IS0 4935 : 1989 pdf download – Steel and iron – Determination of sulfur content – Infrared absorption method after combustion in an induction furnace.
5 Apparatus During the analysis, unless otherwise stated, use only ordinary laboratory apparatus. All volumetric glassware shall be class A, in accordance with IS0 385-1, IS0 648 or IS0 1042 as appropriate. The apparatus required for combustion in a high-frequency induction furnace and the subsequent infrared absorption measurement of the evolved sulfur dioxide may be obtained commercially from a number of manufacturers. Follow the manufacturer’s instructions for the operation of the equipment. Features of commercial instruments are given in annex C. 5.1 Micropipettes, 50 pl and 100 pl, limit of error shall be less than 1 1.11. 5.2 Tin capsule, about 6 mm in diameter, 18 mm in height, 0,3 g in mass and approximately 0,4 ml in volume. 5.3 Ceramic crucible, capable of withstanding combustion in an induction furnace. Ignite crucibles in an electric furnace in air or in a current of oxygen for not less than 2 h at 1 100 OC and store in a desic- cator before use. NOTE – For the determination of low sulfur contents it is advisable to ignite crucibles at 1 350 ‘% in a current of oxygen. 8 Sampling Sampling shall be carried out in accordance with IS0 377 or appropriate national standards for iron.
Allow each item of equipment to stabilize for the time recom- mended by the equipment manufacturers when the main supply is switched on after being out of action for any length of time. After cleaning the furnace chamber and/or changing filters or after the equipment has been inoperative for a period, stabilize the apparatus by burning several samples of similar type to the samples to be analysed prior to setting up for analysis. Flush oxygen through the apparatus and adjust the instrument controls to give a zero reading. If the instrument used provides a direct reading in percentage sulfur, adjust the instrument reading for each calibration range as follows. Select the certified reference material with a sulfur content close to the maximum sulfur content in the calibration series, measure the sulfur content of the certified reference material in the same manner as specified in 7.4. Adjust the reading of the instrument to the certified value. NOTE – This adjustment shall be made before the calibration as specified in 7.5. It cannot replace or correct the calibration. 7.2 Test portion Degrease the test sample by washing in a suitable solvent (4.3). Evaporate the last traces of the washing liquid by heating. Weigh, to the nearest 1 mg, 1 g of the test sample for sulfur contents less than 0,04 % (m/m) and 0,5 g for sulfur contents greater than 0,04 % (m/m). NOTE – The mass of the test portion may be dependent on the type of instrument used. 7.3 Blank test Prior to the determination, carry out the following blank tests in duplicate. Transfer a tin capsule (5.2) to a ceramic crucible (5.31, press the tin capsule lightly against the bottom of the crucible. Add the same quantity of the pure iron (4.2) as the test portion (7.2) and I,5 g + 0,l g of the accelerator (4.5).