Nitrogen determination in compound fertilizer according to Devarda

KjelFlex K-360 with Devarda Splash Protector, Metrohm Titrino 877

Nitrogen is the most needed nutrient by crops, it is mainly absorbed by plants in the form of ammonium nitrogen and nitrate/nitrite nitrogen. The application of nitrogen fertilizer not only improves the yield but also the quality of the crop. From this aspect, the nitrogen content is a significant factor that affects the quality of the fertilizer. In this Application Note, the total nitrogen content and nitrate/nitrite nitrogen content in a fertilizer sample were determined by Devarda distillation. The nitrate/nitrite is reduced to ammonium with Devarda’s alloy, distilled by steam, absorbed by boric acid and titrated by sulfuric acid. To ensure the accuracy of the results, sodium nitrate was also tested as a reference for recovery. Due to formation of hydrogen gas during the reaction between alkali and Devarda’s alloy, the samples foam a lot with a strong reaction. With the introduction of steam, the gas stream into the condenser is very fast and sodium hydroxide aerosols can pass into the condenser which would falsify the results for nitrogen. Here, the specific Devarda Splash Protector was necessarily used to prevent that: it operates like a scrubber where all possible sodium hydroxide aerosols are scrubbed-off the gas stream.

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