April, 1926 
CHEMISTRY AND ANALYSIS OF THE PERMITTED COAL-TAR FOOD DYES 
By JosepH A. AMBLER, Chemist, W. F. Cuarke, Assistant Chemist, O. L. EvEN- 
SON, Assistant Chemist, and H. Wass, Associate Chemist, Color Laboratory, 
Bureau of Chemistry 
CONTENTS 
Page | Page 
OLE TES Lie ee ee ee 1 | Methods of analysis of permitted coal-tar food 
Chemistry of permitted coal-tar food dyes____- 2 dyes—Continued. 
| ULPL MIS: noi eee eee 2 Tron, aluminium, calcium, and magnesium___ 19 
(TES inte) ee i eS eS ee eee 4 Eseries) 407-64 rit Se SE ee 20 
_ ULLFER Ts) ore el pee 2 ae 5 RRERer OXEFACELYOS © £512 ee sgt ee 23 
UDR ive tee ie ee eee 6 Bolpur in color. 22 eS ee 24 
mapesnol yellows. 2-2 2S 7 Golonneid = 223 Fase tre oye Se es eee 24 
SES TIS ete ee eee ae 8 Pure coal-tar Gy@-- = a ee 26 
_ LL UB ited RN Soe eee eee eee 9 | Matter insoluble in carbon tetrachloride____-- 27 
LLL EE ee eee aes 10 Water esiractives. 2. 2-—) 27 
OU SEP ds ee ee ae Stiae  WrClemtie Tih. so Oe ae, ae ye eee 27 
Light green S F yellowish___________________ 11 Lower sulphonated dyes__=_--.2._.-_-_ 2-2 28 
_ DEO SC ed ee ee 12 Boiling point of ¥-cumidine from ponceau3R_ 29 
Methods of analysis of permitted coal-tar food TIsomerie and similar dyes in amaranth________ 3 
[EL Be 2b ae ei ie ee eee 13 Sedinnviodicle fat. oe ee eee 30 
El Sus .'. 2, Dee ee ee eee 13 Todine organically combined ________________- 30 
ereparatione@tsawiple =) 2 ee 14-00) etal halppenss sls core tc. 2 te et od ee 31 
_ ULE LT te Le er Sear i4 Sodium carbonate in erythrosine____________ 31 
Total water-insoluble matter_________________ i4 Orange II and other subsidiary dyes in 
Nonvolatile water-insoluble matter__________ 15 | SEtipee © Ste ee 8S Se eee 33 
Seemmiehloninc=- 5 ee 15 | Martius yellow in naphthol yellow S__-_____- 33 
Sembiettpmigiiages) © Fes = 3 a PRG. FP Giaitroven Feri te se, ee 2 ee 33 
ILLS PLT ie ee ee oe 18 | _ Color by spectrophotometer--__-.------------ 34 
Tr S| Sa ee a ee ee eee Ss 19 *}e8iiLerachreieited (202 2 5... 93 253 Sa Ee es 35 
INTRODUCTION 
In 1912 Hesse (25)! described the work on aniline dyes used in 
foods which was done in the Bureau of Chemistry after the passage 
of the Federal food and drugs act in 1907, and compiled the litera- 
ture on the subject then available. At that time only 7 coal-tar 
dyes were permitted for certification; during the next 10 years 4 
| new dyes were added, so that on January 1, 1926, i1 coal-tar dyes were 
| recognized as harmless and considered permissible for use in foods 
(Food Inspection Decisions 164, 175, 180, 184). Since the certifi- 
cation plan, discussed in detail by Hesse (25), was devised it has been 
found necessary from time to time to change certain details of the 
rocedure and of the methods of analysis. Several of these changes 
ave been given in food inspection decisions (Nos. 117, 129, and 159) 
1Ttalic numbers in parenthesis refer to ‘‘ Literature cited,’’ page 35. 
73726°—26}——1 
