C3H8O3 = 92.064.
Glycerin, or glycerol, is obtained by the action of alkalies or superheated steam on fats or fixed oils, and consists of the trihydric alcohol, glycerol, C3H5(OH)3, mixed with a small proportion of water. It is also official in the U.S.P., when it should contain not less than 95 per cent. of absolute glycerol, and its specific gravity be not less than 1.246 at 25°. Glycerin occurs as a clear, colourless, odourless, hygroscopic liquid of syrupy consistence and a sweet taste; neutral to litmus. Specific gravity, 1.260. Glycerin should not contain more than 1 part of arsenic in 250,000, and usually contains considerably less.
Miscible with water or alcohol; insoluble in ether, chloroform, or oils.
Action and Uses.—Applied to the skin, glycerin acts as an emollient, somewhat resembling the fats in its action, though more irritating. If the skin be abraded, some smarting arises; for its emollient action, glycerin should therefore be diluted with one or two volumes of rose water. For chilblains, chapped hands, and in eczema and prurigo, glycerin of starch is an excellent emollient. Applied undiluted to mucous membranes, it takes up moisture from the mucous secretions and increases the penetrative action of any drugs held in solution. It is applied on a tampon (often with ammonium ichthosulphonate) in congestion of the cervix uteri. If 4 to 15 mils (1 to 4 fluid drachms) of glycerin be injected into the rectum, it augments peristalsis and produces an evacuation of the bowels. The effect is reflex, and is set up by the local irritation arising from absorption of moisture from the mucous surfaces. Suppositories of glycerin have a similar effect (see Suppositoria Glycerini). Taken internally, glycerin is demulcent, laxative, antiseptic, and to a slight extent nutritious. It is a favourite constituent of soothing linctuses for use against cough, and in the form of pastilles prepared with a gelatin basis and flavoured with fruit pastes and essences or medicated with astringents and antiseptics, it is the commonest emollient for the throat. Glycerin is employed as a sweetening agent in place of syrup, especially with ferric chloride and preparations of cascara or cinchona; it renders galenical preparations of the latter drugs more miscible with water. It is Also used in place of sugar to sweeten the food of diabetic patients. Glycerin has remarkable powers as a solvent and preservative, and is therefore applied to innumerable pharmaceutical uses. It forms the basis of the so-called "aqueous" or non-alcoholic tinctures, and is largely employed as an antiseptic in the preparatino of solutions of the digestive ferments and other glandular secretions.
Dose.—4 to 8 mils (1 to 2 fluid drachms).
- Lotio Glycerini Composita, B.P.C.—COMPOUND GLYCERIN LOTION.
- An agreeable lotion for the skin. If about one-tenth of the distilled water in this lotion be replaced by neutral cucumber juice, the product will resemble preparations sold under the name of "Glycerin and Cucumber".
- Suppositoria Glycerini, B.P.—GLYCERIN SUPPOSITORIES.
- Glycerin, by weight, 71; gelatin, cut small, 14.2; distilled water, a sufficient quantity. Cover the gelatin with water in a weighted evaporating dish; allow it to stand for two minutes, pour off the excess of water, set aside until the gelatin is softened, add the glycerin, and heat on a water-bath until solution is effected; evaporate until the product weighs 102, and pour into moulds having a capacity of 1, 2, 4, or 8 grammes (15, 30, 60 or 120 grains). The suppositories should be prepared as required. Each of these suppositories contains nearly 70 per cent. of glycerin. Glycerin suppositories are used to evacuate the bowels. They absorb water from the tissues of the lower part of the rectum, increased peristalsis being set up reflexly by the irritation so produced. The suppositories are prepared to contain 1, 2, 4, or 8 grammes of the mass, the smaller sizes being used for infants and children, the larger for adults. Their use should be an occasional measure only, or they may cause rectal irritation.
- Suppositoria Glycerini, U.S.P.—SUPPOSITORIES OF GLYCERIN.
- Glycerin, 30 grammes; monohydrated sodium carbonate, 0.5 grammes; stearic acid, 2 grammes; water, 5 mils. Dissolve the carbonate in the water and heat the solution on a water-bath with the glycerin and stearic acid until effervescence ceases and the liquid is clear. Divide the melted mass into ten suppositories, each of which will contain 3 grammes (45 grains) of glycerin.
- Suppositoria Glycerini Saponata, B.P.C.—SOAP GLYCERIN SUPPOSITORIES.
- Each suppository contains 90 per cent. of glycerin.
The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.