Fineness, 100 percent shall pass through a 100-mesh sieve.
Loss on ignition at 600-650 °C, not more than 2 percent.
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. §73.1496