Artificial flue gas from coal combustion was oxidized with aq. solns. of KMnO4, NaOCl, NaClO3, H2O2 and Ca(OCl)(2) to convert Hg vapours into Hg salts under lab. conditions. NaOCl2 was the most active oxidant. Fly ashes from industrial stocker-fired and pulverized fuel boilers were sepd. into fractions and analyzed for Hg content. The Hg content decreased with incereasing grain size of the ash.