The Fertilisers (Sampling and Analysis) Regulations 1996

Preparation of the solution

7.1  Weigh to the nearest 0.001 g,1 g of the prepared sample into the Kjeldahl flask. Add 0.5 g of powdered iron (4.2) and 50 ml of the stannous chloride solution (4.11), stir and leave standing for half an hour. During the time it is left standing, stir again after 10 and 20 minutes. Then add 10 g of potassium sulfate (4.3) and 30 ml of sulfuric acid (4.1). Boil and continue for an hour after the appearance of white fumes. Leave to cool and dilute with 100-150 ml of water. Transfer the suspension quantitatively into a 250 ml graduated flask, cool and make up to volume with water, mix and filter through a dry paper into a dry container. Discard the first portion of the filtrate.