... crystalline powder Assay (C3H7NO2),%(on dry matter) 98.5~101.5 Transmittance, % ≥ 95.0 pH Value 5.5~7.0 Heavy Metals (as Pb), % ≤ 0 ... Chloride (as Cl), % ≤ 0.02 Sulfate (as SO4), % ≤ 0.02 Ammonium as (as NH4), % ≤ 0.02 Arsenic (as As), % ≤ 0.0001 ...