Indicator

superior grade

top grade

qualified

Sulfuric acid(H₂SO₄)ω/ %   ≥

92.5 or 98.0

92.5 or 98.0

92.5 or 98.0

ash content ω/ %  ≤

0.02

0.03

0.10

ferrum (Fe)ω/ %  ≤

0.005

0.010

—

arsenic (As) ω/ %  ≤

0.0001

0.005

—

Mercury (Hg)ω/ % ≤

0.001

0.01

—

lead (Pb)ω/ % ≤

0.005

0.02

—

transparency / mm  ≥

80

50

—

chroma

Not deeper than the standard color