It burns with a clear flame like oil, if there be free access of air, and a high temperature for kindling it.
From one point of view, in its chemical relations it is an alcohol, and although the ferments that excite alcoholic fermentation will not ferment pin e glycerine, it may be fermeoted by a hitherto undescribed bacterium. Just as ac,etio acid and alcohol, interacting, form water and acetio ether, so acetic acid and glycerine, interacting, form water and monacetin. Triacetin is a natural glyceride, occurring in cod-liver-oil. This brings to mind the other aspect of glycerine, viz. as the base of the natural glycerides, in which, it requires three equivalents of a fatty acid, and hence is considered a tri-aeid base, or, in the language of modern chemistry, trivalent alcohol radicle. Its formula on this view is ealla(011) and its relation to its most abundant sourcee is here shown : Tristearin Ca11, (0C, allaa0)a Tallow.
Triolein Calla (Cele/1530)i Tripalmitin Calla (001a1410)3 . .. Palm-oil.
Triricinolein Calla (0Cialla300, .. Castor-oil.
Tributyrin C3Ela (0C,11,0)3 Butter.
Trirtectin Calla (0C217130)3 Cod-liver-oil.
Next to water, glycerine is the most powerful solvent known. It dissolves bromine, iodine, and oarbolic acid better than water does. 'Hever gives a long table of the solubilities of different substances in 100 parts of glycerine, from which the following is taken :-93 sodium carbonate, 40 alum, 25 green vitriol (ferrous sulphate), 20 lead acetate, 20 sodium chlorate, 0.50 quinine and other alkaloids, 1.9 iodine, 0.20 phoephorus, 0.10 sulphur.
With barytti, strentia, and lime, it forms compounds iosoluble in water, not precipitable by carbonio acid. Anhydrous glycerine diesolves caustic potash and soda, oxide of lead, all deliquescent salts, the sulphates and chlorides of potassium and sodium, and of copper, the vegetable acids and alkaloids. It mixes with water in all proportions; the following table will be found very useful commercially : Commercial glycerine is liable to contain various impurities, arising from its mode of prepara tion ; also certain adulterants, of which cane-sugar and glucose are the chief. Glucose may be detected by the brown colour formed when the suspected glycerine is boiled with caustic soda ; cans-sugar is shown by its deposition when the glyeariee is agitated with chloroform, or, more certainly, by a polariziog saccharimeter, since glycerine has no mtatory action on the plane of polarization. Lead is deteeted by sulphuretted hydrogen ; lime, by the addition of alcohol and
sulphuric acid, a white precipitate of calcium sulphate being formed ; butyric and formic acids, by the characteristic smell of their ethers, produced by boiling the suspected glycerine with alcohol and strong sulphuric acid ; oxalic acid by the addition of calcium chloride and ammonia ; sodium chlmide, by the addition of silver nitrate, which should give no precipitate witla pure glycerine after 24 hours' standing. A rough and ready test for impurities generally is to agitate the glycerine with an equal bulk of chloroform, when they collect in the intermediate layer.
Traces of glycerine present in other substances, may be detected by the formation of formic ether (which smells of peach-blossom), produced by boiling glycerine with manganese binoxide, alcohol, and sulphuric acid.
The uses of glycerine are very numerous, and are almost daily increasing in number. Its ap plications in phartnacy are almost endless ; it is used wherever a snbstance requires to be kept more or less moist, e. g. modelling-clay, tobacc,o, paper for printing, adhesive guin, &c.; also in spinning, " dressing," weaving, rope-making, and tanning. It is used in gas-meters, and in floating compasses, to lower the freezing-point of the water therein used ; it is an excellent preservative medium for meat, and for natural history specimens, to which latter purpose it was first applied in 1856 by Dr. Carpenter, F.R.S. Glycerine is also of great importance as the starting-point of other chemical products of great value, one of the most valuable of which is nitro-glycerine, the fabri cation of which bas been described on pp. 897-902. For this purpose, it must coritain no sodium chloride. The engineers of the Panama canal estimate their requirements of nitro-glycerine at a minimum of 8000 tons, equal to about half that quantity of raw glycerine. Besides nitre glycerine, two other important products are obtainable from glycerine, viz. isopropyl iodide, and allyl iodide, each of which serves as the starting-point of a large series of chemical products, many of them of utility in the arts. They are formed by heating glyc,erine with hydriodic acid, thus :