Determination of nitrogenous gases evolved from soils in closed systems
Abstract
A simple method is described for determining nitrogen oxide and nitrogen dioxide, evolved from soils, in closed systems. These gases are absorbed by an acidic solution of potassium permanganate, and the resulting nitrate is determined by a steam distillation method. Excess of permanganate is reduced with iron(II) sulphate and neutralised with sodium hydroxide solution. Ammonium in solution is removed by distillation with magnesium oxide, and nitrate is determined by distillation after reduction to ammonium by Devarda's alloy.
Nitrogen and dinitrogen oxide evolved from soils are measured using gas chromatography on a single 0.61-m column of molecular sieve 5A, temperature programmed to 250 °C at 39 °C min–1, after an initial period of 1 min at 35 °C. A complete analysis requires 19.5 min, and 2 µg of nitrogen can be determined quantitatively for each gas.