PERMITTED COAL-TAR FOOD DYES 23 
DETERMINATION AS ToTAL ARSENIC 
For ponceau. 3R, amaranth, erythrosine, orange I, naphthol yellow S, 
tartrazine, yellow A B, yellow O B, guinea green B, light green S F 
yellowish, and indigotine.—Weigh 10 grams of the dye into a 600 ¢. ¢. 
Kjeldahl flask or tall 600 c. c. beaker provided with a cover. ‘Treat 
with 15 c. c. of the concentrated sulphuric acid and 25 c. c. of the 
strong nitric acid and digest slowly under a hood until the nitric acid 
has been decomposed or volatilized and the mixture turns very dark. 
Cautiously add a few cubic centimeters of the strong nitric acid to the 
hot mixture, which will again become light yellow or orange, and heat 
to charring. Repeat the nitric acid treatment and the heating until 
the solution no longer shows a tendency to darken and remains yellow 
or colorless when evaporated until sulphur trioxide fumes are evolved. 
Allow the mixture to cool, add 200 c. c. of water, and make slightly 
alkaline with the strong ammonium hydroxide. Determine the ar- 
senic in the solution and calculate as directed in the first para- 
graph of this section, beginning with ‘‘ Then add 20 c. c. of the sodium 
phosphate solution.’”” The comparatively large quantities of reagents 
necessary for the destruction of the organic matter will usually con- 
tain appreciable quantities of arsenic, for which correction must be 
made by determinations on blanks. 
ETHER EXTRACTIVES 
REAGENTS 
Washed ether—Wash ether successively with three portions of 
water. For 1 liter of ether use three 150 c. c. portions of water. 
Dilute sodium hydroxide solution.—1 c. c. of 0.1 N alkali to 100. ¢. 
of water. 
Dilute hydrochioric acid.—1 ¢.¢. of 0.1 N acid to 100 c. c. of water. 
DETERMINATION _ 
For ponceau 3R, amaranth, orange I, naphthol yellow S, tartrazine, 
guinea green B, light green S F yellowish, and indigotine.—To deter- 
mine the neutral extractives, proceed as follows: Place in a separatory 
funnel that volume of the master solution which contains 10 grams of 
the dye and add water, if necessary, to bring the volume to 150 c. e. 
Extract with two successive 100 ¢. c. portions of the washed ether, 
shaking for one minute during each extraction. Remove the ether 
by decantation into a clean funnel and rinse the first funnel with 5 ¢. ¢. 
of ether, decanting into the second funnel. Reserve the color solu- 
tion. Wash the combined extracts successively with 35, 20, and 10 
ce. c. of water. Drain the ether into a beaker, rinse the funnel with 
5 ¢. c. of ether, and drain into the same beaker. Place the beaker in 
a dust-free atmosphere, allow the ether to evaporate to a volume of 
50 c. c., and transfer to a weighed flat-bottom 100 c. c. dish, previously 
dried to constant weight over sulphuric acid in a desiccator. Rinse 
the beaker with 5 c. c. of ether and drain into the same dish. Let the 
remainder of the ether evaporate, and dry over sulphuric acid to con- 
stant weight. Calculate as percentage of neutral ether extractives.’ 
To determine the alkaline extractives, proceed as follows: Prepare 
the color solution as directed in the Esai paragraph, using 
graduated cylinders in place of the funnels, if the emulsions which 
2 Run two blanks on the washed ether and deduct the average result. 
