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


4.1 Hydrochloric acid solution, 50% (V/V): dilute an appropriate volume of hydrochloric acid (ρ = 1.18 g/ml) with an equal volume of water.
4.2 Sulfuric acid, 0.05 M solution.
4.3 Sodium or potassium hydroxide, 0.1 M solution, carbonate free.
4.4 Sulfuric acid solution, approximately 30% H2SO4 (W/V), ammonia free.
4.5 Powdered iron reduced in hydrogen. (The prescribed quantity of iron must be able to reduce at least 0.05 g nitrate nitrogen.)
4.6 Sodium hydroxide solution, 30 g per 100 ml, ammonia free.
4.7 Indicator solutions:
Mixed indicator:
4.7.1 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 solution A and 2 volumes of solution B.
This indicator is violet in acid solution, grey in neutral solution and green in alkaline solution; use 0.5 ml (10 drops).
Methyl red indicator solution:
4.7.2 Dissolve 0.1 g methyl red in 50 ml 95% ethanol, make up to 100 ml with water and filter if necessary.
This indicator may be used (4-5 drops) instead of the preceding one.
4.8 Anti-bump granules of pumice stone, washed in hydrochloric acid and ignited.
4.9 Sodium nitrate.

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Source: https://www.legislation.gov.uk/nisr/1996/513/schedule/2/part/I/chapter/3a./paragraph/4 (the official version)
Page: https://openlegislation.uk/fertilisers-sampling-and-analysis-regulations-northern-ireland-1996/schedule-2/part-I/chapter-3a./paragraph-4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.