BS EN 15935:2021 pdf free download – Soil, waste, treated biowaste and sludge一 Determination of loss on ignition.
5 Interferences and sources of errors
LOt is an empirical parameter, thus in principle there is no interference connected to the determination. However, for some purposes the determination of LOt is used for the assessment of the content of organic matter in the sample. It should be noted that elemental carbon in the sample will be included in the loss on ignition value. Furthermore, any volatilisation or chemical reactions of inorganic compounds will also be included in the loss on ignition value.
Chemically bound water could be released during heating, thereby contributing to the loss on ignition.
Samples containing iron or other metals in low bonding state or in metallic state can be oxidized during heating, thereby contributing to the loss on ignition with a negative amount.
Sulphides present in the sample could be oxidized to sulphate during heating, thereby contributing to the loss on ignition with a negative amount.
Explosive ignition is likely to result in loss of residue from the crucible, thereby contributing to the loss on ignition with a positive amount. If such loss of residue is observed during the removal of the crucible from the furnace, the test shall be discharged and repeated taken the necessary precautions, e.g. using a smaller test portion.
Calcium hydroxide or calcium oxide present in large amounts (e.g. sludge conditioned with lime) can combine with sulphuric oxides liberated during ignition or with carbon dioxide formed during ignition resulting in a too low content of the loss on ignition. Such reactions can be avoided using the stepwise heating procedure stated in 7.4 combined with a sufficient ventilation rate in the furnace and a height of the sample layer in the crucible not exceeding 5 mm.
a) Solid waste samples to be comminute and reduced to a granular powder, preferably a particle size less than 200 aim. If no volatile substances are present in the sample, sample may be air-dried prior to comminuting. The drying temperature of the air-drying shall not exceed 40 °C.
b) Moist or pasty-like waste samples may be mixed with aluminium oxide until a granular material is obtained and then comminuted, preferably to a particle size less than 200 jim. In this case the ratio of aluminium to sample shall he considered in the calculation of the loss on ignition.
c) Liquid samples shall be homogenized immediately prior to the weighing of the test portion.
Foreign bodies or non comminutable material (as metallic parts such as nuts, blots, scrap) should be separated from the sample and the weight and nature of the material recorded.
7.3 Determination
The determination of loss on ignition can be performed using
— an undned sample (see 7.4);
— an air-dried sample;
— a sample after determination of dry matter at (105 ± 5) °C, in successive operations using the same crucible.
The dry matter is determined according to EN 15934.
NOTE This procedure can be combined with the determined according to EN 15934 by using a crucible (6.1) dried at (105 ± 5) °C.
Place a crucible (6.1) in the furnace (6.2) and heat to (550 ± 25) °C and hold for at least 20 mm. Transfer the crucible from the furnace after initial cooling on a metal plate (6.3) to a desiccator (6.4) and finish cooling to ambient temperature. Weigh the empty crucible using a precision scale (6.5) to the nearest 1mg.
Weigh into the crucible a test portion of 0,5 g to 5 g of the test sample to the nearest I mg, and place the crucible into the furnace. Larger masses may be taken if complete combustion can be ensured.
Raise the furnace temperature to (550 ± 25) °C and hold this temperature for at least 2 h.
Place the hot crucible containing the residue on ignition on a metal plate (6.3) for a few minutes. While still warm, transfer the crucible to a desiccator (6.4) and leave to cool to ambient temperature. As soon as ambient temperature is reached, weigh the crucible containing the ignition residue to the nearest 1 mg.