Propylene Glycol C3H8(SO4)2   Properties:  Colorless, viscous, stable, hygroscopic liquid; practically odorless and tasteless; miscible with water, alcohols, and many organic solvents.  Bp 187.3C, fp –60C, d 1.0381 at 20/20C, bulk d 8.64 lb/gal (20C), refr index 1.4293 (27C), surface tension 40.1 dynes/cm (25C), viscosity 0.581 poise (20C), vap press 0.07 mm (20C), specific heat 0.590 cal/g (20C), latent heat of evaporation 168.6 cal/g at bp, flash p (OC) 210F (99C), autoign temperature 780F (415C), heat of combustion temperature 431.0 kg cal/mole.  Combustible.