PERMITTED COAL-TAR FOOD DYES 5 
ERYTHROSINE 
Erythrosine (C,,.HsO,I,Na,), a xanthene dye, is the sodium salt of 
tetra-iodofluorescein, containing the equivalent of 1 molecule of water 
firmly bound in the molecule (22,73). It seems to be impossible to 
remove this molecule of water without destroying the coloring mat- 
ter itself. Erythrosine is prepared by iodinating fluorescein, a dye 
made by condensing phthalic anhydride with resorcinol, usually 
aided by zinc chloride or sulphuric acid (12, 58, 61, 62). The pro- 
cedure must be such that 4 atoms of iodine are introduced into the 
molecule. This step is the one which requires the most attention in 
the manufacture. The conditions under which this may be done 
successfully can be determined only by experimentation. 
KErythrosine is a brown powder, which dissolves in water to form 
a cherry-red solution that shows no fluorescence in ordinary light. 
When hydrochloric acid is added to its solution, a yellowish-brown 
recipitate of the free color acid is produced. The addition of sodium 
Be troxide produces a red precipitate soluble in excess of the reagent. 
The addition of concentrated sulphuric acid dissolves erythrosine, 
forming a brownish-yellow solution, which evolves iodine on heating 
and from which the brownish-yellow color acid is precipitated on 
diluting with water. The color acid is insoluble in water and is 
recipitated from solutions of the dye, even by very weak acids. 
or this reason erythrosine is not suitable for use in coloring food 
products and beverages which have acid reactions. 
In 1899 German patent 108,838 (67) for the preparation of ery- 
throsine was issued. 
The analytical data required in the foundation and supplemental 
affidavits (70), the methods by which the dye may be analyzed, and 
the purity specifications are listed in Table 3. 
TABLE 3.—Specifications for erythrosine 
pa joot F = 
olerance Minimum ethod of 
Component (ratio to pure| tolerance analysis 
coal-tar dye) 
Per cent Per cent Page 
TSM SiS a eR ea T5SQzc eo) yee os 2 tee 14. 
Insoluble matter: 
Olli LI phe ee ee pave NY, er eee 15. 
 CIDPT LST) See SY 2 ee or ey i Ree Pal Seas eee 15. 
IEE, Gli ie ra ea a ae sa ca atpeel e ee ae r 16. 
UIPPTIESTILIS TT AbO oe eee Lh ge Ste Te 1Ohs eat =. 22S? is 
DREN COUAS ae eee i oy a Qin, Pee ee. ei es 18. 
| SEETEE, TICE CCL G7 Lp a cee ee ‘Theoreticale |i =. 5--5_ 18. 
SueemayeTMCh Sweets ks ms a ee Pe None] =2- os —" =. <= 19. 
Pupmecinpiteeeeenpes o) fre or) yee t a For OF So eee oe 19. 
meaalesteriateeeeee gan Po Ts i SPOT S| i aire sae: 19. 
MMMRISAE ERTIES ee en et Si fe dso note ee Fe 2 19. 
Dee ne Le ee eee eee Rte 1 Bese | 19. 
TE EULER C75 en a aa 0 ee NOOT4Ash ee = 22, 23. 
Ether extractives: 
LUPT\EREL Lo. 2 sie gS PEE i ae ae ee (ee Rae | oe ce 24. 
7 wi lel ORs EY eet eee CEG Welle | 24. 
TOUTE 2 Eee ae ai ee ee Seen ners mle ape Wa | Re ee Oe 24. 
4) GIT 2 Se ee i ae ne ines eee ean 76.30 | 26. 
MERE CVC ta Penn Tk oo ae Py ee Foe AL eT CE ee io Re F 82.00 | 26. 
Se ees Soe a ee ee Si St ll RO eae | 30. 
Todine organically combined_-______________________________- ee ee 255.70 | 30. 
EES EES ee er era eee Came eee 2 56. 63 | 31. 
IRRITAG 2 Pr Sayeed | eee nes saligate 
| 
erent Sabie See aT Se ee et he th 
_, ! Although no limit is here defined, a statement of the percentage found by analysis must be incorporated 
in the foundation and supplemental affidavits (70). : 
? Ratio to pure coal-tar dye. 
a 
