568 
Mr Purvis, The absorption spectra 
The absorption spectra of some compounds of pyridine. (Third 
paper.) By J. E. Purvis, M.A., St John’s College. 
[. Received 18 May 1908.] 
The absorption spectra of various compounds of pyridine and 
collidine have been already studied by the author and Foster 
( Proc . Garnb. Phil. Soc. vol. xiv. pt. iv. p. 381 and pt. V. p. 435). 
It was proved that the persistence of the absorption band of various 
chlorine derivatives increased according to the number of chlorine 
atoms introduced into the nucleus, and that on loading the ring 
by increasing the number of chlorine atoms, the band was shifted 
towards the red end. The observations confirmed the previous 
observations of other compounds of pyridine by Baker and Baly 
(, Journ . Chem. Soc. vols. 91 and 92, pp. 1122 — 1132). 
It was further shown that when the chlorine atoms were 
introduced into the side chains, as in 9-chlorocollidine, the 
increased number of atoms did not increase the persistence of 
the band, but decreased it a little less than that of the collidine 
band, although there was a considerable shift of the band towards 
the red end. 
Also, with regard to a compound called 7-chlorolutidine which 
had been obtained from 9-chlorocollidine, the increased persistence 
of the band indicated the great probability that six of the chlorine 
atoms had replaced the six hydrogen atoms of the side chains, 
whilst the remaining atom had entered the nucleus. 
In Baker and Baly’s investigations ( loc . cit.) it is stated that 
the shifts of the bands of the isomeric compounds of picoline were 
different and that, expressed in oscillation frequencies, they were : 
a-picoline, 3875, 
/3-picoline, 3800. 
Baly and Collie {Journ. Chem. Soc. 1905, p. 1332) have also 
pointed out that the introduction of a single group modifies the 
absorption spectrum of benzene, different types of absorption being 
produced according to the nature of the group introduced. 
And Baly and Ewbank {Journ. Chem. Soc. 1905, p. 1355), in 
the case of disubstituted derivatives of benzene, have proved that 
