1880.] 



Studies on the Chinoline Series. 



165 



The interest of the subject has been greatly enhanced by the results 

 of Weidel, Schmidt, Ramsay, and Dobbie on the direct oxidation of 

 the cinchona alkaloids. 



All these chemists agree that the chief oxidation product has the 

 composition and properties of either a pyridene di- or tri-carbonic 

 acid. 



My attention being directed to other scientific subjects, I have 

 thought the results of experiments, which I had intended extending, 

 had better be published, as research in this department of organic 

 chemistry is being vigorously prosecuted, which will in all probability 

 at no distant date result in the synthesis of some important alkaloids. 



Oxidation of Cinchona Chinoline. 



Chinoline obtained from cinchonine, which had been carefully 

 purified as described in my former paper, was treated with permanga- 

 nate in the same way as leucoline, in order to see if any acid similar 

 to the leucolinic acid could be obtained. In each operation, about 

 1*3 grms. of chinoline was dissolved in dilute sulphuric acid, and 

 a hot solution of 30 grms. of permanganate of potash added. As the 

 chinoline is more readily attacked than the corresponding tar base, to 

 prevent loss the oxidation must be carried out in large basins, as the 

 mass is apt to froth over from the evolution of carbonic acid. 



After filtration from the oxide of manganese, the alkaline solution 

 was evaporated to dryness, and extracted with alcohol to separate the 

 sulphate, carbonate, and oxalate of potash. 



The soluble potash salt was dissolved in water, excess of sulphuric 

 acid added, and the organic acid extracted by shaking with ether. The 

 yield of acid was small, and as no modification of the process seemed 

 to increase the amount, the substance obtained was chiefly used to 

 determine its composition and general reactions. 



Chinolinic Acid. 



. The acid crystallised in nodular masses very soluble in water. It 

 melts at 143°, or 20° lower than the isomeric leucolinic acid. The 

 silver salt is very insoluble, separating from cold solutions as a floccu- 

 lent precipitate, which on standing becomes crystalline. When it is re- 

 crystallised from a large volume of boiling water, it is obtained in 

 tufts of fine needles. The crystals were always mixed with a slight 

 reddish-brown substance, which appeared to be oxide of silver. 



The acid gave no violet colour with ferric chloride, but the am- 

 monia salt gave a violet precipitate, which rapidly became of a 

 reddish-brown colour. 



Analysis of the acid obtained from cinchona chinoline and the silver 

 salt yielded the following results : — 



