CHELIDONIC ACID. 431 



carbonic anhydride and comenic acid, C 6 H 4 5 , which 

 consists of very hard and difficultly soluble granules. 

 Comenic acid, in its turn, yields by distillation another, 

 easily fusible, monobasic acid, subliming in shiny 

 laminae, pyrocomenic acid, C 5 H 4 3 . 



6. Chelidonic acid, C 7 H 4 6 . In Chelidonium majus, 

 particularly at the blossoming period of the plant. 

 The expressed, boiled, and filtered juice is acidified 

 with nitric acid ; and lead chelidonate precipitated with 

 lead nitrate. This, when decomposed with sulphuretted 

 hydrogen, yields impure chelidonic acid, which is 

 purified by preparation of salts, and recrystallization. 

 Long, shiny needles. Difficultly soluble in cold water 

 and alcohol, more easily yi hot water ; not volatile 

 without decomposition. Strong acid ; dissolves iron and 

 zinc with evolution of hydrogen. Tribasic. Treated 

 with bromine and water it is decomposed, forming 

 bromoform, pentabromacetone (C 3 HBr*0), and oxalic 

 acid. 



B. BASES (ALKALOIDS). 



In a large number of plants occur peculiar nitrogen- 

 ized bases, combined with acids. Although present in 

 but very small quantity, they form, as a rule, the active 

 principle of these plants, which are mostly distin- 

 guished for poisonous or healing properties. 



The majority of these bases are crystallizable and 

 not volatile ; only a few are liquid and distillable. 

 Nearly all of them are sparingly soluble in water, 

 easily soluble in alcohol, turn litmus-paper blue, and 

 have a bitter taste. 



Their preparation takes place usually in the follow- 

 ing manner : the proper portions of the plants are ex- 

 hausted with water or dilute hydrochloric acid, and 

 the bases (if volatile) separated by distilling with an 

 alkali, or (if not volatile) precipitated by means of a 

 stronger, inorganic base. As in the latter case, how- 

 ever, a number of other substances are precipitated at 



