The Fertilisers (Sampling and Analysis) Regulations 1991

REAGENTS

4.—4.1 Methanol.

4.2 Sulphuric acid solution, approximately 0.1 N.

4.3 Sodium hydroxide solution, approximately 0.1 N.

4.4 Alkaline solution of potassium sodium tartrate:

• In a 1 litre graduated flask dissolve 40 g of sodium hydroxide in 500 ml of water and leave to cool. Add 50 g of potassium sodium tartrate (KNaC₄H₄O₆.4H₂O). Make up to the mark and mix. Leave standing 24 hours before use.

Copper suplhate solution:

4.5 In a litre graduated flask dissolve 15 g of copper sulphate (CuSO₄.5H₂O) in 500 ml of water.

• Make up to the mark and mix.

Biuret standard solution:

4.6 In a 250 ml graduated flask, dissolve 0.250 g of pure biuret(1) in water. Make up to the mark and mix. 1 ml of this solution contains 0.001 g of biuret. This solution should be freshly prepared.

Methyl red indicator solution:

4.7 Dissolve 0.1 g methyl red in 50 ml 95% ethanol and make up to 100 ml with water. Filter if necessary.

(1)

Biuret can be prified beforehand by washing with ammoniacal solution (10%), then with acetone and drying in a vacuum.