ON THE ATOMIC GROUPING IN ORGANIC BODIES. 
893 
apparatus to a more stable site, a]id till we examined some of the iodides of the alcohol 
series, that we observed many sharply-defined lines and also that the edges of the 
bands were more rigidly marked ; and when it appeared that some of the edges of the 
bands in the compounds containing oxygen were coincident with some of the fine lines 
in the iodides, we were forced to the conclusion that there must be some connexion 
between the one and the other, since such an agreement could not be fortuitous. Our 
endeavour was therefore to discover, if possible, what constituents of the iodides caused 
these lines. They must be due to carbon, iodine, or hydrogen, or to a combination of 
one with the other. 
Our first step was to get a substance which should contain but one atom of carbon 
and one of hydrogen, and this we found in chloroform. On examining the photograph 
of this spectrum we were gratified to find that all bands had disappeared, and that the 
absorption spectra contained only lines, some fine and some broad. By reducing, then, 
the carbon and hydrogen and increasing the halogen a line spectrum was produced. 
It seemed possible, nay, probable, that these lines might be due to the chlorine 
present in such abundance in the chloroform, and if so it was evident that by abstract¬ 
ing the last atom of hydrogen and taking carbon tetrachloride an absorption spectrum 
of a still simpler form, but still lineal, should be obtained. To our surprise, however, 
we found that the absorption of carbon tetrachloride was an absolute blank, and that 
there was no absorption beyond a slight general one at the least refrangible end of the 
infra-red. With carbon disulphide the same negative result was also obtained. 
This seemed to show that neither chlorine nor carbon had anything to do with the 
linear spectrum observed in chloroform. Dr. Hodgkinson kindly prepared for us a 
solution of cyanogen in carbon tetrachloride (180 vols. of gas in one of the solvent), 
and not a trace of line or band was found in its spectrum. A crucial test was to 
observe spectra containing hydrogen and chlorine, hydrogen and oxygen, and hydrogen 
and nitrogen. 
We therefore tried hydrochloric acid and obtained a spectrum containing some few 
lines. Water gave lines, together with bands, two lines being coincident with those in 
the spectrum of hydrochloric acid. 
In ammonia, nitric acid, and sulphuric acid we also obtained sharply-marked lines, 
coincidences in the different spectra being observed, and nearly every line mapped 
found its analogue in the chloroform spectrum, and usually in that of ethyl iodide. 
Benzine again gave a spectrum consisting principally of lines, and these were coinci¬ 
dent with some lines also to be found in chloroform. It seems then that the hydrogen, 
which is common to all these different compounds, must be the cause of the linear 
spectrum. In what manner the hydrogen annihilates the waves of radiation at these 
particular points is a question which is at present, at all events, an open one, but that 
the linear absorptions, common to the hydrocarbons and to those bodies in which 
hydrogen is in combination with other elements such as oxygen and nitrogen, is 
due to hydrogen there can be no manner of doubt. 
