ISO 1994:1976 pdf download – Hard coal – Determination of oxygen conten
3 PRINCIPLE
The sample is dried at 105 to 110 °C in a stream of nitrogen and then pyrolysed under conditions in which the organic matter leaves an oxygen-free char. The volatile products, containing the organically bound oxygen and also water and carbon dioxide from any mineral matter, are decomposed with either pure carbon or platinized carbon to convert the oxygen to carbon monoxide. The carbon monoxide is oxidized to carbon dioxide and determined by a titrimetric[4] or a gravimetric procedure.
adding 5 ml portions of hydrochloric acid and evaporating to near dryness until nitrous fumes are no longer evolved and then evaporate the solution to dryness. Moisten the residue with 2 ml of hydrochloric acid and add sufficient water to dissolve the platinic chloride. Add 5 g of ignited carbon that contains not more than 0,01 % of ash (see 4.2.1) and more water, if necessary, to form a paste. Mix thoroughly and evaporate to dryness on a water bath, mixing frequently with a glass spatula or rod to ensure a homogeneous product. Dry the resulting cake at 150 °C. Break the cake into pieces and insert them into a 10 to 12 mm internal diameter sllica tube. Pass dry nitrogen (4.1) through the tube and heat the tube slowly to red heat, in stages, using a Bunsen burner. Begin heating the tube at the inlet end and when this is hot, move the burner very slowly along the tube until all the contents have been ignited. Replace the nitrogen with hydrogen and heat again in a similar manner in a stream of hydrogen. Repeat heating in hydrogen in this way until the effluent gas is free from hydrogen chloride as shown by its neutralty to litmus. Replace the hydrogen with nitrogen and allow the contents of the tube to cool to room temperature in a stream of nitrogen. Remove the platinized carbon, and crush and sieve the product carefully to obtain the maximum yield of 0,7 to 2,0 mm material.
frequent shaking, 25 ml of sulphuric acid, ρ 1,84 g/ml. Then add, in about 1g portions, 30 g of finely ground iodine pentoxide; after the addition of each portion of iodine pentoxide, thoroughly mix the contents of the flask by shaking. Close the flask with a socket that has a tube . through which the flask can be evacuated. Immerse the flask to the ground joint in an oil bath at 200。C and evacuate to a pressure less than 5 kPa4) for 2 h. Allow the flask to cool under vacuum and transfer the reagent to a dry glass bottle that has a well ground glass stopper. Store the bottle in a desiccator to prevent the reagent from absorbing moisture.
4.7.2 Anhydro-iodic acid (HI3Og)
If anhydro-iodic acid suitable for the determination of carbon monoxide cannot be obtained commercially, it may be prepared by the following method : Add an excess of iodic acid or iodine pentoxide to a boiling mixture of 3 volumes of nitric acid, p 1,4 g/ml, and 2 volumes of water. Boil the solution with the undissolved excess for 1 h to obtain a saturated solution. Filter the hot solution immediately by suction through a sintered glass filter (pore size 15 to 40 μm). Leave the filtrate to crystallize for a day. Transfer the crystals to a sintered glass Buchner funnel and wash them with cold nittric acid, ρ 1,4 g/ml. Dry the crystals at room temperature, first by aspirating clean air over them for. 1h and then in a desiccator containing dishes of sodium hydroxide and phosphorus(V) oxide.