Glycerol
Chemical name	Propane-1,2,3-triol
Chemical formula	C3H8O3
Molecular mass	92.09 g/mol
Melting point	17.8 °C
Boiling point	290 °C
Density	1.261 g/cm3
CAS number	56-81-5
SMILES	OCC(O)CO

Glycerin, also known as glycerine and glycerol, and less commonly as 1,2,3-propanetriol, 1,2,3-trihydroxypropane, glyceritol, and glycyl alcohol is a colorless, odorless, hygroscopic, and sweet tasting viscous liquid. Glycerin has three hydrophilic alcoholic hydroxyl groups (-OH) that are responsible for its solubility water. Glycerin is prochiral. Glycerin is used in glycerin soap, in cosmetics and creams, in foods, in chemistry, and in glycerin mist.

Glycerin and triglycerides

Glycerol (3D model)

When referring to its function in living organism, the term glycerol is preferred. Glycerol is an important component of triglycerides (i.e. fats and oils) and of phospholipids. When the body uses stored fat as a source of energy, glycerol and fatty acids are released into the bloodstream. The glycerol component can be converted to glucose by the liver and provide energy for cellular metabolism.

A byproduct of saponification and transesterification to obtain biodiesel, this is produced by hydrolysis of three ester linkages and loss of three equivalents of fatty acid from fat or biological oil.

Fats and oils are insoluble in water, because the OH groups of glycerin are replaced by ester groups. They are hydrophobic.

Glycerin and biodiesel

As a byproduct of biodiesel production, each of the OH sites in HO-CH₂-CH(-OH)-CH₂-OH is one of the three places where an ester is broken off the triglyceride molecule.

See: transesterification.

Purification

Like biodiesel by-product, the purification of the lower glycerin phase involves: neutralisation, separation of unreacted methanol, dilution with wash liquid stream coming from methylester washing, splitting of soaps and final concentration up to 80%. Partially refined glycerin can be delivered as such to specialized distillers.

Feedstock pre-treatment and upgrading of glycerin to pharmaceutical grade (>99.7%) can be optionally implemented within the biodiesel factory itself.

Applications

Drugs

• Used in medical and pharmaceutical preparations, mainly as a means of improving smoothness, provide lubrication and humectant.
• Laxative suppositories, cough syrups, elixirs and expectorants.

Personal care

• Serves as a humectant, solvent and lubricant in personal care products
• Competes with sorbitol although glycerin has better taste and higher solubility.
• Toothpaste, mouthwashes, skin care products, hair care products and soaps

Glycerin is a component of glycerin soap, which is made from denatured alcohol, glycerin, sodium castorate (from castor), sodium cocoate, sodium tallowate, sucrose, water and parfum (fragance). Sometimes one adds sodium laureth sulfate. This kind of soap is used by people with sensitive, easily irritated skin because it prevents skin dryness with its moisturizing properties.

Foods and beverages

• Serves as humectant, solvent and sweetener, may help preserve foods.
• Solvent for flavors (such as vanilla) and food coloring.
• Humectant and softening agent in candy, cakes and casings for meats and cheeses.
• Manufacture of mono- and di-glycerides for use as emulsifiers
• Used in manufacture of polyglycerol esters going into shortenings and margarine.
• Used as filler in low-fat food products (i.e., cookies).

Polyether polyols

• One of the major raw materials for the manufacture of polyols for flexible foams, and to a lesser extent rigid polyurethane foams
• Glycerin is the initiator to which propylene oxide/ethylene oxide is added

Alkyd resins (plastics) and cellophane

• Used in surface coatings and paints
• Used as a softener and plasticizer to impart flexibility, pliability and toughness
• Uses include meat casings, collagen casings (medical applications)and nonmeat packaging
• Plasticizer in cellophane.

Absolute alcohol

• There is an absolute alcohol production process by dehydration using glycerin.

Other applications

• Manufacture of paper as a plasticizer, humectant and lubricant
• Humectant for pet foods to retain moisture and enhance palatability
• Used in lubricating, sizing and softening of yarn and fabric
• Used in de-/anti-icing fluids, as in vitrification of blood cells for storage in liquid nitrogen
• Patent applications have been filed for detergent softeners and surfactants based on glycerin (i.e., alkyl glyceryl ethers) instead of quaternary ammonium compounds.
• A way to preserve leaves is to submerge them in a solution of glycerin and water.

Use a mixture of one part glycerin to two parts water. Place the mixture in a flat pan, and totally submerge the leaves in a single layer in the liquid. You'll have to weigh them down to keep them submerged. In two to six days, they should have absorbed the liquid and be soft and pliable. Remove them from the pan and wipe off all the liquid with a soft cloth. Done correctly, the leaves will remain soft and pliable indefinitely.

• Can be added to solutions of water and soap to increase that solutions ability to generate bubbles that will last a long time.

See also: oleochemicals.

External links

• Glossary for the Modern Soap Maker (http://www.ccnphawaii.com/glossary.htm)
• Glycerin soap (http://www.gal.es)
• Absolute alcohol using glycerin (http://journeytoforever.org/biofuel_library/Mariller.html)

Glycerine is also the title of a single from the album Sixteen Stone by the band Bush.