SCHEDULE 2 METHODS OF ANALYSIS

8b. DETERMINATION OF DIFFERENT FORMS OF NITROGEN IN THE SAME SAMPLE — IN THE ABSENCE OF CYANAMIDE NITROGEN

Total soluble nitrogen

3.5  Urea nitrogen, either:

3.5.1 By conversion using urease, into ammonia, which is determined by titration with a standard solution of hydrochloric acid.

Or:

3.5.2 By gravimetry using xanthydrol: although biuret will also be precipitated by xanthydrol, this should not give rise to a significant error in the determination since its level is generally low in absolute value in compound fertilisers.

Or:

3.5.3 By difference, according to the following table:

Case	Nitric nitrogen	Ammoniacal nitrogen	Difference
1	Absent	Present	(3.1.1) – (3.4)
2	Present	Present	(3.2) – (3.4)