22 



ATLAS OF ABSORPTION SPECTRA. 



8. Aurantia Continued. 



at 0.4I/A. As the concentration in- 

 creases the absorption encroaches 

 much faster on the transparent re- 

 gion in the ultra-violet than on the 

 limit in the yellow. Very trans- 

 parent to yellow and orange. 



9. Fast Yellow. (B.) Sodium salt of 



amidoazotoluene-disulphonic acid. 



Somewhat similar to fig. 40, pi. 10; 

 No. 9, S. & J. 



Brownish-yellow powder. In solution 

 brownish yellow, yellow. 



15 g. per liter. 



Angle 23.4'. Depth o to 0.21 mm. 



Absorption in violet and blue. The 

 region of partial transmission in 

 the ultra-violet is not as complete 

 for solution No. 9 as for solution 

 No. 32. Also the boundaries of the 

 violet band are somewhat more defi- 

 nite for the former solution than 

 for the latter. The less refrangible 

 side of this band is more like the 

 corresponding region for solution 

 No. 129, fig. 13, pi. 3. Absorption 

 decreases gradually from o.20/i, to 

 semi-transparency at about 0.34/1. A 

 wide, diiifuse band extends from this 

 region to about 0.475/*. Its maxi- 

 mum is at 0.40/1. Transparent from 

 o.475/t to 0.63/*. 

 10. Orange G. (A.) Sodium salt of benzene- 

 azo-jff-naphthol-disulphonic acid G. 



Fig. 30, pi. 8; No. 14, S. & J. 



Yellowish-red powder. In solution 

 red, yellow. 



Saturated (heated). 



Angle 21.3'. Depth o to 0.18 mm. 



Strong absorption in blue and green. 

 Sharp on yellow edge. Two ultra- 

 violet bands meet at about 0.29/* in 

 a semi-transparent spot. The maxi- 

 mum of the less refrangible band is 

 0.325/t. This strong band meets a 

 very weak one at 0.365/*. The center 

 of the weak band is 0.39/t. The 

 weak band joins an intense one at 

 o.42/<,. This last band joins a still 

 stronger band, from which it is not 

 resolved, at 0.485/1. The maximum 

 of the stronger band is at 0.505/1. 

 Absorption ceases at 0.53/t. Com- 

 plete transparency to 0.63/t. 



II. Ponceau 2 G. (M.) Sodium salt of 

 benzene -azo-/?-naphthol - disulphonic 

 acid R. 



11. Ponceau 2 G Continued. 



Fig. 6, pi. 2; No. 15, S. & J. 



Bright-red powder. In solution yel- 

 lowish red, yellow. 



7 g. per liter (filtered). 



Angle 27.3'. Depth o to 0.25 mm. 



Comparatively weak band in the blue- 

 green, with a shadowy, fainter com- 

 panion on the yellow side. Absorp- 

 tion decreases gradually from o.20/t 

 to 0.34/1. The nearly transparent 

 region from 0.34/1 to 0.44/* is inter- 

 rupted by a very faint band having 

 its maximum at 0.39/1. The pair of 

 stronger bands extends from 0.44/1 

 to 0.545/1. Transparent from 0.545/1 

 to 0.63/1. Same empirical formula 

 as No. 10. No. 10 is derived from 

 the G acid, while No. 11 is a salt 

 of the R acid. 



12. Chrysoidine. Hydrochloride of diami- 



doazobenzene. 



Fig. 7, pi. 2 ; No. 17, S. & J. 



Reddish-brown powder. In solution 

 brown, yellow. 



10 g. per liter (filtered). 



Angle 23.4'. Depth o to 0.21 mm. 



Absorption in violet, blue, and green 

 with maximum in the indigo. Ab- 

 sorption decreases from 0.20/1 to 

 0.33/t. Transparent from 0.33/t to 

 0.36/1. A pair of broad, unseparated 

 bands absorbs from 0.36/1 to 0.54/t. 

 The band of greater refrangibility 

 is the more intense and has its max- 

 imum at 0.43/t. Transparent from 

 0.54/1 to 0.63/1. The less refrangible 

 band disappears first on dilution. A 

 five-strip negative shows that the 

 outer boundaries of the pair of bands 

 are steep and definite. 

 13. Chromotrope 6 B. (M.) Sodium salt 

 of />-acetamidobenzene-azo- 1 :8-dioxy- 

 naphthalene disulphonic acid. 



Fig. 8, pi. 2; No. 38, S. & J. 



Grayish-brown powder. In solution 

 red, pink. 



5.71 g. per liter. 



Angle II. 7'. Depth o to o.ii mm. 



Strong absorption in green-yellow. 

 Transparent from 0.35/1 to 0.465/t. 

 A strong band has its beginning at 

 0.465/i and its maximum at 0.515/t. 

 The less refrangible side joins a weak 

 companion band extending into the 

 orange and red. More dilute solu- 

 tions show that the intense band is 

 symmetrical with respect to its max- 



