The absorption spectra of collidine, etc. 
381 
The absorption spectra of collidine and 9 -chlor -collidine. By 
J. E. Purvis, M.A., St John’s College, and W. H. Foster, M.A., 
St John’s College. 
{Read 25 November 1907.] 
Among the products of the action of chlorine on collidine, at 
present under investigation by Sell and Foster, there is one of 
special interest, in that it contains nine chlorine atoms in the 
molecule. The investigation by chemical methods appeared to 
show that these nine atoms of chlorine had replaced the hydrogen 
atoms in the three methyl groups of the collidine side chains; 
and it was thought that some additional information might be 
obtained from a spectroscopic examination of the absorption bands. 
Moreover, the very considerable displacement of hydrogen by 
chlorine rendered the body a favourable subject for the study of 
the effect of loading the molecule on the spectrum. The intro- 
duction of nine chlorine atoms means the production of a 
molecule nearly four times as heavy as the original collidine, so 
that we could reasonably expect a considerable shift of the 
absorption band towards the red end of the spectrum. That 
this surmise was correct is proved in the following account of 
the spectroscopic examination of this body compared with that 
of collidine, neither of which has been studied previously. 
The adjustable cell used to contain the solutions was not 
unlike that very useful instrument described by Baly and Desch 
{Jour. Chem. Soc., vol. 85, pp. 1029 — 1041). Their cell consisted 
of two glass tubes with a quartz plate sealed on one end of each 
tube. The outer tube had a broad indiarubber band slipped 
over the junction between the outer and inner tubes to keep it 
water-tight. 
But, in order to avoid the possible action of organic liquids 
on rubber, we had a long brass screw fitted on to the open end 
of the outer tube, and a washer or ring of cotton thread between 
the end of the screw and the screw head itself; so that, on 
screwing up the head, the cotton thread acted as an efficient 
plug, and thereby acted as a stopper to the leakage of any of 
the solution. Besides that, the position of the inner tube was 
made more rigid and firm. 
The iron arc was used as the source of light to pass through 
the absorbing liquids. But it has some disadvantage caused by 
its irregularity and shifting, so that there is some difficulty in 
obtaining a light of regular intensity. In later experiments with 
other substances, we have used the iron spark as the source of 
light. 
