CODEINE, CODEIN, CODEINA, or CODEIA (Gr. modem, "poppy-head"), a veg etable alkaloid closely allied to morphine and constituting about 0.5 per cent of the weight of opium. Codeine has the formula Ci:Ho (CHO NO.4-H2O, and is known to the chemist as methylmorphine, since it is derived from morphine by substituting methyl (CH,) for one atom of the hydrogen that morphine contains. Codeine may be prepared by adding calcium chloride to an aqueous extract of opium and evaporating to the point of crystallization. The hydrochlorides of morphine and codeine which are obtained in this manner are dissolved in water, and the morphine is precipitated by the addition of ammonia. Codeine hydrochloride remains in solution and may be obtained by evaporation and crystallization, and further purified by recrystallization from ether. Codeine acts as a strong base, and its solution reddens litmus paper, neutralizes acids and precipitates solutions of lead, iron and copper. From aqueous solution it is deposited in the form of tnmetric crystals, as indicated by the formula given above. Crystals free from water may he
obtained by deposition from a solution in car bon disulphide. When treated with strong sul phuric acid and a small quantity of ferric chloride (FeCl,), codeine compounds give an intense blue color. This reaction is of great value in testing for the presence of the alkaloid. Codeine is used in medicine as a narcotic and hypnotic. Its properties are very similar to those of morphine, but by reason of the methyl groups introduced it. has more action on the spinal cord than morphine has. It thus does not cause sleep or relieve pain as readily as morphine, and causes more reflex excitability. It may even cause convulsions in children. It is valuable where a milder sedative than mor phine is desired, as there is less euphoria pro duced and less likelihood of forming a habit Its use is not free from danger, however, and very small doses have been Icnown to prove fatal.