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


4.1 Formaldehyde, 25-35% solution, filter if necessary before use.
4.2 Potassium chloride.
4.3 Sodium hydroxide, 10 M solution. Care should be taken to ensure that the sodium hydroxide is free from potassium.
4.4 Indicator solution: dissolve 0.5 g phenolphthalein in 100 ml 90% enthanol.
4.5 EDTA solution: 4 g of the dihydrated disodium salt of ethylenediaminetetra-acetic acid (EDTA) per 100 ml. Store this reagent in a plastic container.
4.6 STPB solution: dissolve 32.5 g sodium tetraphenylborate in 480 ml of water, add 2 ml sodium hydroxide solution (4.3) 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 paper. Store this reagent in a plastic container.
4.7 Wash liquid: dilute 20 ml of the STPB solution (4.6) to 1 litre with water.
4.8 Bromine water: saturated bromine solution in water.

---
Source: https://www.legislation.gov.uk/nisr/1996/513/schedule/2/part/I/chapter/11./paragraph/4 (the official version)
Page: https://openlegislation.uk/fertilisers-sampling-and-analysis-regulations-northern-ireland-1996/schedule-2/part-I/chapter-11./paragraph-4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.