NITROGENOUS COMPOUNDS 97 



for the growth of the plant. They do not occur in all plants, 

 being confined for the most part to the poppy and legume 

 families. They occur as salts of malic, oxalic, succinic, tannic, 

 or some other plant acid, and are extracted by dissolving 

 out these salts with appropriate solvents, and separating 

 the alkaloid from the acid. Ordinarily this is done by using 

 a mineral acid like sulphuric or hydrochloric, since it is in 

 this form that the alkaloids are used commercially; for 

 example, quinine sulphate, cocaine hydrochloride, etc. 



86. Some of the Common Alkaloids. — (a) Atropink, 

 C17H23O3N, is a white crystalline solid with a bitter, acrid 

 taste and is very poisonous. It is used as the sulphate for 

 spasmodic affections, and for dilating the pupil of the eye. 

 Antidotes are emetics, tannin, or charcoal. 



(b) Caffeine or Theine, C 8 Hio0 2 N4, is a white, silky solid 

 with bitter taste. It occurs in tea and coffee in combination 

 with a complex organic acid, the compound being soluble in 

 water and is hence extracted when tea and coffee are treated 

 with water for beverages. The alkaloid, occurring to the 

 extent of 1 per cent, in coffee and 2 per cent, in tea, exerts 

 the stimulating effect of these drinks. In addition, however, 

 there are also extracted tannin (in tea only), volatile oil 

 of tea or of coffee, gum, and dextrin, all of which serve to 

 modify the effect of the alkaloid. Pure caffeine is used 

 in medicine as a stimulant, and to cure somnolence. 



(c) Cocaine, C17H21O4N, is a colorless, crystalline solid 

 with bitter taste, and producing numbness. Used medicin- 

 ally usually as the hydrochloride, C17H21O4N.HCI, it is a local 

 anaesthetic. It is, however, a dangerous drug to use. Anti- 

 dotes are morphine, alcohol, ammonia, and applications of 

 ice to the head. 



(d) Morphine, C17H19O3N, occurs in colorless, shining 

 crystals, with bitter taste, and is used in medicine ordinarily 

 as the sulphate (CnHigOsN^.HoSCX. It is the chief con- 

 stituent of opium which is obtained from the unripe seed 

 capsules of the poppy (Fig. 23). Morphine is one of the 

 most valuable narcotics known, but it is a very dangerous 

 drug to use on account of its habit-forming properties and 

 its general harmful effect on the mind and body when the 



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