386 CONSIDERATION OF CARBON COMPOUNDS. 



in alcohol and ether, and it is this latter property which is made use of in testing 

 sugar (or other substances insoluble in ether) for saccharine. The substances 

 are treated with ether, which is filtered off and evaporated, when the saccharine 

 may be recognized by its taste in the remaining residue. 



Pyrrole, C 4 H 5 N. During the destructive distillation of certain 

 nitrogenous matters (chiefly bones), a liquid known as bone-oil is ob- 

 tained, which contains a number of nitrogenous basic substances, 

 among which pyridineand pyrrole are found. Pyrrole has but weak 

 basic properties, is insoluble in water and has an odor like chloroform. 



A solution of pyrrole in alcohol, treated with iodine in the presence 

 of oxidizing agents, such as ferric chloride, deposits after some time 

 crystals of tetra-iodo pyrrole, C 4 HI 4 N. This compound is used under 

 the name of iodol. It is a pale-yellow, crystalline powder, almost 

 insoluble in water, soluble in 3 parts of alcohol, 1 part of ether, and 

 15 parts of fatty oils; it is, when pure, tasteless and odorless, and 

 contains of iodine 88.97 per cent. 



Pyridine, C 5 H 5 N. This substance has been mentioned above as 

 being a constituent of bone-oil. Other substances have been isolated 

 from this oil and have been found to form a homologous series : 



Pyridine, C 5 H 5 N Lutidine, C 7 H 9 N 



Picoline, C 6 H 7 N Colliding C 8 H U N 



Pyridine is of special interest, because it has been found that several 

 of the alkaloids, such as quinine, cinchonine, etc., when oxidized, 

 yield acids containing nitrogen, which bear to pyridine the same 

 relation that benzoic acid bears to benzene, or that acetic acid bears 

 to methane. 



Thus, when nicotine is treated with oxidizing agents, nicotinic acid, 

 C 6 H 5 NO 2 , is obtained, which, when distilled with lime, breaks up 

 into pyridine and carbon dioxide, thus : 



C 6 H 5 N0 2 : C 5 H 5 N + C0 2 . 



The relation of nicotinic acid to pyridine, of benzoic acid to ben- 

 zene, acetic acid to methane, may be shown thus : 



CH 3 .H C 6 H 5 .H C 5 H 4 N.H 



Methane. Benzene. Pyridine. 



CH 3 .C0 2 H C 6 H 5 .C0 2 H C 6 H 4 N.CO 2 H. 



Acetic acid. Benzoic acid. Nicotinic acid. 



Pyridine is also obtained together with another basic substance, 

 termed quinoline, C 9 H 7 N, by distilling quinine or cinchonine with 

 potash. These observations, showing an intimate relationship between 



