Paragraph 7 PROCEDURE

Test sample

• Take a quantity of fertiliser weighing 1 or 2 g depending on the declared content of 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. The 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

Add about 400 ml of water.

• Stopper the flask well. Shake vigorously by hand to disperse the sample, then place the flask on the shaker and shake for 30 minutes.

• Make up to volume with water and mix thoroughly.

Filter immediately into a clean, dry flask. Stopper the flask. Carry out the determination immediately after filtering.

Note:

If the filtrate gradually becomes cloudy, make another extraction following 7.1 and 7.2 in a flask of volume Ve. Filter into a calibrated flask of volume W which has previously been dried and has received 5 ml of dilute hydrochloric acid (4.1). Stop the filtration at the exact moment when the calibration mark is reached. Mix thoroughly.

• Under these conditions the value of V in the expression of results is:

  $$\mathrm{V}=\mathrm{Ve}\times \mathrm{W}/\left(\mathrm{W}-5\right)$$

• The dilutions in the expression of results depend on this value of V.