BESTÄMNING AV NITROGEN I AVLOPPSVATTEN MODIFIERAD KJELDAHLMETOD / Determination of nitrogen in effluents. Modified Kjeldahl method
A modification of the Kjeldahl method has been tested in a collaborative study involving 16 laboratories. The method measures the sum of organic and inorganic nitrogen in industrial and municipal effluents. Nitrate and nitrite are reduced with Devarda’s alloy and the organic material is destroyed with sulphuric acid in the presence of copper. The ammonium formed is liberated with sodium hydroxide, distilled into boric acid and titrated with sulphuric acid. The extent to which the organic nitrogen is converted to ammonia depends on the types of bonds. The conversion of amino nitrogen is almost complete, but compounds with C-N-C bonds are only partially converted to ammonium. The results indicate that the method measures at least 80 °/o of the total of nitrogen in the effluent. The standard deviation between laboratories was 8 °/o for municipal effluents and 13 °/o for industrial effluents. “Complete abstract not presented.”