Assay (HClO 4 titration) 99-100.5% pH(5% water) 7.5-9.0 Appearance of solution passes test Insoluble matter in water max 0.025% Acidity or alkalinity passes test Chloride(Cl) max 0.005% Oxalate(C 2 O 4 ) max 0.03% Sulphate(SO 4 ) max0.01% Tartarate passes test Heavy metals(as Pb) max 0.001% Arsenic(As) max 0.0001% Mercury (Hg) max 0.0001% Lead(Pb) max 0.001% Sodium(Na) max 0.3% Copper(Cu) max 0.002% Zinc(Zn) max 0.002% Reaction against H 2SO 4 passes test Readily carbonisable substancepasses test Water 4.0-7.0% Loss on drying (130 oC) 3.0-6.0