§ 412. Extraction from Organic Matters, or the Tissues of the Body.—Dragendorff states that, from as little as half a grain of the root, both gelsemine and gelsemic acid may be extracted with acid water, and identified. On extracting with water acidified with sulphuric acid, and shaking up the acid liquid with chloroform, the gelsemic acid (æsculin?) is dissolved, and the gelsemine left in the liquid. The chloroform on evaporation leaves gelsemic acid in little micro-crystals; it may be identified by (1) its crystallising in little tufts of crystals; (2) its strong fluorescent properties, one part dissolved in 15,000,000 parts of water showing a marked fluorescence, which is increased by the addition of an alkali; and (3) by splitting up into sugar and another body on boiling with a mineral acid. After separation of gelsemic acid, the gelsemine is obtained by alkalising the liquid, and shaking up with fresh chloroform; on separation of the chloroform, gelsemine may be identified by means of the reaction with nitric acid, and also the reaction with potassic bichromate and sulphuric acid.
5. COCAINE.
§ 413. Cocaine (C17H21NO4).—There are two cocaines—the one rotating a ray of polarised light to the left, the other to the right. The left cocaine is contained in the leaves of Erythroxylon coca with other alkaloids, and is in commerce.
Cocaine has been used most extensively in medicine since the year 1884—its chief use being as a local anæsthetic. Chemically cocaine is a derivative of ecgonin, being ecgonin-methyl-ester. It has a pyridine nucleus, and may be written C5H4N(CH3)—H3CHO—(COC6H5)—CH2COOCH3, or expressed graphically as follows:—
Properties.—Cocaine is in the form of four- to six-sided prisms of the monoclinic system. It is one of the few alkaloids which melt under the temperature of boiling water, the melting-point being as low as 85° in water. It readily furnishes a sublimate at 100°, partially decomposing. On boiling with hydrochloric acid cocaine is decomposed into methyl alcohol, ecgonin, and benzoic acid, according to the following reaction:—
| Cocaine. | Benzoic acid. | Ecgonin. | Alcohol. | |||||
| C17H21NO4 | + | 2H2O | = | C6H5COOH | + | C9H15NO3 | + | CH3OH. |
Cocaine is but little soluble in water, but easily dissolves in ether, alcohol, benzene, chloroform, and carbon disulphide; an aqueous solution is alkaline to methyl-orange, but not to phenol-phthalein. It can be made synthetically by the reaction of ecgonin-methyl-ester with benzoyl chloride.
§ 414. Cocaine Hydrochlorate (C17H21NO4HCl).—Crystallised from alcohol, cocaine hydrochlorate appears in prismatic crystals; these crystals, according to Hesse,[463] when perfectly pure, should melt at 186°, although the melting-point is generally given as 200° or even 202°. Cocaine hydrochlorate is soluble in half its weight of water, insoluble in dry ether, but readily soluble in alcohol, amyl alcohol, or chloroform.