50 
BULLETIN 448, U. S. DEPARTMENT OF AGRICULTURE. 
brownish. With most of the others it is ill-defined and is probably 
often produced by a small fraction of the dye that has escaped 
destruction by bromin. In acid solution these dyes are merely 
destroyed by bromin in most cases, the results being as given for E. 
Class E. — Dyes in this class are similar to those in Class D, but 
show no color changes other than bleaching, on addition of bromin. 
Class F. — Halogenated fluorescein derivatives and similar com- 
pounds. — These dyes are very resistant to bromin. The nonfluo- 
rescent iodin compounds tend to become yellower in shade and to 
develop a green fluorescence, probably due to partial substitution of 
iodin by bromin. 
Table 4. — The bromin test: Classification of colors according to reactions obtained. 
[Numbers denoting permitted dyes are in boldfaced type; natun 
foods are starred, three stars indicating those most often found, 
cent solutions.] 
colors are in italics. Dyes common in 
Statements apply in general to 0.01 per 
Color- 
! 
Color- 
Color- 
Color- 
No. 
ing 
matter. 
Class. 
i 
No. 
ing 
matter. 
Class. 
No. 
ing 
matter. 
Class. 
No. 
ing 
matter. 
Class. 
1 
*462 
D or E. 
33 
56 
A (e). 
65 
*92 
A(w). 
87 
*468 
E. 
2 
434 
D. 
34 
*62 
A A (e). 
66 
101 
A or AA 
88 
464 
E. 
3 
435 
D. 
35 
**64 
AA(e). 
(w). 
89 
438 
D. 
4 
*436 
D. 
36 
*65 
A A (e). 
67 
102 
A(w). 
90 
**433 
D. 
5 
439 
E. 
37 
**103 
A or AA 
68 
483 
E. 
91 
442 
E. 
6 
491 
D or E. 
(w). 
69 
=5=510 
( 3 ) 
92 
476 
E. 
7 
440 
E. 
38 
139 
A or AA 
70 
26 
A(e). 
93 
240 
AJ> 
8 
**602 
E (B).i 
(w). 
71 
220 
A.i 
94 
277 
A. 
9 
*H08 
A (w). 
39 
164 
A(w). 
72 
269 
A.i 
95 
562 
B. 
10 
***8 A (w). 
40 
**667 
B. 
73 
512 
E. 
96 
658 
E. 
11 
9 j A (w). 
41 
*169 
A(w). 
74 
515 
E. 
97 
496 
D orC. 
12 
**89 ' A (w). 
42 
163 
A(w). 
75 
516 
E. 
98 
650 
E or C. 
13 
692 j E. ' 
43 
170 
A(w). 
76 
517 
E. 
99 
639 
EorD. 
14 
399 A (w). 
44 
84 
A(w). 
77 
518 
E. 
100 
*584 
B orC. 
15 
***106 ! A (w). 
45 
146 
A(e). 
78 
520 
E. 
101 
**448 
E or D. 
16 
107 | AA or A | 
46 
287 
A.i 
79 
521 
E. 
102 
***425 
E orC. 
(w). 
47 
78 
A. 2 
80 
*523 
E. 
103 
426 
E or C. 
17 
94 ! A (w). 
48 
***7J0 
E. 
81 
2 
E. 
104 
***451 
EorC. 
18 
*398 | E. 
49 
*546 
B.i 
82 
*3 
E. 
105 
452 
E or C. 
19 
605 1 B. 
50 
1 
E. 
83 
6 
E. 
106 
**427 
D orC. 
20 
604 ! B. 
51 
507 
D. 
84 
534. 
B. 
107 
428 
DorC. 
21 
188 1 A A (w). 
52 
328 
A (w). 
85 
***707 
E. 
108 
*197 
AorC. 
22 
***14 | A (e). 
53 
606 
B. 
86 
no 
A (6).< 
109 
*201 
AorC. 
23 
21 ! A (e). 
54 
154 
A (e). 
110 
17 
A or C (e). 
A or C (e). 
24 
318 A.i 
55 
85 
A(w). 
A (e). 
111 
18 
25 
20 i A (e). 
56 
**13 
112 
505 
D orC. 
26 
93 i A or AA 
57 
***86 
A(w). 
113 
499 
DorC. 
(w). 
58 
97 
A(w). 
114 
***504 
DorC. 
27 
***480 
D. 
59 
54 
A(e). 
115 
502 
DorC. 
28 
*53 
A (e). 
60 
329 
E. 
(<) 
29 
*55 
A(e). 
61 
139 
A (w). 
30 
105 
A (w). 
62 
157 
A(e). 
31 
4 
E. 
63 
*95 
A (w). 
32 
***?06 
E. 
64 
88 
A (w). 
1 Imperfectly. 
2 Some alcohol should be added before- the alpha-naphthol. 
s Gives eosin. 
* Of the oil-soluble dyes given in the other tables all belong to type A except Quinophthalon, which in 
60 per cent acetic acid shows reaction indicated under B. 
5 Very imperfectly. 
REACTIONS WITH NITROUS ACID. 
By treatment with nitrous acid in dilute solution most of the com- 
mon coal-tar dyes used in food coloring are not readily affected. A 
considerable number, however, show marked changes, because of di- 
azotization of free amino groups, of formation of nitroso compounds, 
or of direct oxidation. 
