purity              ≥98%
cl                   ≤0.050%
NH4                ≤0.020%
SO4                ≤0.030%
iron                ≤30ppm
Pb                   ≤10ppm
As                   ≤1ppm
Other Amion Acids            negative
loss on drying                 ≤0.5%
ignition residue(H2SO4)            ≤0.10%
PH                        6.5～7.0