Sum of volatile matter at 135 °C (275 °F) and chlorides and sulfates (calculated as sodium salts), not more than 15 percent.
Water insoluble matter, not more than 0.4 percent.
Isatin-5-sulfonic acid, not more than 0.4 percent.
5-Sulfoanthranilic acid, not more than 0.2 percent.
Disodium salt of 2-(1,3-dihydro-3-oxo-7-sulfo-2H-indol-2-ylidene)-2,3-dihydro-3-oxo-1 H-indole-5-sulfonic acid, not more than 18 percent.
Sodium salt of 2-(1,3-dihydro-3-oxo-2H-indol-2-ylidene)-2,3-dihydro-3-oxo-1 H-indole-5-sulfonic acid, not more than 2 percent.
Lead (as Pb), not more than 10 parts per million.
Arsenic (as As), not more than 3 parts per million.
Mercury (as Hg), not more than 1 part per million.
Total color, not less than 85 percent.
21 C.F.R. §74.102