ABSORPTION SPECTRA AND CHEMICAL CONSTITUTION. 329 
in the external ether, so from the wave-lengths of those rays of light 
which are absorbed to the greatest degree by the solution of any sub- 
stance, the number of the vibrations of the molecules within the liquid 
can be calculated from the equation given. The number of vibrations for 
billionths of a second were calculated for indigo, rosolic acid, fluorescein, 
and their various derivatives, the absorption spectra of which had been 
examined. These will be referred to later on. 
The Spectra of Tertiary Bases. 
These substances are of particular interest, owing to their connection 
with the natural alkaloids.’ 
Cinchomeronic acid, the pyridine dicarboxylic acid obtained by the 
oxidation of quinine, &c. with potassium permanganate, has a strong 
absorption band between \ 2743 and d 2574. 
Picoline.—An alcoholic solution containing ;;}5,th of the substance 
shows a strong absorption band lying beyond \ 2743, but a broad band of 
rays is fully transmitted further on. Solutions containing sabuoth show 
a strong absorption band lying between A 2743 and \ 2574. The absorp- 
tion band is narrowed but is not destroyed by dilution to ;p$oq0th. 
Since picoline is a methyl-pyridine it follows that 
The substitution of nitrogen for carbon in the benzene nucleus does 
not destroy or impair the power of selective absorption possessed by the 
original molecule. 
The substitution of nitrogen for carbon in the benzene ring really 
removes an atom of hydrogen. This action greatly increases the absorp- 
-tive power of the substance, as will be seen by comparing methyl-benzene 
(toluene) ? with picoline or methyl-pyridine. There is a striking resem- 
blance between the two spectra, but the narrow band characteristic of the 
homologues of benzene is absent. 
Quinoline.—A solution of this substance in alcohol containing ; >} 59th 
shows one narrow band a little beyond \ 3076. Two narrow bands and a 
broad one are seen in solutions containing ;;1,,5th, and a trace of absorp- 
tion continues until the dilution has reached 55}, 9th. This spectrum is 
a remarkable one. 
Comparing picoline with toluene, and quinoline with naphthalene, the 
chief difference to be noted in their absorption spectra is the increased 
intensity of absorption in the case of the nitrogen compounds. 
Ultra-violet Spectra of Derivatives of the Paraffins. 
By J. L. Soret and A. A. Rinuer.? 
There is considerable difficulty in obtaining compounds of sufficient 
purity for observations on the ultra-violet rays. The alcohols were found 
to show great transparency to the ultra-violet, and any apparent excep- 
tions were probably due to impurities. In the rectification and 
prolonged desiccation of the alcohols there is often slight oxidation, which 
leads to the production of impurities which affect the results of an exami- 
nation. Hartley and Huntington concluded that in the series of alcohols 
1 * Researches on the Relation of the Molecular Structure of Carbon Compounds to 
their Absorption Spectra,’ pt. vi. Trans. Chem. Soc,, February 1882. 
2 Phil. Trans. 1879, Pl. 25. 
8 Comptes Rendus, vol. cx. pp. 137-139, 1890, 
