Inorganic substances contained in the water

Dissolved, bivalent iron Fixing directly at the time of sampling with 

2 -bipyridyl forming a red-coloured complex which can be analyzed photometrically in the laboratory. 

Silicic acid (Si02) Decomplexing or depolymerization directly after sampling by adding the water sample to a digestion mix of perchloric and 

Nitrogen compounds, such as ammonium, nitrite and nitrate, or samples to 

Heavy metals For use in analysis according to the flame atom absorption method, the sample should be acidified using hydrochloric acid of reagent purity immediately after being drawn, and the samples should be taken in glass bottles and transported under refrigerated conditions. The quantity of hydrochloric acid should be noted for a blank experiment. 

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Most detergents (surfactants) are soluble in ethanol. The content of ethanol-soluble substances in the evaporation residue of a water sample therefore provides an indication of the scale on which these substances are present. It should be noted that other ethanol-soluble substances have a disturbing effect and that inorganic substances contained in the water may also pass into the ethanol extract. It is therefore advisable to re-extract the first extract with ethanol. 

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