FIELD: analytical chemistry; more particularly methods of identification of nitrate-ions. SUBSTANCE: composition is used for controlling water purification processes, identifying the content of nitrate-ions in foodstuffs, biological objects and soil extracts. Composition makes it possible to reduce labor intensity owing to elimination of filtration operation, to increase accuracy and expressness of identification of nitrate-ions. The composition, as diazonitration catalyst, comprises ammonium bromide, and as agents for creating optimum acidity succinate mixture of tartaric acid and ammonium, and azocomponent is chromotropic acid disodium salt, ratios of components being as follows, wt %: zinc dust, 2.0-6.0; ammonium bromide, 5.0-20; tartaric acid, 38-45; ammonium succinate, 38-56; sulfanyl acid, 0.5-1.5; chromotropic acid disodium acid, 1.0-2.5. Composition makes it possible to operate within wide acidity range of pH of 3.8 of the test solution, and is stable in time (1.5 years). In using composition identification time is reduced to 10 minutes. Composition comprises no carcinogenic components. EFFECT: improved properties of the composition. 3 ex
