The Fertilisers (Sampling and Analysis) Regulations (Northern Ireland) 1991

Preparation of the solution for analysis

Fertilisers containing little or no organic matter

6.1—6.1.1 Weigh to the nearest 0.001 g, 2.5 g of the prepared sample and transfer to a 400 ml beaker. Add 50 ml water and 5 ml hydrochloric acid (3.3) and evaporate to dryness on a steam bath. Add to the residue 125 ml water and 50 ml ammonium oxalate solution (3.2) and boil for 30 minutes. If necessary, a small quantity of potassium-free antifoaming agent may be added. Cool the mixture, add a slight excess of ammonia solution (3.1) and allow to cool. Transfer to a 250 ml graduated flask, dilute to the mark with water, mix and filter through a dry paper.

Fertilisers containing organic matter

6.1.2 Weigh to the nearest 0.01 g, 10 g of the prepared sample into a suitable crucible and place in a cold muffle furnace. Gradually raise the temperature to about 475°C (not to exceed 500°C). Maintain at this temperature for at least 16 hours and then open the furnace and allow the crucible to cool. Grind the residue to eliminate any lumps, add 50 ml water and 10 ml hydrochloric acid (3.3) and evaporate to dryness on a steam bath. Add to the residue 125 ml water and 50 ml ammonium oxalate solution (3.2) and boil for 30 minutes. Cool the mixture, add a slight excess of ammonia solution (3.1) and allow to cool. Transfer to a 500 ml graduated flask, dilute to the mark with water, mix and filter through a dry paper.