Assay(by acidimetry) min 97.0%Carbonates(as BaCO3) max 2.0%Substances insoluble indilute hydrochloric acid max 0.01%Chloride(Cl) max 0.002%Sulphide(S) max 0.001%Heavy metals(as Pb) max 0.002%Calcium(Ca) max 0.005%Iron(Fe) max 0.001%Strontium(Sr) max 1.0%Substances not precipitated bydilute sulphuric acid(as Sulphate) max 0.2%