Commission Regulation (EC) No 152/2009Show full title

M. DETERMINATION OF CRUDE ASH U.K.

1. Purpose and Scope U.K.

This method makes it possible to determine the crude ash content of feed.

2. Principle U.K.

The sample is ashed at 550 ^oC; the residue is weighed.

3. Reagents U.K.

Ammonium nitrate, solution 20 % (w/v).

4. Apparatus U.K.

4.1. Hot-plate. U.K.

4.2. Electric muffle-furnace with thermostat. U.K.

4.3. Crucibles for ashing made of silica, porcelain or platinum either rectangular (approx. 60 × 40 × 25 mm) or circular (diameter: 60 to 75 mm, height: 20 to 40 mm). U.K.

5. Procedure U.K.

Weigh out to the nearest mg approximately 5 g of the sample (2,5 in the case of products which have a tendency to swell) and place in a crucible for ashing which has first been heated at 550 ^oC, cooled down and tared. Place the crucible on the hot-plate and heat gradually until the substance carbonises. Ash according to 5.1 or 5.2.

5.1. Put the crucible into the calibrated muffle furnace set at 550 ^oC. Keep at this temperature until white, light grey or reddish ash is obtained which appears to be free from carbonaceous particles. Place the crucible in a desiccator, leave to cool and weigh immediately. U.K.

5.2. Put the crucible into the calibrated muffle-furnace set at 550 ^oC. Ash for 3 hours. Place the crucible in a desiccator, leave to cool and weigh immediately. Ash again for 30 minutes to ensure that the weight of the ash remains constant (loss in weight between two successive weightings must be less than or equal to 1 mg). U.K.

6. Calculation of results U.K.

Calculate the weight of the residue by deducting the tare.

Express the result as a percentage of the sample.

7. Observations U.K.

7.1. The ash of substances which are difficult to ash must be subjected to an initial ashing of at least three hours, cooled and then a few drops of 20 % solution of ammonium nitrate or water added to it (carefully, to avoid dispersal of the ash or the formation of lumps). Continue calcining after drying in the oven. Repeat the operation as necessary until ashing is complete. U.K.

7.2. In the case of substances resistant to the treatment described under 7.1, proceed as follows: after ashing for three hours, place the ash in warm water and filter through a small, ash-free filter. Ash the filter and its contents in the original crucible. Place the filtrate in the cooled crucible, evaporate until dry, ash and weigh. U.K.

7.3. In the case of oils and fats, weigh accurately a sample of 25 g in a suitably sized crucible. Carbonise by setting light to the substance with a strip of ash-free filter paper. After combustion, moisten with as little water as possible. Dry and ash as described under 5. U.K.