126 REPORT— 1903. 



Absorption Spectra and Chemical Constitution of Organic Substances. — 

 Fifth Interim Bsport of the Committee, consisting of Professor 

 W. Noel Hartley [Chairman and Secretary), Professor F. K. 

 Japp, Professor J. J. Dobbie, and Mr. Alexander Lauder, 

 appointed to investigate the Relation between the Absorption Spectra 

 and Chemical Constitution of Organic Substances. 



The work of two of the members of the Committee, Dr. Dobbie and Mr. 

 Lauder, has been exclusively devoted to the investigation of certain alka- 

 loids, and the connection between their chemical constitution and their 

 absorption spectra, and the results they have obtained since the last 

 meeting at Belfast constitute the substance of this report.^ 



Note. — As sometimes the nitrates of the alkaloids are well -crystallised 

 salts, the examination has been in certain cases made with nitrates. It is 

 necessary to observe, however, that unlike chlorides, sulphates, and ace- 

 tates, which are very diactinic and exert only a general absorption, nitric 

 acid and the nitrates give characteristic absorption bands.^ This does not 

 affect the specti-a here referred to, but it might happen that if the effect 

 of the nitric acid were not taken into account, erroneous conclusions could 

 be drawn from the absorption band of the nitric acid being attributed to 

 the organic base. 



In a paper communicated to the Royal Society eighteen years ago by 

 Hartley,^ it was proved that the principal alkaloids give highly characte- 

 ristic absorption spectra which can be used for their identification and for 

 ascertaining their purity. Furthermore, that alkaloids closely related to 

 one another, like quinine and quinidine, cinchonine and cinchonidine, all 

 contained a similar nucleus, which was probably formed by the conjuga- 

 tion of four pyridine or two quinoline groups, and that the opium alka- 

 loids had also a characteristically constituted nucleus which is either a 

 benzene or a pyridine derivative. Tlie effect of alkyl and acetyl sub- 

 stitutions on the curve of absorption was demonstrated, the increased 

 intensity of absorption of the apo- derivatives was shown and accounted 

 for, and the occurrence of several oxidised radicals — hydroxyl, methoxyl, 

 carbonyl, or carboxyl — in the constitution of an alkaloid was shown to 

 be capable of causing remarkable differences in the absorption curves 

 of the original nucleus. At the time a.t which this paper was published, 

 however, little progress had been made with the investigation of the 

 alkaloids, and it was not possible, therefore, to trace any closer connec- 

 tion between their structure and their spectra. In this connection, 

 however, the relationship of the absorption curves to the differences 

 in constitution of quinoline, dihydroquinoline, and tetrahydroquinoline, 

 was determined by Hartley. 



The Absorption Spectra of Corydaline, Berberine, and the Opium Alkaloids. 



The constitution of the principal members of the group of alkaloids to 

 which corydaline and berberine belong — namely, papaverine, hydrastine, 



' Dobbie and Lauder, Chem. Soc. Trans., 190.3, 83, pp. 605, 626. 

 * Hartley, CJievi. Soc. Trans., 1902, 81, and 1903, 83. 

 ' Phil. Trans., 1885, Part II., p. 471. 



