Colchiceine contains three methoxyl groups. It melts at 150°, dissolves but little in cold, copiously in boiling water. Colchiceine appears to be an acid, forming salts with the alkalies.
Zeisel[549] has formed acetotrimethylcolchicinamide (NHAcC15H9(OMe)3CONH3) by heating colchicine with alcoholic ammonia in closed tubes for four hours at 100°. The amide is crystallised from hot alcohol; it is readily soluble in dilute HCl, almost insoluble in water; when a strong hydrochloric acid solution of the amide is treated with a small amount of potassium nitrite a splendid violet colour is produced.
[549] Monatsh., ix. 1-30.
§ 509. Tests.—Ferric chloride, if added to an alcoholic solution of the alkaloid, strikes a garnet red; if to an aqueous solution a green or brownish-green; nitric acid added to the solid substance gives a violet colour. Erdmann’s reagent (nitrosulphuric acid) gives in succession green, dark blue, and violet colours, ultimately turning yellow, changed, on addition of an alkali, to raspberry-red. Mandelin’s reagent (1 grm. of ammonium vanadate in 200 grms. of sulphuric acid) gives a green colour.
§ 510. Pharmaceutical Preparations.—Colchicine itself is officinal in Austria—the wine in the British, French, and Dutch, and the seeds themselves in all the pharmacopœias. The wine of colchicum, officinal in nearly all the pharmacopœias, is made with very different proportions of seeds or bulbs.
The tincture of colchicum is officinal in our own and in all the Continental pharmacopœias; in the British, one part of seeds is exhausted by eight parts of proof spirit.
A tincture of colchicum seeds, examined by Johannson, contained ·18 per cent. of colchicine, and a tincture prepared from the bulbs ·14 per cent.
Colchicum vinegar is not officinal in Britain, but one containing 5·4 per cent. of acetic acid is so in the Netherlands, Germany, and France; the strength appears to be about ·095 per cent. of colchicine.