Glycerol
Properties
| State | Liquid at room temperature (viscous) |
| Color | Colorless |
| Solubility | Miscible with water |
| Melting Point | 17.8 °C |
| Boiling Point | 290 °C |
About Glycerol
Glycerol is the three-carbon triol HOCH2-CHOH-CH2OH — molar mass 92.094 g/mol, viscosity around 1500 cP at 20 °C (about 1500× water), boils at 290 °C, and remains liquid down to 17.8 °C with serious supercooling tendencies that let it stay fluid well below freezing. Three hydroxyls per molecule mean dense intermolecular hydrogen bonding, which is why glycerol is hygroscopic enough to pull moisture out of dry air, miscible with water in any ratio, and so viscous it pours like honey. It's the alcohol backbone of every triglyceride in every fat and oil, so when you saponify tallow with NaOH to make soap, or transesterify rapeseed oil with methanol to make biodiesel, glycerol comes out as the byproduct — about 100,000 tonnes a year as biodiesel waste-stream alone, which has driven the price down enough that glycerol is now economically competitive as a feedstock for downstream chemistry like acrolein, propylene glycol, and epichlorohydrin synthesis. The most chemically interesting thing about glycerol is what happens when you nitrate it: dropwise addition to a 1:1 HNO3/H2SO4 mixed acid below 30 °C esterifies all three hydroxyls to give nitroglycerin, the shock-sensitive oily explosive that Nobel adsorbed onto kieselguhr to invent dynamite (and which cardiologists still prescribe sublingually because vascular endothelium reduces it to NO, dilating coronary arteries within seconds).
Where you'll encounter it
If you've ever rubbed lotion into dry skin in winter, vaped an e-liquid (the 'VG' on the bottle is vegetable glycerin), watched a pharmacist hand a heart patient a tiny bottle of nitroglycerin tablets, or smelled the sweet note in the steam off freshly washed dishes, you've used glycerol — it pulls water from the air to your skin, vaporizes cleanly in e-cig coils at 200-250 °C, nitrates to a coronary vasodilator, and is what makes commercial dishwashing detergent feel slippery.
Common Uses
- Humectant and viscosity modifier in skincare and toothpaste (E422)
- Base liquid in e-cigarette and vape formulations (vegetable glycerin)
- Cryoprotectant for sperm, embryo, and bacterial culture freezing (15% v/v final)
- Sweetener and moisture retainer in soft-textured pet treats and chewy candy
- Feedstock for nitroglycerin (dynamite, smokeless powder, vasodilator drug)
- Sublingual base for nitroglycerin tablets in angina pectoris treatment
- Lubricant and antifreeze in cold-weather hydraulic systems
Safety Information
GRAS for food, pharmaceutical, and cosmetic use; oral LD50 in rats is 12.6 g/kg, putting it in the 'practically nontoxic' bracket. No GHS hazard classification at typical concentrations. Real concerns are narrow: large oral doses (>1 g/kg) cause osmotic diarrhea because glycerol is poorly absorbed and pulls water into the gut lumen — this is why glycerin suppositories work as laxatives. Glycerol can be polyol-fermented by some gut bacteria into 3-hydroxypropionaldehyde (reuterin), which is irritating in concentrated form. Industrial-scale handling is unremarkable: not flammable below 160 °C flash point, not corrosive, no respiratory hazard. Vaping glycerol generates trace formaldehyde and acrolein when coil temperature exceeds 270 °C, which is the basis for low-power vape recommendations.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals. We deliberately do not publish occupational exposure limits or other regulatory thresholds: those values are revised over time and differ between jurisdictions, so the only correct source is the current SDS and the regulations that apply where you work.