Assay (complexometric): 99.0 - 101.0 %

Insoluble matter: ≤ 0.005 %

pH-value (5 %; water; 25 °C): 3.5 - 6.0

Sulfate (SO₄): ≤ 0.002 %

Heavy metals (as Pb): ≤ 0.0005 %

Ca (Calcium): ≤ 0.001 %

Cu (Copper): ≤ 0.0005 %

Fe (Iron): ≤ 0.0005 %

K (Potassium): ≤ 0.001 %

Mg (Magnesium): ≤ 0.005 %

Na (Sodium): ≤ 0.005 %

Pb (Lead): ≤ 0.0005 %

Zn (Zinc): ≤ 0.001 %

Substances not precipitated by ammonium sulfide (as SO₄): ≤ 0.2 %

Substances reducing potassium permanganate (as O): ≤ 0.0005 %

Corresponds to ACS