Quality standard: HG/T2523-93ItemIndexHigh-class ProductFirst-class ProductQualified ProductMain Content (Zn ) (Dry Basis)≥ 57.557.056.5Ignition Loss 25.0-28.025.0-30.025.0-32.0Content of Heavy Metal ( of pb)≤ 0.040.050.05Water Content≤ 2.53.55.0Content of Sulphate (SO4)≤ 0.600.80——