ABSORPTION SPECTRA AND CHEMICAL CONSTITUTION. 325 
One of the most interesting points in this work of Russell and 
Lapraik is the observations on substituted benzenes and ammonias : for 
every CH; group introduced either into the C,H, or the NH, molecule 
there is a shifting of the bands of absorption towards the red end of the 
spectrum. This is quite definitely established. In the ultra-violet a 
similar result was found by Hartley and Huntington for tri-ethylamine, 
di-ethylamine and ethylamine : for each ethyl group introduced there was 
a shortening of the spectrum. ! 
On THE INFLUENCE OF THE ATomIc GROUPING IN THE MOLECULES oF 
OrGANIC BoDIEs ON THEIR ABSORPTION IN THE INFRA-RED REGIoNn 
or THE Spectrum.” By Captain Abney, R.Z., F.RS., and Lieutenant- 
Colonel Frstine, &.Z. 
Abney and Festing have photographed rays extending down to 
A 12000 ; the visible region ends about \ 7600. They studied the absorp- 
tion spectra of water, hydrochloric acid, chloroform, carbon tetra- 
chloride, cyanogen, and a number of hydrocarbons and their hydroxyl, 
haloid, and carboxy] derivatives, 
Those carbon compounds which contain hydrogen show a character- 
istic group of lines, which, however, are absent from compounds contain- 
ing no hydrogen. They do not all appear in some of the hydrogen 
compounds, and it is inferred that they belong to hydrogen. 
When oxygen is present as hydroxyl, it obliterates the rays between 
two of the lines, which are due to hydrogen. When it forms part of the 
carbon nucieus of a compound, as it does in aldehyde, the spectrum is 
inclined to be linear, or the bands are bounded by well-defined lines. 
These appear to be characteristic bands which indicate the carbon nucleus 
of a series of substances. 
There are some radicals which exhibit a distinctive absorption spec- 
trum, in some cases lying near 7000, in others about 9000. In 
benzene, aniline, and ethylaniline, the following coincident bands are 
probably due to the benzene nucleus ; a line at \ 8670 is the principal one, 
A 8670 to 8720, \ 8720 to 8880, and a fourth band about \ 9300, a fifth 
being about \ 10400 to 10660. 
In benzene and ethyl-aniline there occurs a band also at \ 10970 to 
11050. If the line \ 8670 is associated with a band, it is almost certain 
to be caused by the benzene nucleus. 
Ethyl compounds are indicated by absorption at \ 7410, 8950 to 9030, 
9040 to 9070, 9130 to 9180, 9270 to 9300-5, and 9320 to 9420, 
It is remarkable that the solar spectrum shows an absorption band 
at \ 8660, and, with the exception of the line at 7410, the absorptions 
observed are coincident with bands or lines in the solar spectrum. 
It is also a remarkable fact that the halogens are not recognisable 
by any band or lines; for instance, the lines of hydrochloric acid are 
really the lines of hydrogen. 
1 Phil. Trans. 1879, Plate 22, 
® Phil. Trans. Part III, 1881, by Captain Abney, R.E., F.R.S., and Lieut.-Col. 
Festing, R.E. 
