§ 366. Narcotine (C22H23NO7) crystallises out of alcohol or ether in colourless, transparent, glittering needles, or groups of needles, belonging to the orthorhombic system.
It is only slightly soluble in boiling, and almost insoluble in cold water. One part requires 100 parts of cold, and 20 of boiling 84 per cent. alcohol; 126 parts of cold, 48 of boiling ether (specific gravity 0·735); 2·69 parts of chloroform; 400 of olive oil; 60 of acetic ether; 300 of amyl alcohol; and 22 parts of benzene, for solution. The neutral solution of narcotine turns the plane of polarisation to the left [α]r = 130·6; the acid solution to the right. Narcotine has no effect on red litmus paper.
Narcotine gives no crystalline sublimate; its behaviour in the subliming cell is described at [p. 259]. Its melting-point, taken in a tube, is about 176°.
Behaviour of Narcotine with Reagents.—Narcotine, dissolved in dilute hydrochloric acid, and then treated with a little bromine, gives a yellow precipitate, which on boiling is dissolved; by gradually adding solution of bromine and boiling, a fine rose colour is produced, readily destroyed by excess of bromine. This is perhaps the best test for the presence of narcotine. Concentrated sulphuric acid dissolves narcotine; the solution in the cold is at first colourless, after a few minutes yellow, and in the course of a day or longer the tints gradually deepen. If the solution is warmed, it first becomes orange-red, then at the margin violet-blue; and if heated until hydric sulphate begins to volatilise, the colour is an intense red-violet. If the heating is not carried so far, but the solution allowed to cool, a delicate cherry-red hue slowly develops. If the sulphuric acid solution contains 1 : 2000 of the alkaloid, this test is very evident; with 1 : 40,000, the colour is only a faint carmine.—A. Husemann.
A solution of narcotine in pure sulphuric acid, to which a drop of nitric acid has been added, becomes of a red colour; if the solution is warmed to 150°, hypochlorite of soda develops a carmine-red; and chloride of iron, first a violet, then a cherry-red. The precipitants of narcotine are—phosphomolybdic acid, picric acid, sulphocyanide of potash, potassio cadmic iodide, mercuric chloride, platinic chloride, auric chloride, and several other reagents.
From the brown mass left after heating narcotine above 200°, hydrochloric acid extracts a small portion of a base but little studied. The residue consists of humopic acid (C40H19O14), which can be obtained by dissolving in caustic potash, precipitating with HCl, dissolving the precipitate in boiling alcohol, and finally throwing it down by water.
§ 367. Effects.—Narcotine in itself has toxic action only in rather large doses; from 1 to 2 grms. have been given to man, and slight hypnotic effects have followed. It is poisonous in very large doses; an ordinary-sized cat is killed by 3 grms. The symptoms are mainly convulsions.
§ 368. Codeine (Codomethylene), C17H17OCH3(OH)NO + H2O, is the methyl of morphine; it is an alkaloid contained in opium in small quantity only. Mulder, indeed, quotes ·66 to ·77 per cent. as present in Smyrna opium, but Merck and Schindler give ·25 per cent. Schindler found in Constantinople, ·5 per cent.; and Merck, in Bengal, ·5 per cent. also.
Codeine crystallises out of dry ether in small, colourless, anhydrous, crystals; but crystallised slowly from an aqueous solution, the crystals are either in well-defined octahedra, or in prisms, containing one atom of water, and melting in boiling-water to an oily fluid. The anhydrous crystals have a melting-point of 150°, and solidify again on cooling. Its watery solution is alkaline to litmus paper.
It requires 80 parts of cold, 17 of boiling water, 10 parts of benzole, and 7 parts of amyl alcohol respectively, for solution. Alcohol, benzene, ether, carbon disulphide, and chloroform freely dissolve it, but in petroleum ether it is almost insoluble. Further, it is also soluble in aqueous ammonia, and in dilute acids, but insoluble in excess of caustic potash or soda, and may thus be thrown out of an aqueous solution. A solution of codeine turns the plane of polarisation to the left, [α]r = 118·2°.