FIELD: chemistry, water quality control, method for quantitative estimation of organic substance properties in aqueous solutions. ^ SUBSTANCE: indicator plate is immersed in aqueous solution and according to alteration of aqueous solution composition chemical activity of organic substances in this solution is determined. In clamed method tree vessels are used. Two vessels contain aqueous solution to be tested and the third vessel contains control aqueous solution free from organic contamination. In aqueous solutions containing in the second and third vessels indicator plates are immersed, then aqueous solutions in all vessels are heated up to 95-105°C, held at this temperature for 55-65 min, cooled to 15-25°C, filtered though membrane filter with pore size of 0.46 mum, then iron content is measured in all vessels and chemical activity of organic substances in aqueous solutions is calculated according to equation ka=DeltaFe/Fe1, wherein DeltaFe = Fe2- Fe1- Fe3; Fe1 is iron content in the aqueous solution of
