ABSORPTION SPECTRA OF THE ALKALOIDS. 
515 
It has been shown by the researches of Dr. C. R. A. Wright that the aconitines 
all yield apo-derivatives with such facility that to obtain the bases free therefrom is 
not an easy matter, and further they undergo saponification by acids and alkalies, 
very readily yielding an inert base in each case. Hence different preparations yield 
different absorption curves. The aconitine and japaconitine of Dr. Wright have 
practically the same absorption spectrum and yield similar curves, but that of 
japaconitine is just what we might expect from a body with a nucleus of a similar 
constitution but twice the molecular weight of aconitine, namely, a much greater 
absorptive power. It has been shown that japaconitine has such a difference, for it is 
in fact a sesqui -apo-aconitine.* 
The English aconitine of Messrs. T. and H. Smith and Co. appears to be a modified 
form of japaconitine, and it is possible that the modification of the spectrum curve is 
in part due to an admixture of another body. 
Foreign aconitine is doubtless an entirely different substance, since it yields no 
absorption bands, and it is known to be comparatively inactive physiologically. 
On two separate occasions it was found necessary to estimate the strength of 
solutions of aconitine, and this was in each case successfully accomplished by taking a 
series of photographs and constructing a curve therefrom. That the results so 
obtained were correct was proved by a discovery of some missing notes giving 
particulars of the preparation of the solutions; 
The constitution of the cinchona bases. 
The examination of these bases was made by me five years ago, and although there 
were no means of obtaining accurate measurements of wave-lengths of the absorbed 
rays at that time, owing to the requisite data being wanting, yet some idea of the 
constitution of quinine and cinchonine was derived from a comparison of the absorp¬ 
tion bands seen in the spectra of the substances themselves and of their derivatives 
and decomposition products. 
The bands in the case of quinine and cinchonine extend into a region of less 
refrangibility than the absorption caused by pyridine, at the same time the position 
of the band agrees with that of quinoline. 
In one of a series of papers contributed to the ‘ Transactions of the Chemical 
Society,’ vol. xli., p. 45 (“ Researches on the Relation of the Molecular Structure of 
Carbon Compounds to their Absorption Spectra.”—Part VI.), I remarked that the 
quinine spectrum was probably due to the conjugation of four pyridine or two 
quinoline nuclei. Since then, several researches on the cinchona alkaloids have 
extended our knowledge, and formulae have been proposed for quinine and for 
* Vide the structural formulae in the papers by Weight and Luff, and Wright and Menke, J. Chem. 
Soc., vol. xxxiii., p. 173 ; vol. xxxv., p. 404. 
