Water soluble matter, not more than 2.5%.
Chromium in 2% NaOH extract, not more than 0.1% as Cr2O3 (based on sample weight).
Boron (as B2O3), not more than 8 percent.
Total volatile matter at 1000 °C, not more than 20%.
Cr2O3 not less than 75%.
Lead (as Pb), not more than 20 parts per million.
Arsenic (as As), not more than 3 parts per million.
Mercury (as Hg), not more than 1 part per million.
21 C.F.R. §73.1326