PROCEEDINGS 
OF THE 
Cmnkitrge 
The absorption spectra of some compounds obtained from pyridine 
and collidine. By J. E. Purvis, M.A., St John’s College. 
[Read 9 March 1908.] 
The absorption spectra described in the following notes were 
obtained by means of the apparatus described by Purvis and Foster 
(. Proc . Gamb. Phil. Soc., Yol. xiv. Pt IV. p. 381), in their investi- 
gations of the spectra of collidine and 9-chlorocollidine. Since 
then, the present writer has continued the study of several com- 
pounds obtained from collidine, together with a substance more 
directly related to pyridine, namely, 3 : 5 dichloropyridine, and the 
aim of this paper is to give an account of the results obtained. 
The absorption curves of 3 : 4 : 5-trichloropyridine, 2 : 3 : 4 : 5- 
tetrachloropyridine, and 5-chloropyridine have been already in- 
vestigated by Baker and Baly (Jonrn. Ghem. Soc. Vols. 91 and 92, 
pp. 1122 — 1132), and they found that the introduction of chlorine 
atoms into the nucleus produced a gradual shift of the band 
towards the red end of the spectrum, and that the persistence 
of the band was greatly increased, according to the number of 
the atoms introduced. 
Dichloropyridine. It follows that dichloropyridine should 
form, as it were, a link in the series, and that the shift of the 
band should be less than that of trichloropyridine, and therefore, 
still less than those of tetra- and pentachloropyridines, whilst its 
persistence should not be so well marked. 
Now, on examining the curve, plotted in exactly the same way 
as before, it is clear that such results have been obtained. On 
comparing it with the curves obtained by Baker and Baly ( loc . cit.) 
of the before-mentioned chlorine derivatives of pyridine, there 
appears to be a shift of the band towards the red end, but it is 
not so marked as in the other chlorine compounds; and, also, the 
persistence of the band is also slightly less than that of the tri- 
chloropyridine, and therefore less than those of the tetra- and 
pentachloropyridines. 
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VOL. XIV. PT. V, 
