[463] O. Hesse, Annalen, 276, 342-344.
§ 415. Pharmaceutical Preparations.—Cocaine hydrochlorate is officinal. Gelatine discs, weighing 1·31 mgrms. (1⁄50 grain), and each containing 0·33 mgrm. (1⁄200 grain) of the salt are officinal, and used by ophthalmic surgeons. A solution of the hydrochlorate, containing 10 per cent. of cocaine hydrochlorate and (for the purposes of preserving the solution) 0·15 per cent. of salicylic acid is also officinal. Stronger solutions may also be met with; for instance, a 20 per cent. solution in oil of cloves for external application in cases of neuralgia.
§ 416. Separation of Cocaine and Tests.—Cocaine may be shaken out of solutions made slightly alkaline by ammonia by treatment with benzene; it also passes into petroleum ether under the same circumstances. The best method is to extract a solution, made feebly alkaline, thoroughly by ether, and then shake it out by benzene and evaporate the separated benzene at the ordinary air temperature. The property of the alkaloid to melt at or below the temperature of boiling water, and the ready decomposition into benzoic acid and other products, render cocaine easy of identification. If, for instance, a small particle of cocaine is put in a tube, a drop of strong sulphuric acid added and warmed by the water-bath, colourless crystals of benzoic acid sublime along the tube, and an aromatic odour is produced.
Flückiger has recommended the production of benzoate of iron as a useful test both for cocaine and for cocaine hydrochlorate.
One drop of a dilute solution of ferric chloride added to a solution of 20 mgrms. of cocaine hydrochlorate in 2 c.c. of water, gives a yellow fluid, which becomes red on boiling from the production of iron benzoate. This reaction is of little use unless a solution of the same strength of ferric chloride, but to which the substance to be tested has not been added, is boiled at the same time for comparison, because all solutions of ferric chloride deepen in colour on heating.
A solution of the alkaloid evaporated to dryness on the water-bath, after being acidulated with nitric acid, and then a few drops of alcoholic solution of potash or soda added, develops an odour of benzoic ethyl-ester. Cocaine hydrochlorate, when triturated with calomel, blackens by the slightest humidity or by moistening it with alcohol. Cocaine in solution is precipitated by most of the group reagents, but is not affected by mercuric chloride, picric acid, nor potassic bichromate.
Added to the tests above mentioned, there is the physiological action; cocaine dilates the pupil, tastes bitter, and, for the time, arrests sensation; hence the after-effect on the tongue is a sensation of numbness.
§ 417. Symptoms.—A large number of accidents occur each year from the external application of cocaine; few, however, end fatally. Cocaine has thus produced poisonous symptoms when applied to the eye, to the rectum, to the gums, to the urethra, and to various other parts. There have been a few fatal cases, both from its external and internal administration; Mannheim, for example, has collected eleven of such instances.
The action of cocaine is twofold; there is an action on the central and the peripheral nervous system. In small doses cocaine excites the spinal cord and the brain; in large it may produce convulsions and then paralysis. The peripheral action is seen in the numbing of sensation. There is always interference with the accommodation of vision, and dilatation of the pupil. The eyelids are wider apart than normal, and there may be some protrusion of the eyeball.