Coal-fired power plants and waste incineration plants cause the emission of hazardous substances which attack the human body via exposure ways such as breathable air, food and drinking water. By reason of its remarkable chemical and physical characteristics this thesis pays attention to the contaminant mercury. Caused by its high vapour pressure there can be found considerable amounts of mercury in the clean gas side of incineration plants although they are equipped with filtration and off-gas treatment. Different methods of flue gas purification during the incineration, in the coarse separation and in the precision cleaning have to put a stop to the mercury emissions. It is planned to investigate for the conventional FGD - wet scrubbing (using a wet limestone scrubber for flue gas desulfurization) in pilot scale concerning the distribution of the mercury input from the raw gas on waste water, clean gas and gypsum by-product. Therefore, as an initial step the main part of this thesis is to find a reproducible dosing of elemental mercury for gas cleaning tests. Different options for dosing mercury are being compared experimentally.