ESERINE

Powder of Calabar bean, 100 parts; tartaric acid, 1 part; pota ium bicarbonate in powder, q. s.; alcohol (90°) q. s.; rectified and washed ether q. s. Exhaust the bean mixed with tartaric acid by several digestions in alcohol at the heat of a water-bath, alcohol equal to about three times the weight of the powder being used for each maceration. Distil the combined liquors and filter; heat the residue in a water-bath exposed to the air until it contains no more alcohol. After cooling suspend the extract in a small quantity of distilled water, and filter through paper to separate the insoluble resin. Agitate the filtrate with rectified and washed ether, until the ether is no longer sensibly coloured; two or three treatments are usually sufficient. Treat the aqueous liquor which contains the eserine in the state of acid tartrate, with a slight exce of pota ium bicarbonate, until the reaction is alkaline. Shake this liquor several times with ether, which removes the liberated eserine, and deposits it upon evaporation. The product is purified by fresh crystal lisa tions from ether. Pure eserine is colourle or slightly rose coloured; it crystallises in thin lam inæ having a rhomboid form. Most frequently it occurs in commerce under the form of yellowish spangles, or amorphous ma es more or le coloured by the action of the air. It is slightly soluble in water, but di olves freely in alcohol, ether, and chloroform. When a one per cent. solution of it is treated with potash or soda it rapidly acquires a characteristic rose colour. Heated in a flask with a water-bath in contact with exce of ammonia, it gives upon evaporation of the liquor in the open air, a magnificent blue colour, very soluble in the water. This solution treated with acids, produces a very fine dichroic liquor, violet and transparent by transmi ion, and carmine red and turbid by refraction. Eserine has the property of contracting energetically the pupil of the eye. A kilogram of Calabar beans yields on the average one gram of eserine (from ‘Formulæ for new Medicaments, adopted by the Paris Pharmaceutical Society.’) See Calabar Bean .