Maximum level of impurities: Insoluble in dilute hydrochloric acid 0.015%, Cl 0.002%, Water soluble titratable base 0.002meq/g, Oxidizing substances (as NO3) 0.005%, S 0.001%, K 0.005%, Na 0.02%, Ca 0.05%, Heavy Metals (as Pb) 0.001%, Fe 0.002%, Sr 0.7%