Paragraph 7 PROCEDURE
Test sample
Take a quantity of fertiliser weighing 1 or 2 g depending on the declared content of element in the product. The following table shall be used to obtain a final solution which, after appropriate dilution, will be within the measuring range for each method. Samples should be weighed to within 1 mg.
| Declared content of trace element in the fertiliser (%) | > 10-< 25 | ≥ 25 |
| Mass of test sample (g) | 2 | 1 |
| Mass of element in the sample (mg) | > 200-< 500 | ≥ 250 |
| Volume of extract V (ml) | 500 | 500 |
| Concentration of element in extract (mg/l) | > 400-<1000 | ≥ 500 |
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Place the sample in a 250 ml beaker.
Preparation of the solution
If necessary moisten the sample with a little water, add 10 ml of dilute hydrochloric acid (4.1) per gram of fertiliser carefully, in small amounts, then add about 50 ml of water. Cover the beaker with a watchglass and mix. Bring to the boil on the hotplate and boil for 30 minutes. Allow to cool, stirring occasionally. Transfer quantitatively to a 500 ml volumetric flask. Make up to volume with water and mix thoroughly. Filter through a dry filter into a dry container. Discard the first portion. The extract must be perfectly clear.
It is recommended that the determinations be carried out without delay on aliquot portions of the clear filtrate, if not the containers should be stoppered.
Note:
Extracts in which the boron content has to be determined.
Adjust the pH to between 4 and 6 with concentrated ammonia solution (4.2).