# Fertilisers (Sampling and Analysis) Regulations (Northern Ireland) 1996, Paragraph 4: REAGENTS


4.1 Nitric acid (HNO3 ρ = 1.40 g/ml).
4.2 Urea [(NH2)2 C O].
Ammonium biflouride (NH4HF2) solution (10% w/v)
4.3 Keep the solution in a plastic container.
Ammonium hydroxide solution (1 + 1)
4.4 Mix 1 volume of ammonia (NH4OH, ρ = 0.9 g/ml) with 1 volume of water.
Sodium thiosulfate standard solution
4.5 Dissolve 7.812 g of sodium thiosulfate pentahydrate (Na2S2O3.5H2O) with water in a litre volumetric flask. This solution must be prepared so that 1 ml = 2 mg Cu. For stabilization, add several drops of chloroform. The solution must be kept in a glass container and protected from direct light.
4.6 Potassium iodide (KI).
Potassium thiocyanate (KSCN) solution (25% w/v)
4.7 Keep this solution in a plastic flask.
Starch solution (about 0.5%)
4.8 Place 2.5 g of starch in a 600 ml beaker. Add about 500 ml of water. Boil while stirring. Cool to ambient temperature. The solution has a short preservation period. Its preservation can be extended by adding about 10 mg of mercury iodide.

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Source: https://www.legislation.gov.uk/nisr/1996/513/schedule/2/part/I/chapter/26g./paragraph/4 (the official version)
Page: https://openlegislation.uk/fertilisers-sampling-and-analysis-regulations-northern-ireland-1996/schedule-2/part-I/chapter-26g./paragraph-4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.