Uses

Glycerin has the ability to attract water through osmosis. Water "follows" the glycerin, which is why it has a variety of uses including reducing intracranial pressure, osmotic diuresis, topical skin application, laxative and for reducing intraoccular pressure in the form of eye drops for glaucoma. It is also used as a pharmaceutical excipient.

Glycerin is available over the counter as a vicious liquid and is used topically as a moisturizer, humectant or emollient. Glycerin forms a layer on the skin which keeps moisture form evaporating and escaping, holding the moisture in the skin layer. It is used to protect against dryness and irritation. It can pull water towards itself bringing water toward the upper layer of the skin. Read the manufacturers instructions or consult with a doctor or pharmacist for instructions on how to use.

Studies are demonstrating that glycerin guides the cell maturation process in a way that is beneficial to conditions such as psoriasis, where the skin has an increased "turn over" and the skin cells are shed too quickly.

Glycerin is available over the counter in suppository form as a laxative.

Glycerin is used for its osmotic effects in reducing intracranial pressure, as an osmotic diuretic, and for reducing intraoccular pressure in the form of eye drops for glaucoma.


Chemistry

Chemical Formula: C3H8O3

Molecular Weight: 92.094

Boiling point: 290 deg C

melting point: 18.1 deg C

IUPAC name: propane-1,2,3-triol

Density 1.2613 g/ml at 20 C

Physical properties:It is a clear, odorless, viscous liquid at room temperature. It is hygroscopic, meaning that it absorbs atmospheric water. It has a sweet taste.

Solubility:It is soluble in water acetone, ethanol and ethyl ether.

pKa =14.4

The chemical name of glycerin is 1, 2, 3-propanetriol. Glycerin contains three hydroxyl groups attached to a saturated three carbon skeleton. When heated to a high temperature, it decomposes with the release of acrolein, which is a toxic substance. At very low temperatures it may form crystals.

When a triglyceride is hydrolyzed in the presence of an aqueous base and then acidified, it yields glycerol and three carboxylic acid molecules. A similar reaction to this is seen in the production of soaps.

Glycerol is converted to L-Glycerol 3- Phosphate by glycerol kinase. In the human body, L-Glycerol 3- Phosphate is the precursor for triglyceride(triacylglycerol) synthesis.


Saponification

Soaps are created through saponification. Saponification is a process that utilizes fat molecules, often taken from the fat layer of cattle meat. The fatty substance is steamed in order for the fat to melt and an upper layer is formed. This upper layer is called tallow and is used in saponification. Coconut oil may also be used.

The first step in the process of saponification involves the boiling of these triglycerides(fats) with sodium hydroxide(an aqueous base). Triglycerides (triacylglycerols) have a glycerol backbone bound to 3 fatty acid chains by ester linkages. The purpose of the base is to hydrolyze the ester functional groups of the triglyceride molecules(saponification). This reaction yields glycerin and the sodium soap. Next, sodium chloride(NaCl) is added, which removes the sodium ion from the sodium soaps creating a precipitate of the soap. The glycerin and water are then removed from the mixture by distillation processes, leaving a mixture containing mostly soap, sodium chloride, and sodium hydroxide. Next is a purification process done by boiling the soap mixture and adding more sodium chloride. After this process other treatments may be used depending on the desired PH and use of the soap.


Alkyd Resins

Ophthalmic anhydride and glycerol are combined and heated to produce a alkyd resins. Alkyd resins are thermoplastic polyesters that are used as weather coatings and in paints.


Glycerogelatins

Glycerogelatins are produced by mixing water and gelatin and heating to dissolve the gelatin. Once the gelatin is dissolved, a mixture of glycerin and the medical agent is incorporated and the mixture is stirred as it cools to allow congealing. Glycerogelatins are used as a topical delivery system which are intended to remain on the skin for long periods of time(weeks). They are melted before application and cooled until close to temperature of the body, at which point they are applied to the skin, usually using a brush or other tool. They then dry and a bandage is placed over the area.


Sources

1. National Center for Biotechnology Information. PubChem Compound Database; CID=753, https://pubchem.ncbi.nlm.nih.gov/compound/753 (accessed May. 19, 2017)

2. Allen, Loyd V., and Howard C. Ansel. Ansel's Pharmaceutical Dosage Forms and Drug Delivery Systems (10th Edition). Baltimore, MD: Wolters Kluwer Health, 2014. Print.

3. Brown, William Henry, Brent L. Iverson, Eric V. Anslyn, and Christopher S. Foote. Organic Chemistry. Australia: Cengage Learning, 2009. Print.br />