ISO 20336:2017 pdf free

ISO 20336:2017 pdf free.Solid mineral fuels一Determination of total sulfur by Coulomb titration method
In the presence of the catalyst, a weighed sample is combusted at 1 150 °C in a stream of purified air.The sulfur oxides are formed and dissolved in the electrolytic solution. The sulfur dioxides are titrated by the iodine and bromine librated from the electrolysis of the potassium iodide and potassium bromide solution. The quantity of the electricity consumed by electrolysis is integrated and used to calculate the content of sulfur dioxides. The instrument is calibrated with certified reference materials.The percentage of total sulfur in the sample is calculated according to the sulfur dioxides content and the prior calibration.
Assemble tube resistance furnace (6.2) with a combustion tube (6.2), electrolytic cell (6.3),magnetic stirrer (6.3), coulomb integrator (6.4), the program controller (6.5), purified air stream supply system (6.6). The combustion tube, stopcock and electrolytic cell should be connected in glass to glass closely and seal them with the silicone rubber sleeves.
Switch on the pump and adjust the rate of suction to 1 000 ml/min, then close the stopcock between the electrolytic cell and the combustion tube. If the rate of suction drops down under 300 ml/min, it indicates that all of parts and joints of the instrument are gas tight. Otherwise, check for the leaks in the system.
Check the instrument to make sure that it is in the normal condition before calibration. Determine the sulfur content of the CRMs of coal or coke in accordance with the procedures specified in 8.4. Run a minimum of three times (in triplicate) for every sample. Take the mean value of the replicates as the determined value for sulfur. The replicate results shall agree within the repeatability limit specified in 10.1, if not, check the instrument and repeat the calibration tests.
Verify the calibration by analyzing another (1 to 2) appropriate CRMs of coal or coke according to the procedures described in 8.4. If the determined result is within acceptable repeatability limits with the CRM, the calibration is valid; otherwise, the reason for the deviation should be investigated, corrected and the instrument recalibrated.
Need to add uncertainty (as a variance) of CRM with repeatability (as a variance). The square root gives the necessary limits. It should be recognized the calibration will be dominated by the CRM with the highest uncertainty.ISO 20336 pdf free download.