52 BULLETIN 448, U. S. DEPAETMEXT OF AGEICULTUBE. 
21.— With sodium nitrite, slightly darker; with alpha-naphthol and sodium carbon- 
ate, dull greenish black. 
318. — With sodium nitrite, paler and redder. 
20°, 93° (480°.— Slowly attacked by nitrous acid); 53°, 55°, 105°, 4°, 706°, 56°, 62° 
64°, 65°, 103°, 139°, 164°, 667°, 169°, 163°, 170°. 
84. — With sodium nitrite, redder. 
146°, 287°, 78°, 710°, 546°, 1°. 
507. — With sodium nitrite, bluer. 
328°, 606°, 154°. 
85. — With sodium nitrite, paler. 
86°, 54°, 13°, 97°, 329°, 139°, 157°. 
95. — Crimson solution becomes yellow with sodiimi nitrite; on addition of hydrazin 
sulphate, red again. 
88. — Crimson solution becomes yellow with sodium nitrite; on addition of hydrazin 
sulphate, red again. 
92°. 
101. — Paler with sodium nitrite. 
102°, 483°, 510°, 26°. 
220, 229.— Slightly paler with sodium nitrite. 
512°, 515°, 516°, 517°, 518°. 520°, 521°, 523°, 2°, 3°, 6°, 534°, 707°, 10°, 468°, 464°, 
438°, 433°, 442°, 476°, 240°, 277° (562°, scarcely attacked; in 50 per cent acetic acid, 
behaves with nitrous acid as with bromin in the bromin test) ; 658°, 496°, 650°, 639° . 
584. — With sodium nitrite, blue; rather rapidly becomes red again on addition of 
hydrazin sulphate. 
448. — Wine-red on diazotization, addition of hydrazin sulphate, alpha-naphthol 
and sodium carbonate; with sodium nitrite in acetic acid solution, first blue, then 
colorless. 
425°, 426°, 451°, 452°. 
427. — Reddish with sodium nitrite. 
197°, 201°. 
17. — With sodium nitrite, paler; after addition of sodium carbonate, naphthol, etc., 
somewhat redder. 
18. — With sodium nitrite, paler; after addition of sodium carbonate, naphthol, etc., 
somewhat redder. 
505°, 499°, 504°, 502°.— May appear bluer when the alcoholic alpha-naphthol 
solution is added. 
16°. — Slowly destroyed by nitrous acid. 
7. — Paler with sodium nitrite; after addition of other reagents, red. 
Aminoazotoluene. — Aa stated above for 7. 
Benzeneazo-/3-naphthylamin, Ortho-tolueneazo-/3-naphthylamin. — These com- 
pounds are almost insoluble in aqueous liquids. As ortho-aminoazo derivatives, they 
are not readily diazotized or coupled. 
REACTIONS WITH POTASSIUM CYANTD. 
With the common monazo dyes, the bromin oxidation will pro- 
vide for an identification of the "first component" of the color, i. e., 
the radical not containing the hydroxyl or amino groups. The other 
radical, usually containing hydroxyl or amino groups ortho to the 
azo junction, is identified with much more difficulty in most cases. 
Since the two ortho-azo dyes permitted in foods are both derived 
from 2-naphthol-3-6-disulphonic acid as second component, the reac- 
tion discovered by Lange * that derivatives of this acid are attacked 
on boihng with potassium cyanid and the 3-sulphonic acid group 
replaced by cyanogen, is useful for distinguishing and separating 
isomeric dyes. 
The test may be made as follows: About 10 cc of the neutral color 
solution is treated with 1 cc of 20 per cent potassium cyanid solution 
i Deutsches Reiehs Patent No. 189,035. 
