The Fertilisers (Sampling and Analysis) Regulations 1991

REAGENTS

Joulie’s alkaline solution of ammonium citrate:

4.—4.1 this solution contains 400 g of citric acid monohydrate and 153 g of NH₃ per litre. Its free ammonia content is approximately 55 g per litre. It can be prepared by one of the methods described below:

4.1.1 In a litre graduated flask, dissolve 400 g of citric acid monohydrate in approximately 600 ml ammonia solution (d = 0.925 g/ml), containing 200 g NH₃ per litre; this may be prepared by diluting 760 ml ammonia solution (d = 0.880 g/ml) from a freshly opened bottle with water to 1 litre. The citric acid is added successively in quantities of 50 to 80 g maintaining the temperature below 50°C. Make up the volume to 1 litre with ammonia.

4.1.2 In a 1 litre graduated flask, dissolve 400 g of diammonium citrate in 300 ml of water. Add 440 ml of ammonia solution (d = 0.925 g/ml) (see 4.1.1 above). Make up the volume to 1 litre with water.

Verification of the total ammonia content:

take a 10 ml sample of the citrate solution and place it in a 250 ml flask. Make up to the volume with distilled water. Determine the ammoniacal nitrogen content on 25 ml of this solution according to Method 2. In these conditions the reagent is considered to be correct when the volume of 0.5 N sulphuric acid consumed is between 17.7 and 18.0 ml (1 ml 0.5 N H₂SO₄-0.008516 g NH₃). If this is not so add 4.25 ml of ammonia (d = 0.925 g/ml) per 0.1 ml below the 18 ml indicated above.

4.2 8-Hydroxyquinoline (oxine), powdered.