486 
DR WALTER NOEL HARTLEY ON THE ABSORPTION SPECTRA 
is continuous to about X 2340. The three lines Cd XX 2329, 2318*8, and 2288 are 
feebly transmitted. 
At 100° C.—There is a sharp abrupt absorption commencing at X 2748, which is 
complete until the group of lines XX 2329 to 2265 is reached, and these are 
transmitted. 
At 72° C.—The same absorption occurs, but is not abrupt and not so intense. The 
rays are feebly transmitted near XX 2748, 2575, and as far as X 2329. 
At 45° C.—There is a complete, but feeble, transmission of all rays as far as XX 2329, 
2234-9. 
At 20° C.—The same, but stronger, extending to X 2194*7, which is feeble. A 
feeble band is seen near X 2700. 
Meta-xylene vapour. (Table XIII., p. 513.) 
At 100° C.—There is almost a complete absorption which is not abrupt, from 
XX 2700 to about 2350. Rays are transmitted from XX 2350 to 2234. 
At 70° C.—The rays are feebly transmitted from XX 2680 to 2234, but a broad and 
weak band extends from XX 2600 to 2500. 
At 40° 0.—The rays are well transmitted to X 21947, but they are crossed by 12 
groups of absorption bands. 
At 11° C.—The rays are well transmitted, but with fewer bands. 
Para-xylene vapour. (Table XIY., p. 514.) 
At 100° C.—The spectrum is transmitted as far as X 2802 ; beyond X 2794 there is 
complete absorption to X 2350. Bands are seen at XX 2802 and 2800. Rays are 
transmitted at X 2288. 
At 70° C.—The same, but the bands are more distinctly visible. 
At 40° C.—The spectrum is transmitted, except where the bands occur, as far as 
X 2334-9. 
At 10° C.—A similar spectrum, with the bands more conspicuous. 
On comparing the spectra of the three xylenes (dimethylbenzenes) with that of 
benzene by inspection of the original photographs, the greatest similarity is seen 
between the meta-xylene and benzene in so far as the grouping of the bands is 
concerned, and the positions in which they are situated. There is also the fact that 
the bands in meta-xylene are well defined, like those of benzene. Some of the bands 
which are apparently common to the two substances are much reduced in width in 
meta-xylene, as, for instance, those at XX 2609 and 2606, and those bands in the 
spectrum of me^a-xylene which lie between XX 2748'7 and 2575 fuse, or merge into one 
