PERMITTED COAL-TAR FOOD DYES 35 
DETERMINATION 
Fill a 1 cm. cell with the dye solution prepared as directed and 
place it in front of one orifice of the spectrophotometer. Fill another 
cell of the same size with the solvent used and place it before the 
other orifice. The second cell corrects for any error which may be 
caused by the absorption of light by the solvent. Rotate the photo- 
meter contro! until the two fields appear matched and record the ex- 
tinction coefficient. The most accurate results can usually be ob- 
tained by rotating the photometer control rapidly back and forth, 
making first one field and then the other the darker, and stopping in 
the middle of the swing. With a little experience the extinction co- 
efficients can be determined to within 2 per cent. Record the ex- 
tinction coefficients for the point of maximum absorption and at 
least one point on each side of the maximum. For yellow A B and 
yellow O B determine the extinction coefficients at 440 yy and 450 py. 
The color content is found by dividing the observed extinction co- 
efficients by the extinction coefficients found for a 0.002 per cent 
solution at the same wave length and dissolved in the same buffer 
solution. 
LITERATURE CITED 
(1) AcTIENGESELLSCHAFT FUR ANILINFABRIKATION. 
Verfahren zur darstellung von Farbstoffen durch Condensation von 
Methylbenzylanilinsulfosiure oder Aethylbenzylanilinsulfosiure mit 
aromatischen und Oxydation der so erhaltenen Leukosulfosdiuren, Ger- 
man Patent 50,782 (1889); Dyes—rosaniline series, British Patent 
7,550 (1889); Pour un procédé de préparation de matiéres colorantes 
vertes et violettes, French Patent 198,415 (1889). 
(2) ANONYMOUS. 
New colouring matters. Fastred NS. In J. Soc. Dyers Colourists (1894), 
vol. 10, p. 150. 
(3) ANscHttz, R. 
Ueber die Constitution des Tartrazins. In Ann. (1897), vol. 294, p. 219; 
(1899), vol. 306, p. 1. 
(4) BADISCHE ANILIN UND SODAFABRIK. 
Verfahren zur Darstellung rother und brauner Naphtalinfarbstoffe, Ger- 
man Patent 5,411 (1878); Production of colouring matters for dyeing 
and printing, British Patent 786 (1878); Pour la production de matiéres 
colorantes pour la teinture et impression, French Patent 123,148 (1878); 
Improvement in dyestuffs produced from naphthylamine, U. S. Patent 
6) 204,799 (1878). 
5 
Verfahren zur Darstellung der Nitrosulfosiuren des Alphanaphtols und 
insbesondere zur Darstellung der Binitronaphtolsulfosiure, German 
Patent 10,785 (1879); Preparing colouring matters for dyeing and print- 
ing, British Patent 5,305 (1879); Pour la production de matiéres colo- 
rantes nouvelles dérivées de la naphtaline, French Patent 134,632 
(1880); Coloring-matter obtained from alpha-naphthol, U. S. Patent 
225,108 (1880). 
Verfahren zur Darstellung von gelben bis orangerothen Farbstoffen durch 
Condensation von Hydrazinen mit Dioxyweinsiure, German Patent 
34,294 (1885); Verfahren zur Darstellung von Tartrazinfarbstoffen, Ger- 
man Patent Application B-20,084 (1897); Improvements in the manu- 
facture of yellow and orange colouring matters suitable for dyeing and 
printing from dioxytartaric (carboxytartronic) acid, British Patent 9,858 
(1885); Improvements in the manufacture of colouring-matters and of 
new intermediate products, British Patent 765 (1897); Pour la prépara- 
tion de matiéres colorantes des hydrazines avec l’acide dioxytartrique, 
French Patent 169,964 (1885); Coloring-matter from phenylhydrazine, 
U.S. Patent 324,630 (1885). 
