192 



The Absorption Spectra of the Alkaloids. [Mar. 12, 



active aconitines appear to be those with the strongest absorption-bands, 

 and of the commercial samples scarcely two yield the same absorption- 

 spectra. The variations in the curves indicate that not only may there 

 be considerable differences in their composition, but also in their 

 chemical constitution. 



Having prepared some of the tertiary bases in a state of great 

 purity, it was considered desirable to examine the spectra transmitted 

 by pyridine, piperidine, quinoline, tetra-hydro-quinoline, and quinoline 

 hydrochloride. It was found that the addition of six atoms of hydro- 

 gen to pyridine, and four atoms of hydrogen to quinoline, caused the 

 products to become more diactinic. Hex-hydro-pyridine, otherwise 

 piperidine, shows no absorption-band, as was predicted. Quinoline 

 hydrochloride yields a spectrum differing from that of the base. Sub- 

 stitution products are less diactinic than the simple bases. 



As a study of these and similar bodies promises to lead to conclu- 

 sions apart from such as are of importance in this investigation, and 

 of interest in themselves, a detailed account will be reserved for the 

 present. 



The position of the absorption-bands occurring in the spectra 

 transmitted by these tertiary bases may be stated in the following 

 manner : — 



Measurements of 

 absorption-bands- 

 in wave-lengths. 



Pyridine. Band between 2700 and 2300 



With less substance, between. . 2570 and 2400 



Quinoline. 



Two bands (1) { Between 3085 and 3039 



W L With less substance, between. . 3078 and 3039 



, 2 \ f Between 3170 and 2600 



; * L With less substance, between. . 2980 and 2830 

 Tetra-hydro-qtiinoline. 



Two bands (1) / Betwee11 3180 and 2750 



W ° I With less substance, between. . 3180 and 2870 



^ f Between 2700 and 2300 



" \ With less substance, between. . 2650 and 2370 



Quinoline hydrochloride. 



Two bands (1) J Between 3180 and 2750 



I With less substance, between. . 3180 and 2870 



/Between 2700 and 2300 



1 With less substance, between . . 2650 and 2370 



Substances such as any of the natural alkaloids, which may be 

 derived from dihydroquinoline or tetra-hydroquinoline, by replacement 

 of the hydrogens by other elements or radicals, in such a manner as 



