The Fertilisers (Sampling and Analysis) Regulations 1991

SPECIAL CASES

Samples not to be ground

6.—6.1 For those samples where the amount of phosphorous pentoxide solubile in 2percnt; citric acid and the fineness of grinding are to be determined, the sample should be well mixed (soft lumps may be disintergrated by lightly crushing) and divided into two parts, which are as identical as possible. The above mentioned determinations shall be carried out on the unground sample. All other determinations shall be carried out on the sample prepared in accordance with the directions in paragraph 5.1.

Products which may be difficult to grind mechanically, including products with abnormal moisture or products which become doughy through grinding

6.2 Some products such as superphosphate may become doughy if ground mechanically. In these case crush the sample in a mortar (4.2) so that all the material passes through a 1.0 mm sieve (4.3). Place the material so crushed in a clean container (4.4) and seal it until required for analysis.

Organic materials

6.3 Some organic materials may be of such a nature that the procedures given above cannot be used (for example fresh guano, leather, wool and animal residues). In these cases the analyst should use the best practicable means to obtain a representative sample.

Fertilisers comprising several different materials

6.4 These fertilisers include materials with marked differences in texture or mechanical properties (hardness, density, etc). They may be difficult to grind entirely (for example mixtures of organic and inorganic materials) or they may segregate during handling (for example “Kalimagnesia”). Special procedures are necessary in these cases:

6.4.1 for mixtures other than those in 6.4.2, follow the procedure in 5.1.1, repacing the 0.5 mm sieve by one with apertures of 0.18 mm. A grinding machine, capable of grinding the whole of the sample to the required fineness in one pass, is strongly recommended;

6.4.2 in the case of mixtures containing one or more very hard components, or mixtures containing organic materials, it may be difficult to grind and homogenise all the components. To avoid overgrinding some of the softer components proceed as follows:—

• grind the sample as in 5.1.1 or 5.1.2 to pass a 0.5 mm sieve. Re-seive the sample through a 0.18 mm sieve and reduce the residue to a convenient size by further grinding or other practicable means. Thoroughly remix the sample and place in a clean container (4.4).