The potassium compound melts at 90°, the sodium at 159°-160°. The alkaloid is regenerated when the alkali salts are treated with acids or with CO2. Crude narceine may be purified by means of the sodium salt; the latter is dissolved in alcohol and precipitated with ether.
It is soluble in alcohol, but almost insoluble in alcohol and ether, or benzene and ether; it is slightly soluble in ether, carbon disulphide, and chloroform. It has no reaction on moist litmus paper.
Benzole and petroleum ether extract narceine neither from acid nor alkaline solutions; chloroform extracts narceine both from acid and from alkaline solutions, the latter in small proportion only. Narceine turns the plane of polarisation to the left, [α]r = 66·7°. Narceine may be separated from narcotine by the addition of ammonia to the acid aqueous solution; narcotine is fully precipitated by ammonia, but narceine is left in solution.
In the subliming cell it melts at 134°, but gives no crystalline sublimate. The tube melting-point of the trihydrate is 170°. The melted substance is at first colourless; but on raising the temperature, the usual transitions of colour through different shades of brown to black are observed. If melted, and kept a few degrees above its melting-point, and then cooled slowly, the residue is straw-coloured, divided into lobes, most of which contain feathery crystals.
At high temperatures narceine develops a herring-like odour; the residue becomes darkish blue with iron chloride. Concentrated nitric acid dissolves it with a yellow colour; on heating, red vapours are produced; the fluid contains crystals of oxalic acid, and develops with potash a volatile base. Concentrated sulphuric acid colours pure narceine brown; but if impure, a blood-red or blue colour may be produced. It does not reduce iron salts.
Fröhde’s reagent colours it first brown-green, then red, passing into blue. Narceine forms precipitates with bichromate of potash, chloride of gold, bichloride of platinum, and several other reagents. The one formed by the addition of potassio zinc iodide is in hair-like crystals, which after twenty-four hours become blue.
Weak iodine solution colours narceine crystals a black-blue; they dissolve in water at 100° without colour, but on cooling again separate with a violet or blue colour. If on a saturated solution of narceine a particle of iodine is strewn, fine needle-like grey crystals form around the iodine. A drop of “Nessler” solution, added to solid narceine, at once strikes a brown colour; on diluting the drop with a little water, beautiful little bundles of crystals appear.—Flückiger.
The following group reagents precipitate narceine:—picric acid, tannin solution, and potassium dichromate on long standing. The following give no precipitate:—mercuric cyanide, mercuric potas. iodide, mercuric chloride, mercuric bromide, and potas. ferrocyanide solutions.
§ 371. Effects.—The physiological action of narceine has been variously interpreted by different observers. Claude Bernard[408] thought it the most somniferous of the opium alkaloids. He said that “the narceinic sleep was characterised by a profound calm and absence of the excitability of morphine, the animals narcotised by narceine on awaking returning to their natural state without enfeeblement of the hind limbs or other sequelæ.” It has been amply confirmed that narceine possesses somniferous properties, but certainly not to the extent that Bernard’s observations led physiologists to expect. In large doses there is some irritation of the stomach and intestines, and vomiting occurs, and even diarrhœa; moderate doses induce constipation. The maximum medicinal dose may be put at ·14 grm. (or 2·26 grains), and a probably dangerous dose would be three times that quantity.[409]