PERMITTED COAL-TAR FOOD DYES 7 
of hydrochloric acid to an aqueous solution produces a brown pre- 
cipitate. The addition of sodium hydroxide to an aqueous solution 
turns the color cherry-red. This dye is particularly sensitive to 
traces of alkali and should be used only for neutral or weakly acid 
foods and beverages. It dissolves in concentrated sulphuric acid to 
form a violet-red solution, from which it is precipitated as a red- 
brown mass when diluted with water. 
NAPHTHCL YELLOW S 
Naphthol yellow S (C,.f1,N.0,5Na,), a nitro dye, is the sodium 
salt of 2-4-dinitro-a-naphthol-7-sulphonic acid (15, 25, 34, 87). 
It is prepared by the nitration of ne tri- or disulphonic acids of 
SS sphthol or from the nitroso compound of the 2-7-disulphonic 
acid (24). In any case, care must be taken to guard against the 
production of the unsulphonated subsidiary dye martius yellow, 
which is one of the most poisonous coal-tar dyes known. More 
than a very small trace of martius yellow makes the naphthol yellow 
-$ unsuitable for use in coloring foods. 
Being a nitro compound, naphthol yellow S should be pulverized 
with extreme caution, owing to the danger of explosion. Ex- 
perience has shown that it may be satisfactorily ground and pulver- 
ized in a ball mill. 
Table 5 shows the analytical data which should be incorporated 
in foundation and supplemental affidavits (70) and the methods 
of analysis to be used, and lists the purity specifications for the dye. 
TABLE 5.—Specifications for naphthol yellow S 
“Maximum | 
tolerance | Minimum Method of 
Component (ratio to pure| tolerance analysis 
coal-tar dye) 
Per cent Per cent Page 
LS TIDE ee a ee ee ee ee 10.0 eres ee See | 14. 
Insoluble matter: 
TUE 2UUh J. lei Ae ee a eee es eee re hee vee os Ee 15 
_ LESS Elbo beet Se ae ee eee iy ores sek, So) aa 15 
TLDS Gis 1G 2, Sa NS a ee eee | Pag EP ie tees 16. 
“2 LU EDESEEL CE Pe a a ees eee =b- SULTS) & eee Rol eee | 18. 
LLL SS se 32M Sie Seen ee Be eee eee (5 saehie SVE | 18. 
UE Fo ee ee ee ee | Theoretical. |= 2. -222._/:: | 18. 
ES hl ia ie ie ey Wane ee | 19. 
TETRIS SS ae Fp ne 2 po ee ee 0. 2 ERR NE 8 fa bs) 19. 
_ J SADT ib st: Bi aN 2 eee ee Yo & bee ta ees 19. 
_. LS UTS Tr AS eed Ee ee eee eee 1 AL ER SS 19 
 Uheg i ee are eee a eee eee | 1 oy p| freee be. /19 
2 CD ETDE DE eS Deh tips eee oie I Si Alien age, es eg Lit ei 21, 22, 23 
Ether extractives: 
POUL. aol ee ee (By siya | eee ae te 23 
ST S's Rie Saree et eee Gay SRLS fos £8 | 23 
2 Diba 36h a ee eee eee eee Ch A med WERT SS Car tp 24. 
ec re tb ee ee eee Gls ate a eee 24. 
SEI CONGI 9 PY 9 ye Sti bei ree ies _e. HP heoretieals t{ 25.20) 24. 
oo Dd. sa bee ee ee eee ee eee 71.9 |. 26. 
sl Eee Re ee ee ees Sak 2 02) oh es hee eee 82.0 | 26. 
oC marily 2 eae EN es ee eee eee ee ee Oe | 0. 03 
_ 1 Although no limit is here defined, a statement of the percentage found by analysis must be incorporated 
in the foundation and supplemental affidavits (70). 
Naphthol yellow S is a light yellow or orange-yellow powder, 
which burns with yellow scintillations. The free acid érystallizes 
from hydrochloric acid solution in fine needles. The dye is readily 
soluble in water, producing a yellow solution, the color of which is 
