BS ISO 1762:2015 pdf download – Paper, board and pulps — Determination of residue (ash) on ignition at 525 °C.
5 Apparatus 5.1 Heat-resistant crucibles, made of platinum, porcelain, or silica, with a capacity of 50 ml to 100 ml. 5.2? Muffle?furnace, capable of maintaining a temperature of 525 °C ± 25 °C. It is recommended to place the furnace in a hood or to provide means for evacuating smoke and fumes. 5.3 Analytical balance, accurate to 0,1 mg. 5.4 Desiccator. 6 Sampling and preparation of test specimen If the analysis is being done to evaluate a lot, obtain a representative sample of paper, board, or pulp as described in ISO 186 or ISO 7213, as relevant. Sufficient sample must be collected to allow for at least duplicate determinations and for determination of moisture content. Take a test specimen consisting of small pieces, not larger than 1 cm 2 , taken from various parts of the sample in such a manner as to be thoroughly representative of it. The total mass shall be at least 1 g moisture free and shall yield a weight of ash not less than 10 mg and preferably over 20 mg (See the Note in Clause 7). In a similar manner, obtain a moisture specimen from the sample. 7 Procedure Carry out the procedure in duplicate. Air-dry the test and moisture specimens in the laboratory atmosphere until they reach equilibrium moisture. Determine the moisture content on the moisture specimen as described in ISO 287 or ISO 638, as relevant. Weigh this specimen at the same time as the specimen used for ash determination. Heat the empty crucible (5.1) for 30 min to 60 min in the muffle furnace (5.2) at 525 °C ± 25 °C. Cool it to room temperature in a desiccator.
Weigh the empty crucible to the nearest 0,1 mg. Add the test specimen and immediately weigh again. Place the crucible containing the test specimen in the furnace at room temperature and gradually raise the temperature to 525 °C (about 200 °C/h) in order to burn the sample without it bursting into flames, and to ensure that no material is lost in the form of flying particles. Maintain the ignition temperature of 525 °C for at least 2 h in the case of pulp and board samples and at least 3 h for paper samples. The specimen shall be completely charred as indicated by the absence of black particles. Remove the crucible from the furnace, and cool it to room temperature in a desiccator. Weigh the crucible and content to the nearest 0,1 mg. NOTE If the sample has a very low residue on ignition (for example in the case of so-called ashless grades), it may be necessary to use several portions of the sample which are then ignited consecutively in the same crucible, in order to obtain a total residue of at least 10 mg.