(R. L.*)
| The Glutton, or Wolverine (Gulo luscus). |
GLYCAS, MICHAEL, Byzantine historian (according to some a Sicilian, according to others a Corfiote), flourished during the 12th century A.D. His chief work is his Chronicle of events from the creation of the world to the death of Alexius I. Comnenus(1118). It is extremely brief and written in a popular style, but too much space is devoted to theological and scientific matters. Glycas was also the author of a theological treatise and a number of letters on theological questions. A poem of some 600 “political” verses, written during his imprisonment on a charge of slandering a neighbour and containing an appeal to the emperor Manuel, is still extant. The exact nature of his offence is not known, but the answer to his appeal was that he was deprived of his eyesight by the emperor’s orders.
Editions: “Chronicle and Letters,” in J. P. Migne, Patrologia Graeca, clviii.; poem in E. Legrand, Bibliothèque grecque vulgaire, i.; see also F. Hirsch, Byzantinische Studien (1876); C. Krumbacher in Sitzungsberichte bayer. Acad., 1894; C. F. Bähr in Ersch and Gruber’s Allgemeine Encyklopädie.
GLYCERIN, Glycerine or Glycerol (in pharmacy Glycerinum) (from Gr. γλυκύς, sweet), a trihydric alcohol, trihydroxypropane, C3H5(OH)3. It is obtainable from most natural fatty bodies by the action of alkalis and similar reagents, whereby the fats are decomposed, water being taken up, and glycerin being formed together with the alkaline salt of some particular acid (varying with the nature of the fat). Owing to their possession of this common property, these natural fatty bodies and various artificial derivatives of glycerin, which behave in the same way when treated with alkalis, are known as glycerides. In the ordinary process of soap-making the glycerin remains dissolved in the aqueous liquors from which the soap is separated.
Glycerin was discovered in 1779 by K. W. Scheele and named Ölsüss (principe doux des huiles—sweet principle of oils), and more fully investigated subsequently by M. E. Chevreul, who named it glycerin, M. P. E. Berthelot, and many other chemists, from whose researches it results that glycerin is a trihydric alcohol indicated by the formula C3H5(OH)3, the natural fats and oils, and the glycerides generally, being substances of the nature of compound esters formed from glycerin by the replacement of the hydrogen of the OH groups by the radicals of certain acids, called for that reason “fatty acids.” The relationship of these glycerides to glycerin is shown by the series of bodies formed from glycerin by replacement of hydrogen by “stearyl” (C18H35O), the radical of stearic acid (C18H35O·OH):—
The process of saponification may be viewed as the gradual progressive transformation of tristearin, or some analogously constituted substance, into distearin, monostearin and glycerin, or as the similar transformation of a substance analogous to distearin or to monostearin into glycerin. If the reaction is brought about in presence of an alkali, the acid set free becomes transformed into the corresponding alkaline salt; but if the decomposition is effected without the presence of an alkali (i.e. by means of water alone or by an acid), the acid set free and the glycerin are obtained together in a form which usually admits of their ready separation. It is noticeable that with few exceptions the fatty and oily matters occurring in nature are substances analogous to tristearin, i.e. they are trebly replaced glycerins. Amongst these glycerides may be mentioned the following: