Na2S2O3.5H2O M.W. 248.17 5 kgAssay 99.5-100.5%Insoluble matter max 0.003%Reaction pH 5.5-7.5Chloride(Cl) max 0.02%Nitrogen compounds(N) max 0.005%Sulphate and sulphite(SO4) max 0.1%Sulphide(S) max 0.0002%Calcium(Ca) max 0.002%Copper(Cu) max 0.0005%Iron(Fe) max 0.0005%Lead(Pb) max 0.0005%Magnesium(Mg) max 0.001%Potassium(K) max 0.001%