The Fertilisers (Sampling and Analysis) Regulations 1996

15. EXTRACTION OF TOTAL CALCIUM, TOTAL MAGNESIUM, TOTAL SODIUM AND TOTAL SULFUR IN THE FORM OF SULFATES

1.    SCOPE

This method is for the extraction of total calcium, total magnesium, total sodium and total sulfur present in the form of sulfates.

2.    FIELD OF APPLICATION

This method applies to all fertilisers, for which a declaration of the total calcium, total magnesium, total sodium and total sulfur in the form of sulfates is required.

3.    PRINCIPLE

Dissolution by boiling in dilute hydrochloric acid.

4.    REAGENTS

Diluted hydrochloric acid; One volume of hydrochloric acid (p = 1.18g/ml) plus one volume of water.

5.    APPARATUS

Electric hot plate with adjustable temperature.

6.    PREPARATION OF THE SAMPLE

See method 1.

7.    PROCEDURE

Test sample.

Calcium, magnesium, sodium and sulfur in the form of sulfates are extracted from a test sample of 5 g weighed to within 1 mg. However, when the fertiliser contains more than 15% of sulfur (S) i.e. 37.5% SO3, and more than 18.8% of calcium (Ca) i.e. 26.3% CaO, the extraction of calcium and sulfur is carried out on a test sample of 1 g, weighed to within 1 mg. Place the test sample in a 600 ml beaker.

Preparation of the solution.

Add approximately 400 ml of water and, taking care when the sample contains a significant quantity of carbonates, 50 ml of dilute hydrochloric acid (4.1) a small amount at a time. Bring to the boil and maintain for 30 minutes. Allow to cool, stirring occasionally. Transfer quantitatively into a 500 ml graduated flask. Make up to volume with water, and mix. Pass through a dry filter into a dry container, discarding the initial portion. The extract must be completely clear. Stopper if the filtrate is not used immediately.