The Meta-Encyclopedia

Glycerin

2 of the 6 encyclopedias on this shelf carry an entry for Glycerin. Both are reproduced below, so you can see where they agree and where they differ.

Collier's New Encyclopedia (1921)

or GLYCERINE, a triatomic alcohol of the fatty series, C3H8O3, or CH2 (OH)CH(OH)CH, (OH). Glycerin was discovered in 1778 by Scheele, ele, who obtained it in the preparation of lead plaster by saponifying lard with oxides of lead. Glycerin occurs in most natural animal and vegetable fats in combination with fatty acids, from which it can be obtained by saponifying with alkalies. It is also formed during the alcoholic fermentation of sugar. Pure glycerin is obtained by heating neutral fats in still, with a condensing apparatus, and passing steam in the melted fat, the temperature being kept below 600° F., and above 550° F.; the fat acids separate out in the receivers from the glycerin and water; the glycerin is then concenglycerin trated by evaporation. Glycerin is a thick, colorless, inodorous, neutral syrup, which has a very sweet taste; it mixes with water in all proportions, is soluble in alcohol and in chloroform, but insoluble in ether. Glycerin distilled with phosphorous pentachloride, P₂Cls, yields acrolein. By the action of a mixture of equal parts of concentrated nitric acid and sulphuric acid, it is converted into NITROGLYCERIN, CH₂O (NO₂) CHO (NO₂)CH2O (NO2) (q. v.). Glycerin is used for preserving fruits, also as a solvent for various salts, and in preparing copying-ink; also as a lubricator for machinery and and clockwork, and is placed over water in gas meters to prevent freezing, and is used for filling floating compasses. It is employed in the form of nitroglycerin in the preparation of dynamite, and for mixing with soap to form glycerin soap, which tends to soften the skin. Glycerin is used on account of its physical properties as an adjunct to lotions in the surface beskin diseases to prevent coming dry. It can be used as a substitute for sugar in the diet of diabetic patients.

Aiton's Encyclopedia (1910)

glis'er-in, a transparent, colorless liquid with the sweet taste and appearance of a sirup. Specific gravity 1.27. It is obtained from beef and other fats, notably palm oil, by the action of super-heated steam. Commercially it is a by-product in the manufacture of stearin candles. It consists of carbon, hydrogen, and oxygen, which, it may be remembered, is also the composition of alcohol. It mixes well with water and cannot be fermented. It freezes, but not readily, into white crystals. It is used in medicine to soften and soothe a sore throat, for instance. Glycerin salves, soaps, and cosmetics are excellent toilet articles, especially for chapped hands, rough face, or sores. As a salve it is particularly excellent. The reason is a simple one. Instead of drying up, glycerin attracts moisture from the air. Like alcohol and sirup, glycerin is fatal to the growth of bacteria, and may be used as a preservative for animal and plant substances. It is an important part of the explosive nitroglycerin. It is also used in the preparation of mucilage, in sizing paper, and in many manufactures. Glycerin is used as a remedy for nervous diseases and neuralgia. In order to obviate the objection to alcoholic medicines many remedies are compounded with glycerin. Since 1906 Ayer's Sarsaparilla, for instance, has been put up in a solution of glycerin instead of alcohol.

What Has Changed in the Last Century

Collier's in 1921 and Aiton's in 1910 both describe glycerin as essentially a by-product of the fat-splitting trade inh stearin candles and soap inh and that stayed true for most of the twentieth century. Since the 2000s the picture has inverted: biodiesel manufacture yields about a tenth of its output as crude glycerol, flooding the market and pushing producers to find new outlets for it rather than new sources. The chemical itself is unchanged, though it is now normally called glycerol, and it remains ubiquitous as a food humectant (additive E422), a cough-syrup and cosmetic base, and the feedstock for nitroglycerin. Two claims have not aged well: Aiton's confidence that glycerin is "fatal to the growth of bacteria" holds only at high concentrations, and Collier's suggestion that it can replace sugar for diabetics ignores that the body converts glycerol to glucose.

Written for this edition, 2026.