ABSORPTION SPECTRA AND CHEMICAL CONSTITUTION. 300 
these bands, and at the same time to render the lines sharp enough to 
serve as a scale of wave length measurements. 
The series of independent measurements obtained from photographs 
taken under the latter conditions, when compared with those obtained by 
Pauer by examining the vapour of benzene,’ show that his weak line 
d 2670 is identical with the first absorption band, and his weak band 
d 2390-2360 with the sixth absorption band observed in solutions of 
benzene in alcohol. The result of Pauer’s work was to show that the 
constitution of the absorption bands in benzene, when the substance is 
vaporised, is that of lines, or groups of closely adjacent lines. The 
action of a solvent is to cause the lines to be dispersed or merged into 
bands. 
Benzene. 
0-078 gram, or 1 milligram molecule, in 20 c.c. of alcohol. 
Strong absorption bands to the number of six. 
Thickness of 
layer of liquid Description of spectrum + 
in millimetres 
25 One band, absorption beyond complete . 8691—3727 
20 One band. : - : q : ‘ 8691—3727 
10 Two bands, not very distinct. 
First from 3691—3730 
Second from ° ; - : 8755—3883 
5 The first absorption band is barely 
visible. 
The second absorption band from 3802—3854 
Absorption band, third from 8886—3947 
¥ » fourth from 3979—4043 
1 » fifth from 4075—4128 
Pr », sixth from 4170—4189 
4 Absorption band, second from 3802—3847'5 
a » third from . 3883—3947 
Ee s» fourth from 3979—4040 
= » fifth from 4075—4122:5 
3 » sixth from . ‘ i 4170—4215 
5 The description applies to both these 
9 } spectra. | 
Absorption band, second from 3812—3847:'5 
a » third from 3915—3937 
' 4, fourth from 3995—4030 
5 » fifth from 41004120 
* » sixth from 4190—4210 
1 Absorption band, second from 8819— 3847-5 
A » third from . 8915—3934 
4 3» fourth from 4004—4024 
3 » fifth from . - 4103—4116 
i » sixth from . : 2 4202 _4208:5 
Continuous spectrum to 4555 
It is perhaps worth while to draw attention to a slight mistake on 
p. 364 of Herr Pauer’s paper ; he credits Miiller with work on the ultra- 
violet rays, but the author referred to is undoubtedly the late Dr. William 
Allen Miller. It has been explained also by Professor W. R. Dunstan, 
1 Wied, Ane. vol. Ixi, p. 362, 1897. 
