OF THE VAPOURS OF BENZENE AND ITS IIOMOLOGUES. 
519 
correspond more closely with those under which the solutions were examined. The 
following; tabulated statement will render this evident :— 
Heads of bands .... 
I. 
II. 
III. 
IV. 
V. 
VI. 
A. 
A. 
A. 
A. 
A. 
A. 
Solution spectrum . 
2681 
2599 
2541 
2483 
2429 
2376 
Vapour spectra :—- 
(1) Grebe. 
2665 
2587 
2526 
2463 
2412 
2360 
Differences. 
16 
12 
15 
20 
17 
16 
(2) At 12° • 7 C. and 759 ■ 5 mm. bar. 
2670 
2589 
2528 
2469 
2416 
2365 
Differences. 
11 
10 
13 
14 
13 
11 
(3) At 11° - 5 C. and 778 mm. bar. 
2669 
2591 
2527 
2470 
2413 
— 
Differences . 
12 
8 
14 
13 
16 
— 
The measurements taken from vapour spectrum { 3), at I l°‘5 C. and 778 mm. bar., 
show the absorption to have so greatly increased that Band VI. has entirely 
disappeared. 
The difference between the solution spectrum and the vapour spectrum at 12°7 C. 
and 759'5 mm. bar. is that the former is shifted from 10 to 14 Angstrom Units in the 
direction of the less refrangible rays. 
On the photograph fig. 4, it will be seen that both the solution bands and the 
groups of vapour bands fade away in the direction of the visible rays. Owing to the 
weakness of the continuous rays beyond X 2329, which is partly caused by the 
general absorption exerted by the benzene thereabouts, it is desirable that those 
bands which clearly appear on the original photograph fig. 4 should be recorded 
because the printing process does not reproduce them. There are also bands which 
become too indistinct under the magnifying power used to admit of their being 
accurately measured with the micrometer, although quite visible under ordinary 
inspection. 
Vapour Bands. —One band is seen at A 2200, and several near XX 2194 and 2234. 
One band at least is visible between XX 2265 and 2238. Two bands about X 2300, one 
of these is at 2279. One band is seen at X 2326, and another between XX 2321 and 
2318. There are several very definite bands about X 2700. These are all in addition 
to those of which measurements have been already recorded. 
Solution Baruls. —The general absorption caused by the benzene solution is so 
intense as to completely obliterate the strong cadmium lines XX 2194, 2144, and 2114, 
and also the continuous rays which otherwise are seen to occupy the spaces between 
them. Three bands occur with heads at XX 2600, 2616’5, and 2642, and another, 
commencing at X 2682, extends towards the less refrangible rays. 
Between the vapour spectra (2) and (3) there is an important difference due to the 
