... ,Annuual production:20,000mt Quality standard : GB1893-1998Item Company standardAssay ( as Na2S2O5 ) % ≥96.5Fe % ≤0.003ClarityclearHeavy metal (Pb)% ≤0 ... .0005As % ≤0.0001Usage1, As the material of medicine2, As curing agent of rubber3, As dechlorinating agent and scouring agent of ... of leather Moreover5, As the material of fine chemicals, or used as developer6, In food industry, as bleaching agent, ...