Glycerin is obtained by the reaction of fats and fixed oils with watery alkaline fluids. Chemically it is classed with the alcohols. It is always set free in the process of soap-making as a waste product, and so made is purified and sold, though the larger part of the glycerin in commerce is manufactured directly by the decomposition of fats by heated steam.

Glycerin absorbs water from the air and mixes with water in all proportions. If pure it cannot become rancid.

Applied externally it is unirritating to the sound skin, but painful if there be any abrasions.

It is slightly stimulant and antiseptic, and tends to make the skin dry and brittle. It is readily absorbed when applied externally.

Internally it has no special effect on the stomach, but is supposed to have some nutritive power. It is produced normally in the intestines during the digestion of oils and fats. If administered in free doses it has a laxative action, and for this purpose is given alone, or in combination with castor oil.

The laxative action is very notable when glycerin is administered as an enema; a small amount - ʒ ss.- ℥ ii. - acts quickly and satisfactorily.

Glycerin suppositories are also, in most instances, very efficacious. Average dose, ʒ i.-4 mils.

Preparations

Glyceritum Phenolis. Glycerite of Phenol.

Contains 20 parts of phenol to 80 of glycerin.

Glyceritum Acidi Tannici. Glycerite of Tannic Acid.

The same strength as the above.

Glyceritum Boroglycerini. Glycerite of Boroglycerin.

Boric acid 3 parts to 7 of glycerin.