ISSG.] KEW YORK ACADEMY OF SCIENCES. 195- 



cently acquired new interest; one of its constituents, pyridine 

 (O^H^N), has been obtained in several ways, which show that it 

 bears the same relation to certain acids derived from natural 

 alkaloids, such as quinine, nicotine, etc., that benzene does to 

 benzoic and phthalic acids. These facts point to the possible arti- 

 ficial preparation of quinine at no distant day. This view of tlie 

 constitution of tlie alkaloids is confirmed in many ways, notably 

 by Ladcnburg's discovery that piperidine, a base occurring in 

 pepper, is hexahydrobenzene.°^ 



The discovery, by Victor Meyer,^^ of thiophene, a constituent 

 of coal-tar benzene, having sulphur in its composition, is of more 

 than passing interest. Meyer assigns to thiophene a structural 

 formula, which shows itsanalogy to furfuran and to pyrrol. Tiiis 

 is indicated in the following gi'aphic formula3: 



II H H H H H 



\ / \ / \ / 



C-C C-C C-C 



H-C C-H H-C C-H H-C C-H 



\ / \ / \ / 



SON 



I 



H 

 Thiophene. Furfuran. Pyrrol. 



(19.) Professional chemists note with interest the important 

 avenues of research opened up by the extension of the so- 

 called ring structure of carbon compounds, and by the intro- 

 duction of elements other than carbon into the closed chain of 

 atoms. The demonstration by Kekule, in 1805, that benzene 

 contains a group of carbon atoms joined in such way as to form a 

 regular hexagon, has wonderfully advanced our knowledge of the 

 complex bodies in the aromatic series. 



Numerous bodies are now known whose structure is expressed 

 by closed chains of three, four, five, and six links. Dewar " 

 was the first, we believe, to show that nitrogen can replace one 

 of the carbon atoms of a six-link chain in pyridine, and Hof- 

 mann " has shown that three atoms of nitrogen and three of car- 

 bon unite to form a closed chain in melamine : 



