FOOD-COLORING SUBSTANCES. 
53 
and 1 cc of 20 per cent ammonium chlorid solution, and is heated in 
a test tube in a boiling water bath for from five to eight minutes. It 
is then quickly cooled. The reactions obtained with certain dyes are 
shown in the table. The test requires some care, and blanks with 
known dyes should be carried through at the same time in all cases. 
The results with a number of common azo dyes are shown in 
Table 6, the derivatives of 2-naphthol-3-6-disulphonic acid forming 
new dyes of markedly different solubilities, corresponding to the fact 
that they contain one less sulphonic acid group. By warming with 
the cyanid solution for a considerable period of time further reac- 
tions easily take place, derivatives of 2-naphthol-3-6-disulphonic 
acid and 2-naphthol-6-8-disulphonic acid being especially unstable. 
The common nitro dyes are changed by warming with cyanid 
solution, becoming brownish or reddish (compare formation of iso- 
purpuric acid from trinitrophenol) . 
Table 6. — Behavior of colors vnth cyanid solution. 
Dye. 
"Second component" of dye. 
Behavior with cyanid solution. 
108 
Azorubin 
S.G. 
106 
107 
Naphthol trisulphonic acid 
(2-3-6-8). 
Naphthol disulphonic acid 
(2-6-8). 
Naphthol disulphonic acid 
(2-3-6). 
Naphthol disulphonic acid 
(2-6-8). 
Naphthol disulphonic acid 
(2-3-6). 
Dioxynaphthalene 
disulphonic acid (1-8-3-6). 
Aminonaphthol disulphonic 
acid (1-8-3-6). 
Naphthol disulphonic acid 
(1-4-8). 
Naphthol disulphonic acid 
(1-3-6). 
Naphthol disulphonic acid 
(2-3-6). 
Naphthol disulphonic acid 
(2-3-6). 
Naphthol disulphonic acid 
(1-3-6). 
Naphthol disulphonic acid 
(2-6-8). 
Naphthol disulphonic acid 
(2-3-6). 
Warmed 8 minutes, dye almost completely destroyed with 
production of orange and yellow substances. Warmed 
until dark red (1-2 minutes), strongly acidified, and washed 
with 2 N HC1, practically no color is removed (3-4 wash- 
ings); then washed with N/4 HC1, a bluish red dye is readily 
removed. 
Apparently unchanged by cyanid. 
Dye is not changed in solubility, although on long warming 
much color is destroyed. The cyanid mixture may be 
acidified with 5 cc concentrated hydrochloric acid, and 
shaken out with 10 cc of amyl alcohol. On separating the 
alcohol, and washing 4 or 5 times with fourth-normal hydro- 
chloric acid, nearly all of the dye will be taken out by the 
dilute acid. 
Dye is changed into a cyan-derivative similar in solubility to 
other disulphonated monazo dyes. The cyanid mixture 
is pale brown and when treated as stated under New 
Coccin (106), almost all coloring matter remains in the 
amyl alcohol. On long heating of the cyanid mixture the 
cyan-derivative may be completely destroyed, further re- 
actions taking place. 
Dye unchanged. Cyanid mixture, when acidified with 1 cc 
glacial acetic acid and shaken with 5 to 10 cc amyl alcohol, 
gives up little coloring matter to the latter. 
Dye changed into a cyan-derivative similar in solubility to 
the other monosulphonated monazo dyes. The cyanid 
mixture is pale brownish, and when treated as described 
under Orange G (14) gives up most of its coloring matter 
to the alcohol. 
As stated for 14. 
As stated for 14. 
As stated for 14. 
As stated for 14. 
As stated for 15. 
As stated for 15. 
As stated for 14. 
As stated for 14. 
As stated for 15. 
