standard GB/T6009-2003.
Na2SO4                                 ≥99.0%
Water insoluble matter             ≤0.05%
Ca&Mg(as Mg)                        ≤0.15%
Cl                                           ≤0.35%
Fe                                           ≤0.002%
Water                                      ≤0.20%
Whiteness(R457)                      ≥85%