Colorimetric determination of Ammonium Procedure: In alkaline medium ammonium ions react with chlorine to form chloroamine which in the presence of a catalyst forms a blue coloured indophenol with phenols. (Reaction basis according to DIN 38406-E5)
Colorimetric determination of Nitrite In acidic solution sulphanilic acid or sulphanilamide are diazotised with nitrite. The diazonium salt is then coupled with an aromatic amine, forming an intensely coloured azo dye. Organic colloids, chlorine, humic acids and coloured heavy metal ions interfere.