BS ISO 17197 pdf free download

BS ISO 17197-2014 pdf free download.Dimethyl ether (DME) for fuels – Determination of water content – Karl Fischer titration method.
6 Sampling and sample handling
6.1 Samples shall be taken as described in ISO 29945.
6.2 Test Specimen: the aliquot obtained from the laboratory sample for analysis by this test method.
Once drawn, use the entire portion of the test specimen in the analysis.
6.3 Select a test specimen size from 10 g to 20 g.
7 Preparation of apparatus
7.1 Follow the manufacturer’s directions for preparation and operation of the titration apparatus.
7.2 Seal all joints and connections to the vessel to prevent atmospheric moisture from entering the apparatus.
7.3 Add the sample solvent into the titration vessel to the level that is recommended by the manufacturer. Prepare the Karl Fischer reagent as described in 42 or 43.
For coulometric titration, add the Karl Fischer anode solution to the anode (outer) compartment. Add the solution to the level recommended by the manufacturer. Add the Karl Fischer cathode solution to the cathode (inner) compartment. Add the solution to a level 2 mm to 3 mm below the level of the solution in the anode compartment.
7.4 Turn on the apparatus and start the magnetic Stirrer for a smooth stirring action. Allow the residual moisture in the titration vessel to be titrated until the end point is reached. Do not proceed beyond this stage until the background current (or background titration rate) is constant and less than the maximum recommended by the manufacturer of the instrument.
7.5 Install the needle to the double-valve gas cylinder. Stick the needle of the cylinder to the titration flask and fix the cylinder. The needle shall be rolled with tissue paper or threaded into a silicone rubber plate to prevent dew condensation water from mixing into the titration flask
7.6 Open the liquid valve of the sample cylinder slowly and adjust the gas flow rate in the range of
0,5 g/min to 2,0 g/min. Be sure that the gas doesn’t generate foam or overflow. The needle shall be below
the liquid surface, with at least 3,0 cm to allow the water content in the bubbled gas to be extracted in the
solvent.
7.7 Allow the residual moisture in the titration vessel to be titrated until the end point is reached again. The system now is ready for sample titration. Disconnect the sample cylinder and measure the mass and record as the “initial sample mass’
8 Calibration and standardization
8.1 Standardize the Karl Fischer reagent at least once daily.
8.2 Add enough solvent to the clean, dry titration 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.
8.3 For the coulometric technique, follow the manufacturer instructions for instrument calibration.
8.4 For the volumetric technique, standardize the Karl Fischer reagent with water by one of the following methods.
— 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.
— Fill a 10 .l 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 42 or 4,3.
8.5 Calculate the water equivalence of the Karl Fischer reagent using Formula (1).
F=W/T (1)
where
F is the water equivalence of the Karl Fischer reagent, in mg/mi;
W is the water added, in mg;
T is the reagent required for titration of the added water, in ml.
8.6 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.
8.7 Determine and record the mean water equivalence value.
9 Procedure
9.1 Add newly made solvents to the anode and cathode compartments of the titration vessel and bring the solvent to end-point conditions as described in Clause 6.
9.2 Add the dimethyi ether test specimen to the titration vessel using the procedures described in ,3 and A. considering the following.
— Estimate the time that is required to consume the desired sample mass described in 6.3.BS ISO 17197 pdf download.