. CERINE known also as hydrated oxide of lipyl, or hydrated oxide of glyceryl, was discovered by SCheele in 1779, who obtained it in the preparation of lead plaster, and named it " the sweet principle of oils." It is a colorless, viscid, neutral, uncrystallizable, inodorons fluid, of a sweet taste, is soluble in water and alcohol in all proportions, but is nearly insoluble in ether. Its specific gravity at 59° is, according to Miller and most authorities, 1.28, but Gorup-Besanaz makes it as high as 1.97. At 40° it becomes gummy and almost solid; at 212° it is slightly volatile; but if distilled alone, the greater part of it becomes decomposed; it may, however, be distilled without altera tion in a current of superheated steam which has been raised to a temperature of between 500° and 600°. By this means, Mr. Wilson* has succeeded in separating heated fats into hydrated glycerine, and the acids with which it was previously in combination; the glycerine is thus obtained in a high state of concentration as a colorless, sirupy liquid, which can be thus prepared in unlimited quantity.
Glycerine forms soluble compounds with baryta, strontia, and lime; and it disSolves oxide of lead and numerous salts. Berthollet has found that glycerine, like (q.v.), is convertible into a true fermentable sugar, when digested with certain animal tissues.
Glycerine occurs ready formed in a few fats (as, for example, old palm-oil), and, according to Pasteur, is contained in all fermented -liquors, and especially in wine, its quantity amounting to three per cent. of the fermented sugar. It is a product of the saponification of the various fats, although it does not exist as glycerine, but rather as a substance having the composition represented by the formula C611603. According to Berthollet's view, glyberine is a triatomic aleoliol;and may be represented by the formula C6IL03,3110; and in the animal and in many vegetable fats, the three atoms of water are replaced by three atoms of the anhydrous fatty acid. Thus Stearie Acid.
Stearine = 3C36lI3503, • Paltnitic Acid. • Palmitine = •Oleic Acid.
and Oleine = In the saponification of these fats—that is to say, when they are treated with potash, -soda, or oxide of lead, or under the influence of heated steam—the fatty acid separates from 0611603, which assimilates three atoms of water, and becomes glycerine.
We have already referred to the best mode (Wilson's process) of obtaining glycerine on a large scale: the usual method of obtaining it on a small scale is from olive oil, which we saponify by treating it with an equal weight of oxide of lead (litharge), which is mixed with water, and added to the oil, with which it is boiled till. the saponification is complete. The glycerine is dissolved by the water, and is easily separated from the insoluble lead-plaster (a mixture of oleate and palmitate of lead). Any traces of lead are removed by sulphureted hydrogen, and the water is then expelled in vacuo, or over the water-bath. The former is preferable, as iu the open air the glycerine becomes brown.
The uses of glycerine are numerous. In medicine, it is employed as a local appli cation in diseases of the skin and of the ear; and it is used internally as a solvent for many drugs. It is a valuable preservative fluid for small and delicate anatomical pre parations, and it has been applied to the preservation of meat. It has been added to the water in gas-meters, with the view of preventing it from freezing in winter, or from evaporating too rapidly in summer. It is used in the manufacture of copying-ink, and is of general application wherever a lubricating agent is required.
Many interesting researches have been carried on during the last few years regard ing the true chemical nature and the artificial production of glycerine; they are,,how ever, for the most part of a too purely chemical nature to be made intelligible to the general reader. We will merely remark that, like the alcohols in general, to which class glycerine is now assigned, it forms several classes or series of derivatives, the most important of which are its combinations with acids, forming glycerides, or com pound ethers of glycerine, which are analogous in their composition to the various fats and oils. Berthollet has succeeded in forming these bodies synthetically, and has thus not only reproduced several of the natural fats, but has obtained a large class of similar bodies which were not previously known.
Treated with sulphuric acid, glycerine yields sulphoglyceric acid (C6I,06,2503), and treated with phosphoric acid, it yields plcosphoglyceric acid HO), a sub stance which occurs normally, in combination with soda and ammonia, in the brain and in the yolk of egg.