348 REPORT—1899. 
Rosaniline hydrochloride, 
HN GBD G/7 
HAN - OH, /\, 
NH - HCl 
| 2,0 
C,H, : CH; 
Tn this substance the absorption is greater than in rosaniline, all rays 
beyond C and between B and C ('/A 1500) are absorbed. 355th of a 
milligram molecule absorbs all rays beyond !/\ 1600 between B and C. 
yosoth absorbs all from !/\ 1600 to near H or !/\ 2500; while 55th 
transmits all rays to !/A 4600. 
Trimethylrosaniline hydrochloride hie Violet). 
He \G .H,- CH, 
The introduction of the methyl groups increases the opacity of the 
liquid ; it begins to transmit red rays with little more than ;,1,,th of a 
milligram molecule ; with .,J,,th it transmits from 1/\ 1500 near C to 
1/X 2500 near H, and absorbs all beyond. With 5,,th of a molecule it 
transmits rays between G and H, while .,;th transmits all to 1/A 
4400. 
Trimethyl-rosaniline di-methyl-di-codide (Iodine Green), 
N-CH, 
| CHI 
C,H, ‘ CH 
OH, HN et hat 
CH, ‘HN - 0,H,/\ 
The addition of two methyl iodides to the molecule of trimethylros- 
aniline causes complete absorption of rays as far down as 1/X 1350. 
z95oth of a molecule transmits ae between !/A 1350 and 1390; the 
absorption then continues to F (1/A 2050). Rays are transmitted “from 
11) 2050 to 1/A 2200; absorption occurs again to near N ('/A 2780) 
and transmission to near O (!/A 2890). With /,,th of a molecule all 
rays are transmitted to 1/A 4600. 
On carefully comparing the curves of the rosaniline series of dyes 
with triphenyl-methane and benzene, it is seen that they are modifications 
of the benzene curve. All these curves aredrawn to scale. The closeness 
of relationship of the triphenyl-methane curve to the dyes is much greater 
than that of the benzene curve, und the curves of the three dyes are 
modified in such a manner that they follow each other closely. The 
modification is such that the molecules of greatest mass transmit the least 
light, and the light is composed of rays vibrating with least rapidity, thus 
indicating, in the case of the dyes, a greater amplitude and less rapidity 
of vibration than that of the molecule of triphenyl-methane, while the 
difference in this respect between this substance and benzene is extra- 
ordinary. 
Azobenzene, C;H;* N : N : O,H;. 
ith of a milligram molecule of azobenzene transmits the visible rays as 
far as a point lying between C and D, or !/\ 1625; ;1,th of a molecule 
transmits to between E and F, or '/A 1970; 54,th of a molecule trans- 
mits to between E and F, or !/A 2020 ; then occurs an absorption as far 
as M, or 1/A 2690. ¢},th of a molecule transmits to just beyond F, or 
1/\ 2090 ; then occurs an absorption to between G and H, or !/A 2470. 
