Determination of nitrogen by microdiffusion in mason Jars. I. inorganic nitrogen in soil extracts

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Abstract
Simple microdiffusion methods are described for determination of NH4 +, NO3 ‐, and NO2 ‐ in soil extracts. These methods involve diffusion of NH3 in a 473‐mL (1‐pint) wide‐mouth Mason jar, the diffused NH3‐N being collected in 3 mL of boric acid‐indicator solution in a 60 mm (dia.) Petri dish suspended from the Mason jar lid, for quantitative determination by titrimetry (0.0025 M H2SO4). Magnesium oxide is used to liberate NH4 +; Devarda's alloy is used to reduce NO3‐ and NO2 ‐ to NH4 +; and sulfamic acid is used to eliminate NO2 ‐. Depending upon the volume of soil extract (10–50 mL), diffusion at room temperature (a20°C) was complete in 18–72 h with orbital shaking, and in 24–86 h without shaking. The methods gave quantitative recovery of NH4 +, NO3 ‐, and NO2 ‐added to soil extracts. A potential source of interference in the methods involving use of Devarda's alloy is the liberation of NH4 +‐N from alkali‐labile organic‐N compounds.