CAS Number 56-81-5

Having been assigned since 1965 by the Chemical Abstracts Service (CAS), founded in 1907 as a subdivision of the American Chemical Society, the internationally recognized CAS number serves for unambiguous identification of the chemical substance it designates. However, the number is not sufficient to distinguish different purities or qualities.

Each CAS number consists of three numbers separated by hyphens. The first one contains up to seven, the second one always two numbers. The one-digit third number represents a checksum by which the entire number can be checked for plausibility. The assignment of CAS numbers does not follow an intrinsic order but is made in ascending order.

At room temperature, glycerin is a colorless and odorless viscous liquid that tastes sweetish and is hygroscopic. With its three hydroxyl groups, the substance belongs to the trivalent alcohols. Since the glycerin molecule features a strong polarity, it is well water-soluble. It is insoluble, however, in ether, petroleum ether, chloroform and fat oils. Water-free glycerin crystallizes below the melting point of 17.8 °C.

Thanks to its three OH groups, glycerin is highly reactive. When exposed to heat, it generates white steam. It first reacts with dried potassium permanganate under fume formation and strong heat buildup. Exceeding the ignition temperature results in self-ignition. The glycerin oxidizes to carbon dioxide, water, manganese dioxide and potassium carbonate. In addition, other compounds can form, for instance brown manganese(III)oxide or green potassium manganate(VI).

In combination with nitric acid, glycerin acid is formed. However, when a nitrifying acid from fuming nitric acid and concentrated sulfuric acid is used, glycerol trinitrate is formed, better known as the explosive nitroglycerin.

Since it absorbs water, pure glycerin is an important component in cosmetics articles such as ointments, moisturizing creams, and toothpastes. It not only keeps the skin smooth, but also prevents it from dehydration thanks to its hygroscopic properties. Under the E number 422, glycerin is added to foodstuff that must not dry out such as marzipan, chewing gum, or margarine.

Glycerin with the CAS number 56-81-5 is an outstanding softener, which, for instance, is admixed to starch-based foils so that they will not become brittle. Moreover, it serves as an antifreeze, lubricant and as a reactant in the production of dyes, plastics, and microchips. In addition, it attracts ever increasing interest as feedstuff for chickens, ruminants, and pigs.

A further important field of application for glycerin is medicine. It is infused as a 10-percent solution to treat cerebral edema. In the form of suppositories, it serves as laxative. Moreover, 56-81-5 is used in pharmaceutics as a solvent, solubilizer, humectant, and softener.