24 BULLETIN 1390, U. S. DEPARTMENT OF AGRICULTURE 
are usually formed may thus be more easily destroyed. To the 
reserved color solution add 2 c. c. of a 10 per cent sodium hydroxide 
solution and extract and rinse with ether. Reserve the color solution. 
Wash the combined ether extractives and rinsings successively with 
35 and 10 c. c. of the dilute sodium hydroxide solution. Evaporate 
the ether, dry, and weigh. Calculate as percentage of alkaline ether 
extractives.® 
To determine the acid extractives, proceed as follows: To the color 
solution reserved from the alkaline extraction add twice the volume 
of hydrochloric acid (1+3) necessary to neu- 
tralize. Repeat the procedure as directed for 
the neutral extractives, but do not reserve 
the color solution. Wash the ether extractive 
with the dilute hydrochloric acid. Calculate 
as peteen tare of acid ether extractives.° 
‘or erythrosine.—Determine as directed in 
the first paragraphs of this section, omitting 
the acid extraction. 
SULPHUR IN COLOR 
For ponceau 3R, amaranth, orange I, naphthol 
yellow S, tartrazine, guinea green B, light green 
S F yellowish, and indigotine.— Determine the 
sulphur content by the Carius method (/7). 
Deduct the sulphur equivalent to the sodium 
sulphate as determined on p. 17. Calculate 
as percentage of sulphur in color. 
For ponceau 8R, amaranth, orange I, naphthol 
yellow S, tartrazine, guinea green B, light green 
S F yelloursh, and indigotine.—Place about 0.2 
gram of the sample in a Parr calorimetric 
bomb and mix thoroughly with approxi- 
mately 10 grams of sodium peroxide. Add 
a few milligrams of sulphur-free sugar, if 
necessary, to aid in igniting the mass. Close 
the bomb and ignite. When cold open the 
bomb, place it in a 400 c. c. beaker, and cover 
the beaker with a watch glass. Add water 
through the lip of ie beaker until the poe 
.. Is covered. When the mass is completely 
aie fenuaetl esis Gee dissolved, remove the bomb from the baaker 
sab ice a and wash it carefully with water, uniting the 
washings with the solution. Cautiously acidify the solution with 
dilute hydrochloric acid and filter, if necessary. Determine the 
sulphuric acid as directed on page 17. Deduct the sulphur equivalent 
to the sodium sulphate (p. 17). 
COLOR ACID 
REAGENTS 
Standard titanium trichloride solution.—Add 150 c¢. c. of strong 
hydrochloric acid to 200 c. c. of commercial 15 per cent titanium 
trichloride solution and dilute to 2 liters. Titrate the required 
3 Run two blanks on the washed ether and deduct the average result. 
