http://www.legislation.gov.uk/nisr/1991/540/schedule/2/crossheading/determination-of-different-forms-of-nitrogen-in-the-same-sample-in-the-presence-of-cyanamide-nitrogen/paragraph/4.22/madeThe Fertilisers (Sampling and Analysis) Regulations (Northern Ireland) 1991Local GovernmentGovernment Printer for Northern Ireland2016-09-06AGRICULTURESCHEDULE 2METHODS OF ANALYSIS8a.DETERMINATION OF DIFFERENT FORMS OF NITROGEN IN THE SAME SAMPLE — IN THE PRESENCE OF CYANAMIDE NITROGENREAGENTS4.22Sodium carbonate solution, 10 g per 100 ml.