ORGANIC ACIDS AND THEIR SALTS 99 



tobacco arc probably ascribable to nicotine. In the impure 

 form it is used as an insecticide. 



(/) Quinine, C20H24O2N2, is usually a white, amorphous 

 powder, although it can be obtained in silky needles, and has 

 a very bitter taste. It is used in medicine as the sulphate, 

 (CsoHuQJTiVHsSOi, being particularly efficacious in malaria, 

 and as a tonic and stimulant. 



(g) Strychnine, C21H22O2N2, is a white crystalline powder, 

 with very bitter taste, and is a powerful poison. It is used 

 in medicine in very small doses as a nerve stimulant. Anti- 

 dotes are potassium permanganate, emetics, and sedatives. 



(/?) Theobromine, C7H8O2N4, is a white crystalline powder 

 of bitter taste. It is the active principle of chocolate and 

 cocoa, occurring to the extent of about 1 per cent, in the 

 cocoa bean. It is used medicinally to some extent, its effect 

 being similar to that of caffeine. 



V. ORGANIC ACIDS AND THEIR SALTS 



87. General. — In discussing the various plant compounds, 

 it has been found that there are a large number of organic 

 acids present in one form or another. The fixed oils (Section 

 63) are glyceryl salts of various fatty acids of high molecular 

 weight; some of the volatile oils (Section 75) are esters of 

 organic acids both of the chain and carbocyclic series; 

 some of the resins (Section 77) are composed largely of very 

 complex acids or their salts; alkaloids (Section 85) exist in 

 combination with organic acids of various kinds. But in 

 none of these cases do the acids display the properties which 

 are usually ascribed to them, namely, that of a sour taste 

 and distinctly acid reaction. There are, however, in main' 

 plants, chiefly in the fruits, acids which respond to these 

 tests. As mentioned in Section 28, acids may be in part at 

 least the products of imperfect oxidation, or intermolecular 

 respiration. They may be in part waste products (compare 

 oxalic acid below), or they may serve some definite, physio- 

 logical function. 



