Acidimetric Determination of NH4+-Nitrogen in Compound Fertilizers After Separation by Cold-Air Distillation

Ammonium nitrogen in compound fertilizers in the presence of nitrogen in various species was determined by acidimentry with 0.05 mol·L-1 HCl standard solution after separation by cold distillation. Appropriate amount of the sample was reacted with 60 mL of 550 g·L-1 K2CO3 solution in a distillation flask, to form gaseous NH3 which was carried over by cold air with flow-rate of 3 L·min-1 and absorbed in 3 portions of 50 mL of boric acid solution previously added into 3 separate absorption flasks conrected in series, during the course of 8 h. The solutions in the 3 flasks were titrated with HCl standard solution to a dark red color of the indicator. The cold distillation was carried on again for another one hour. The distillates were titrated again and if the consumption of HCl standard solution was less than 0.03 mL, the determination was concluded and content of NH4+-nitrogen was calculated on the base of the total volume of standard HCl solution consumed in the titration. From the results of 5 determinations each in analysis of 3 samples by the present method, values of recovery were found in the range of 99.7% to 100.1% with RSD′s (n=5) ranged from 0.12% to 0.55%.