An Improved Rapid Chromic Acid Method for Determining Total Nitrogen in Surface Soils

The proposed procedure consists of digesting soil with chromic and sulphuric acid mixture at 300 ± 10°C for 15 min followed by distillation of nitrogen. The method is about 4 to 5 hr more rapid and gave 6% higher values of nitrogen than the conventional Kjeldahl method when tested on 74 samples. A pre-treatment of soil with dilute H₂SO₄, Zn and reduced Fe included nitrate-nitrogen quantitatively. The method could be considered highly precise as the coefficient of variation was less than 3.5%.