# Fertilisers (Sampling and Analysis) Regulations (Northern Ireland) 1996, Paragraph 8: DETERMINATION


Aliquot portions to be taken
8.1 Take aliquot portions of the extracts which contain between 9 and 18 mg of magnesium ( = 15 to 30 mg of MgO).
Titration in the presence of Eriochrome black-T
8.2 Pipette an aliquot portion (8.1) of the solution to be analysed into a 400 ml beaker. Neutralise the excess acid with the 5 M sodium hydroxide solution (4.12) and check the pH. Dilute with water to approximately 100 ml. Add 5 ml of the buffer solution (4.9). The pH measured by meter must be 10.5 ± 0.1. Add 2 ml of the potassium cyanide solution (4.7) and three drops of the Eriochrome black-T indicator (4.6). Titrate with the EDTA solution (4.2). Stirring gently with the stirrer (5.1) (see 10.2, 10.3 and 10.4). Let ‘b' be the volume in millilitres of 0.05 molar EDTA solution used.
Titration in the presence of calcein or of calcon carbonic acid
8.3 Pipette an aliquot portion of the solution to be analysed equal to that taken for the above titration and place it in a 400 ml beaker. Neutralise the excess acid with the 5 M sodium hydroxide solution (4.13) using the pH meter. Dilute with water to about 100 ml. Add 10 ml of KOH/KCN solution (4.8) and three drops of the indicator (4.4 or 4.5). Stirring gently with the stirrer (5.1) titrate with the EDTA solution (4.2) (see 10.2, 10.3 and 10.4). Let ‘a' be the volume in millilitres of 0.05 M EDTA solution.

---
Source: https://www.legislation.gov.uk/nisr/1996/513/schedule/2/part/I/chapter/22./paragraph/8 (the official version)
Page: https://openlegislation.uk/fertilisers-sampling-and-analysis-regulations-northern-ireland-1996/schedule-2/part-I/chapter-22./paragraph-8
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.