Paragraph 8 EXPRESSION OF RESULTS

See Method 25d (8).

The percentage of cobalt in the fertiliser is given by:

$$\mathrm{Co}\mathrm{\%}=\mathrm{[}\left(\mathrm{x}\mathrm{s}-\mathrm{x}\mathrm{b}\right)\times \mathrm{V}\times \mathrm{D]}/\left(\mathrm{M}\times 104\right)$$

If Method 25c is used:

$$\mathrm{Co}\mathrm{\%}=\mathrm{[}\left(\mathrm{x}\mathrm{s}-\mathrm{x}\mathrm{b}\right)\times \mathrm{V}\times \mathrm{2D]}/\left(\mathrm{M}\times 104\right)$$

where:

• Co is the quantity of cobalt expressed as a percentage of the fertiliser;

• x_s is the concentration in μg/ml of the Co in the test solution (6.2);

• x_b is the concentration in μg/ml of the Co in the blank solution (7.1);

• V is the volume in ml of extract obtained in accordance with Method 25a or 25b;

• D is the factor corresponding to the dilution carried out in 6.2;

• M is the mass in grams of the test sample taken in accordance with Method 25a or 25b.

Calculation of the dilution factor D: if (a₁), (a₂), (a₃), . . . , (a_i) and (a) are aliquot portions and (v₁), (v₂), (v₃), . . . , (v_i) and (100) are the volumes in ml corresponding to their respective dilutions, the dilution factor D is given by:

$$\mathrm{D}=(\mathrm{v}1/\mathrm{a}1)\times (\mathrm{v}2/\mathrm{a}2)\times (\mathrm{v}3/\mathrm{a}3)\text{x . . . x (v}\mathrm{i}/\mathrm{a}\mathrm{i})\times (100/\mathrm{a})\mathrm{.}$$