BS ISO 17197:2014 pdf free

BS ISO 17197:2014 pdf free.Dimethyl ether (DME) for fuels一Determination of water content一Karl Fischer titration method
Add enough solvent to the clean, dry tration vessel to cover the electrodes. The volume of solvent depends on the size of the titration vessel. Seal all openings to the vessel and start the magnetic stirrer for a smooth stirring action. Turn on the indicating circuit and adjust the instrument to give a reference end point.
For the volumetric technique, standardize the Karl Fischer reagent with water by one of the following methods.
一From a water-filled pipette or syringe previously measured with mass to the nearest 0,1 mg, add 1 drop of water (about 20 mg) to the sample solvent at end-point conditions and measure the mass of the syringe. Record the mass of the water added. Titrate the water with Karl Fischer reagent added from the pipette or syringe until a steady end point is reached for at least 30 s. Record to the nearest 0,01 ml the volume of the Karl Fischer reagent needed to reach the end point.
一Filla 10 μl syringe with water taking care to eliminate air bubbles, wipe the needle with tissue paper to remove any residual water from the needle, and accurately determine the mass of syringe plus water to 0,1 mg. Add the contents of the syringe to the sample solvent in the cell which has been adjusted to the end point ensuring that the tip of the needle is below the surface of the sample solvent. Reseal the vessel immediately. Remove any solvent from the needle by wiping it with tissue paper and measure the mass of the syringe to 0,1 mg. Titrate the water with Karl Fischer reagent as in 4.2 or 4.3.
Duplicate values of water equivalence should agree within 2 % relative. If the variation between the two titrations is greater than 2 % relative, discard the contents of the titration vessel. Introduce a further portion of sample solvent into the vessel and repeat the standardization procedure. If the titrations for two further portions of water still vary by more than 2 %, it is likely that either the Karl Fischer reagent or the sample solvent, or both, have aged. Replace these with fresh reagents and repeat the procedure for calibration and standardization.BS ISO 17197 pdf free download.