# Fertilisers (Sampling and Analysis) Regulations (Northern Ireland) 1996, Paragraph 4.1: Neutral ammonium citrate solution (pH = 7.0)


This solution must contain 185 g of citric acid monohydrate per litre and must have a specific gravity of 1.09 at 20°C and a pH of 7.0. The reagent is prepared as follows:
Dissolve 370 g citric acid monohydrate in about 1.5 litres of water and make an approximately neutral solution by adding 345 ml of ammonia solution (28-29% of NH3). If the NH3 concentration is lower than 28% add a correspondingly larger quantity of ammonia solution and dilute the citric acid in correspondingly smaller quantities of water.
Cool and make exactly neutral by adding the ammonia solution (28-29% of NH3) drop by drop, stirring continuously (with a mechanical stirrer) until a pH of exactly 7.0 at 20°C is obtained, keeping the electrodes of the pH meter (5.1) immersed in the solution.
At this point make up the volume to 2 litres and test the pH again. Keep the reagent in a closed container and check the pH at regular intervals.

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Source: https://www.legislation.gov.uk/nisr/1996/513/schedule/2/paragraph/4.1 (the official version)
Page: https://openlegislation.uk/fertilisers-sampling-and-analysis-regulations-northern-ireland-1996/schedule-2/paragraph-4.1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.