Determination of nitrate in soil and water by an adaptation of an Orange I method

Abstract

A procedure is described for the determination of nitrate in air-dry and field-moist soil and in water, by an adaptation of Middleton's Orange I method. The molar absorptivity for nitrate-nitrogen in solution is greater than 2 × 10⁴ 1 cm^–1 mol^–1 by the proposed method, and without further modification to the method 0·04–40 mg kg^–1 of nitrate-nitrogen in soil can be determined. The procedure is simpler and quicker than Middleton's method and is free from interferences, provided that procedures carried out before colour development are carefully standardised. Comparative analyses by a distillation method are included.