes alleged α-propylene glycol to analyze it from the isomer propane-1,3-diol HO-(CH2)3-OH, aswell alleged β-propylene glycol.
Properties
Propylene glycol is a basic in newer automotive antifreezes and de-icers acclimated at airports. Like ethylene glycol, the freezing point of baptize is depressed if alloyed with propylene glycol due to added befalling for hydrogen bonding. Unlike ethylene glycol, propylene glycol is of actual low toxicity. Both are readily biodegradable.
Propylene glycol is accepted to apply top levels of biochemical oxygen appeal (BOD) during abasement in apparent waters. This action can abnormally affect amphibian activity by arresting oxygen amphibian bacilli charge to survive. Ample quantities of attenuated oxygen (DO) in the baptize cavalcade are captivated if microbial populations decompose propylene glycol.
The oxygen burning abeyant of airport deicing operation discharges is abounding times greater than that of raw sewage. For example, afore application, Type I propylene glycol-based deicing aqueous is about adulterated to a admixture absolute about 50% propylene glycol. Pure propylene glycol has a five-day biochemical oxygen appeal (BOD5) absorption of about 1,000,000 mg/L. A archetypal adulterated propylene-based deicing aqueous could accordingly accept a BOD5 absorption of about 500,000 mg/L. In comparison, raw carrion about has a BOD5 absorption of about 200 mg/L. The bulk of aqueous acclimated to deice a individual jet depends on the attributes of the precipitation accident and the admeasurement of the aircraft but can ambit from several hundred to several thousand gallons. Therefore, deicing a individual jet can accomplish a BOD5 amount greater than that of one actor gallons of raw sewage. A ample hub airport generally has several hundred flights anniversary day.
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