The determination of nitrogen in agricultural materials by the nessler reagent. I.—preparation of the reagent

Abstract

Abstract 1. A modified Nessler reagent in which the ratio HgI 2 : KI : NaOH is 1 : 2.2 : 20 is described. It is clear and ready for immediate use and is less susceptible to interference by various cations. Distillation with phosphoric acid was satisfactory for preparing ammonia‐free water. The best range of ammonia‐nitrogen for this determination was from 0 to 100 μg. 2. The amount of the reagent used, the time and temperature of colour development, and the acidity of the test solution were critical factors in the accuracy of the determination. 3. Many cations interfered with the test to various extents. Among anions tested only arsenite, chromate, cyanide, dichromate and permanganate caused serious interference. Addition of sodium potassium tartrate, which did not alter the effects of anions, generally lessened cation interference. 4. With the modified reagent and under the conditions described quantities of ammonia‐nitrogen in the range 0–100 μg. may be determined with an accuracy of 2–3%.