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


4.1 Sulfuric acid solution 50% (V/V): dilute an appropriate volume of sulfuric acid (ρ = 1.84 g/ml) with an equal volume of water.
4.2 Potassium sulfate.
4.3 Copper oxide (CuO), 0.3-0.4 g for each determination or an equivalent quantity of copper sulfate pentahydrate (0.95 to 1.25 g) for each determination.
4.4 Sodium hydroxide solution 30 g per 100 ml, ammonia free.
4.5 Sulfuric acid, 0.05 M solution. } for variant (a) (see page 21)
4.6 Sodium or potassium hydroxide, 0.1 M solution, carbonate free. } for variant (a) (see page 21)
4.7 Sulfuric acid, 0.1 M solution. } for variant (b) (see page 21)
4.8 Sodium or potassium hydroxide, 0.2 M solution, carbonate free. } for variant (b) (see page 21)
4.9 Sulfuric acid, 0.25 M solution. } for variant (c) (see page 21)
4.10 Sodium or potassium hydroxide, 0.5 M solution, carbonate free. } for variant (c) (see page 21)
4.11 Indicator solutions:
4.11.1 Mixed indicator:
Solution A: dissolve 1 g methyl red in 37 ml 0.1 M sodium hydroxide solution and make up to 1 litre with water.
Solution B: dissolve 1 g methylene blue in water and make up to 1 litre. Mix 1 volume of A with 2 volumes of B.
This indicator is violet in acid solution, grey in neutral solution and green in alkaline solution. Use 0.5 ml (10 drops).
4.11.2. Methyl red indicator solution:
Dissolve 0.1 g methyl red in 50 ml 95% ethanol, make up to 100 ml with water and filter if necessary. This indicator (4 to 5 drops) may be used instead of the preceding one.
4.12 Anti-bump granules of pumice stone, washed in hydrochloric acid and ignited.
4.13 Potassium thiocyanate.

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