a a 
ORANGE If AND OTHER SUBSIDIARY DYES IN ORANGE I 
To that volume of the master solution which contains i gram of 
dye add water, if necessary, to bring the volume to 100 c. c. and then 
10 ¢. c. of strong hydrochloric acid. Extract this solution by shaking 
successively in three 500 c. c. separatory funnels, each containing 
100 c. c. of amyl alcohol and 5 ¢. ¢. of strong hydrochloric acid. 
Wash each of the three amy] alcohol extracts by means of six 100 ¢. e. 
portions of normal sodium carbonate solution (53 grams of anhydrous 
sodium carbonate to the liter), passed successively through the fun- 
nels in the order first used. (In washing the acidified amyl alcohol 
solutions, shake gently at first, keeping the funnel upright and un- 
stoppered until the evolution of carbon dioxide is slow enough to 
* permit more vigorous shaking.) In the same manner wash the ex- 
tracts in the second and third funnels with two more 100 ¢. c. por- 
tions of the sodium carbonate and wash the extract in the third 
funnel with two additional portions of the carbonate solution. 
Dilute the amyi alcohol solutions by adding 350 ¢. c. of gasoline 
(specific gravity 0.65) to each funnel. Remove the dye by extracting 
completely with the requisite number of 10 c¢. c. portions of water 
passed through the funnels, reversing the order previously used. 
_ Bring the volume to 150 c. c. by adding water, add about 10 grams 
of sodium acid tartrate, and titrate under carbon dioxide with stand- 
ard titanium trichloride solution (p. 24). Run a blank, using 10 
erams of sodium acid tartrate and 150 c. c. of water, with 1 mg. 
of orange I for an indicator. Calculate as percentage of orange II, 
1c. c. of 0.1 N titanium trichloride being equivalent to 0.008756 
gram of the dye. 
MARTIUS YELLOW IN NAPHTHOL YELLOW S 
Dissolve 5 grams of the dye in 150 c. c. of water, add 5c. ec. of 
strong hydrochloric acid, and shake vigorously in a separatory 
funnel for one minute with 50 c. c. of gasoline (specific gravity 0.65). 
Separate the solutions and extract the aqueous liquid again with 25 
to 30 c. c. of the solvent. Combine the portions of gasoline, decant 
into a clean separatory funnel, and wash with four 25 c. c. portions 
of 0.25 N hydrochloric acid. Shake with a few. portions of 5 per cent 
sodium hydroxide solution to extract the martius yellow. Neutralize 
the alkaline dye solution with tartaric acid, add 5 grams of sodium 
tartrate, and titrate against standard titanium trichloride as directed 
on page 26. One cubic centimeter of 0.1 N titanium trichloride is 
equivalent to 0.002134 gram of martius yellow. 
Very small quantities may also be estimated colorimetrically (in 
neutral or slightly alkaline solution) by comparison with a standard 
ene! yellow S solution, the tinctorial power of which is considered 
to be eight-tenths thet of martius yellow. It is calculated as percent- 
age of martius yellow. 
TOTAL NITROGEN 
For ponceau 8R, amaranth, orange I, naphthol yellow S, tartrazine, 
yellow A B, yellow O B, guinea green B, light green S F yellowish, 
and indigotine.—Use the method of Dumas (17). 
For guinea green B, light green 8 F yellowish, and indigotine.—Deter- 
mine on 2-gram portions by Gunning’s modification of the Kjeldahl 
process (44). Use a little copper sulphate to assist the oxidation. 
PERMITTED COAL-TAR FOOD DYES 33 
