# Fertilisers (Sampling and Analysis) Regulations (Northern Ireland) 1996, Paragraph 3: REAGENTS


3.1 Formaldehyde, 25-35% solution, filtered if necessary before use.
3.2 Potassium chloride.
3.3 Sodium hydroxide, 10 M solution. Care should be taken to ensure that the sodium hydroxide is free from potassium.
3.4 Indicator solution: dissolve 0.5 g phenolphthalein in 100 ml 90% ethanol.
3.5 EDTA solution: 4 g of the dihydrated disodium salt of ethylenediaminetetraacetic acid (EDTA) per 100 ml. Store this reagent in a plastic container.
3.6 STPB solution: dissolve 32.5 g sodium tetraphenylborate in 480 ml of water, add 2 ml of sodium hydroxide solution (3.3) and 20 ml of a magnesium chloride solution (100 g of MgCl2.6H2O per litre). Stir for fifteen minutes and filter through a fine, ashless filter. Store this reagent in a plastic container.
3.7 Liquid for washing: dilute 20 ml of the STPB solution (3.6) to 1 litre with water.
3.8 Hydrochloric acid (ρ = 1.18 g/ml).

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Source: https://www.legislation.gov.uk/nisr/1996/513/schedule/2/part/II/chapter/5./paragraph/3 (the official version)
Page: https://openlegislation.uk/fertilisers-sampling-and-analysis-regulations-northern-ireland-1996/schedule-2/part-II/chapter-5./paragraph-3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.