ISO 1994:1976 pdf download.Hard coal一Determination of oxygen content
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.
Dissolve 5g of platinum in aqua regia and evaporate the solution to near dryness. Add 5 ml of hydrochloric acid,ρ 1,18 g/ml, and again evaporate to near dryness. Continuefrequent 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.
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 silica 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 untill 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 neutrality 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.ISO 1994 pdf download.