Physical and chemical properties :The scientific name of propylene glycol is “1,2-propylene glycol”. Chemical formula CH3CHOHCH2OH. Molecular weight 76.10. There is a chiral carbon atom in the molecule. The racemic body is a hygroscopic viscous liquid with a slightly spicy taste. Specific gravity 1.036 (25/4℃), freezing point -59℃. Boiling point 188.2℃, 83.2℃ (1,333 Pa Chemicalbook), miscible in water, acetone, ethyl acetate and chloroform, soluble in ether. It can be dissolved in many essential oils, but it is immiscible with petroleum ether, paraffin and grease. It is relatively stable to heat and light, and more stable at low temperatures. The boiling point of the left-handed body is 187~189℃, and the specific rotation [α] D20-15.0°. Propylene glycol can be oxidized to propionaldehyde, lactic acid, pyruvic acid and acetic acid at high temperatures.