PERMITTED COAL-TAR FOOD DYES 3 
Care is necessary also in selecting the “R” acid. This acid should 
be free from the isomeric ‘‘G” acid ($-naphthol-6—8-disulphonic 
acid) and from the lower sulphonated Schaeffer’s acid (6-naphthol- 
6-sulphonic acid). The presence of either of these impurities in the 
intermediate makes it practically impossible to remove the resulting 
subsidiary dye from the finished product. 
Unless sufficient care is used in the coupling and other procedures 
a batch wili develop a very unpleasant odor, which persists when 
the dye is used in coloring food. This odor is probably the result of 
side reactions, which may occur during the diazotization and coup- 
ling of the y-cumidine, giving rise to phenolic substances or other 
degradation products. 
Ponceau 3R is a dark-red powder, which dissolves in water, form- 
ing a cherry-red solution. It is only slightly soluble in alcohol. 
The addition of hydrochloric acid to an aqueous solution does not 
change the color, but the addition of sodium hydroxide precipitates 
from it a yellow powder. Ponceau 3R dissolves in concentrated 
sulphuric acid to form a cherry-red solution, which remains un- 
changed in color upon dilution with water. 
In 1878 the following patents for the preparation of ponceau 3h 
were issued: German patent 3,229 (56); British patent 1,715 (66); 
French patent 124,811 (56). In1881 United States patent 251,163 
(56) was issued. 
The analytical data required in foundation and supplemental affi- 
davits (70), the methods of analysis, and the purity specifications 
are listed in Table 1. 
TABLE 1.—Specifications for ponceau 3R 
J 
pip aoe i =f ; 
tolerance Minimum ethod o 
Component (ratio to pure} tolerance analysis 
coal-tar dye) | 
: Per cent Per cent Page 
1S SFP Ue eS i ee 2G ewe ee 14. 
Insoluble matter: 
(TL eke So a ee eee ee ee ee PE op Eee ee ee eT 75; 
_ (DVS C= = 5 es oe ee eee A galg | |laeae een 15. 
EL BEL DE Gc = su ae eee ee een ert ole aE Be canoe ee 8 15, 16. 
STE SPELT ELEGY rh 0 oe Sa 2 a a = Mae as | See ee ive 
oe 4 ae ee ee Che) 5) be 18. 
| CPDL Gitte 22 bn Se 5 ee nernee Sk ane Theoretiealss} 2. --=- === 18. 
ie ee ee INGHe ae ae 19. 
| is Lee le ee ee ee ee Ce ees eee ae 19. 
0 SE SRST? Lele ie hg Se el a ee 5 ee (eee Be ee 19. 
0 LUTTE Ss sis le ete pee an ee i eos, eee, eee ee 19. 
0 oe eee een 222. ee ee ee eee a eee Pe re 19. 
5 LE |e SS SIGE er eee ane FTA. aes.) tae | 22, 23. 
Ether extractives: | 
(SIEM tee. ata lp a ee ee ee (4) {ex ee as 23. 
pra ee ek ee ie meee | | 23. 
(ih Ea se eee eee eee "ce eg =, aan | 24, 
diss =i ee eee Se Sh Bes ge es | 24. 
5 a ee ee Theoretical. |-__-__-_____ | 24, 
7) naa 5 eager aE a ante ee ieee ees 74.7 | 25. 
Se MF Ep 2 he ed eed aad a eg a ee es Se | ee ee 82 | 26. 
Sewersalphonated dyes._____.-===s =. ss 5.0 bet reese 
=a. .- .- . 29. 
Boiling point of crude ¥-cumidine, or of ¥y-cumidine by |_------------- 2 220 29, 30. 
reduction of dye. | 
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). ue 8 y y porate 
? Degrees centigrade. 
