Specifications:

Assay (Purity) 99.5% min   
Specific gravity 1.035 1.037 g/cm3at 25 °C 
Index of refraction 1.431 1.433 nD20 
Acidity ≤ 0.20 ml of 0.10 N NaOH 
Water/Moisture 0.2% max 
Residue on ignition 4.0 mg max 
Chloride 5 ppm max 
Heavy metals(as Pb) 5 ppm max 
sas SO42- 10 ppm max 
Oxidizing substances Not required 
Arsenic 5 ppm max