Paragraph 7 PROCEDURE
Test sample
Take a quantity of fertiliser weighing between 2 and 10 g depending on the declared content of the 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 (%) | < 0.01 | 0.01-< 5 | ≥ 5-10 |
|---|---|---|---|
| Mass of test sample (g) | 10 | 5 | 2 |
| Mass of element in the sample (mg) | 1 | 0.5-250 | 100-200 |
| Volume of extract V (ml) | 250 | 500 | 500 |
| Concentration of element in extract (mg/l) | 4 | 1-500 | 200-400 |
Place the sample in a 250 ml beaker.
Preparation of the solution
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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 watch glass and mix. Bring to the boil on the hot plate and boil for 30 minutes. Allow to cool, stirring occasionally. Transfer quantitatively to a 250 or 500 ml volumetric flask (see Table). 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.
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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 (4.2).