ABSORPTION SPECTRA AND CHEMICAL CONSTITUTION, JAS 
1888. He was apparently quite unaware that the method of calculating 
the molecular vibrations of a substance had, seven years previously, been 
described in the ‘Journal of the Chemical Society,’ for 1881, and calcu- 
lated for benzene, naphthalene, and anthracene, in a manner identical 
with that which he communicates. This is rendered evident from his 
article on absorption spectra in Graham-Otto’s ‘ Ausfithrliches Lehrbuch 
der Chemie,’ erster Band, pp. 683-694, edited by Dr. H. Landolt in 1898. 
There is an obituary notice of the author by Dr. Hugo Kriiss, stating 
that this contribution was completed in 1889. 
NECESSITY FOR EXAMINING THE ULTRA-VIOLET AND COLOURED 
SPECTRA TOGETHER. 
There is some amount of uncertainty about conclusions drawn from 
observations made on only a part of the spectrum which may be illustrated 
by a glance at the diagram in Hartley and Huntington’s paper, plate 22, 
which is described as that of ortho-nitrophenol, but is in reality the para- 
compound, and that of plate 23, erroneously termed para-nitrophenol, but 
is in reality the ortho-derivative (by accident the plates were transposed). 
In both instances there are two absorption bands, one in the visible 
region or blue, in No. 23, and a second in the ultra-violet. Any reaction 
which will reduce the velocity of the vibrations of the compound will 
shift both bands towards the less refrangible rays. The first band may 
thus be moved into the infra-red region, and the second into the visible 
part of the spectra, say the violet. By observations on the coloured rays 
only, it will be made to appear as if the first band had been moved 
towards the ultra-violet instead of in the opposite direction. 
Another example—an actual case—is afforded by iodine green, 
methyl violet and rosaniline hydrochloride, when compared with triphenyl 
methane. The powerful absorption band of the hydrocarbon is carried 
down into the yellow and green by the influence on the molecule of the 
NH, groups and the chlorine ; the red rays are transmitted, and a por- 
tion of the violet. In the case of methyl violet, the absorption band is 
carried down to a point near C, and it extends to G ; a portion therefore 
of the red is transmitted, and part of the violet. With iodine green the 
absorption band in the less refrangible region extends into the extreme 
limit of visibility in the red, and there is absorption from between A 
and B!/) 1800, until near F !/A 2000 a band of transmitted rays extends 
from 1/ 2000 to 2200, or between F and G. There is then absorption 
in the violet from 1/\ 2200 to 2800 in the ultra-violet, and beyond that 
again there is complete absorption from !/A 2900 to 4000. 
If the visible rays only are observed, and that at one thickness and 
one strength of solution, it might very easily appear that the combined 
effect of NH,, the CH, group, and the I is to cause the band to be 
shifted from the yellow into the violet. Plate I. ‘Chem. Soc, Trans. 
1887, will serve to explain this. It will be well at this juncture to refer 
to the paper more fully. 
Zur Kenniniss der Absorptionsspectra. 
Das Chrysoidin und verwandte Azofarbstoffe.' 
J. Landauer made an examination of the absorption spectra of azo 
dyes. He showed that there was a marked change in the absorption 
1 Ber. vol, xiv. p. 391, 1881, 
