Note d'application Titration des chlorures

Chloride.docx 1/4 SI Analytics -Appli cation report Titration Titration of Chloride Description The determination of the chloride content is done by titration with silver nitrate solution 0.001 - 0.1 mol/ l. This determination is not always easy, since first the chloride has to be released from the sample. This determination is suitable for aqueous or water soluble samples with chloride contents below 1 ppm up to 100% . For very small chloride contents well below 10 ppm, it may be advantageous to carry out the titration in acetic acid with a 0.001- 0.002 mol / l silver nitrate solution (dissolved in 90% acetic acid). The calculation is made as mg / l chloride. Instruments Titrator TL 5 000 or higher Electrode AgCl 62 or AgCl 62 RG Cable L1A Stirrer Magnetic stirrer TM 235 or similar Lab accessory Gla ss beaker 1 50 ml Magnetic stirrer bar 30 mm Reagents 1 Silver nitrate solution 0.1 mol/l 2 Nitric acid 4 mol/l 3 Polyvinylalkohol – solution 0.5% 4 Electrolyt e solution L2114 (KNO 3 2 mol/l + KCl 0.001 mol/l) for AgCl 62, Ag 6280 5 Distilled Water All reagents should be of analytical grade or better. Chloride.docx 2/4 Titration procedure Reagents The titer determination of the AgNO 3 solution is carried out as d escribed in the application report "Titer determination of AgNO 3". Polyvinyl alcohol - solution 0.5% 0.5 g of polyvinyl alcohol are dissolved in 100 ml of distilled water. The addition of polyvinyl alcohol is recommended for high chloride /salt concentrations. It avoid s the agglomeration of the silver chloride. Cleaning of the electrode The electrode is rinsed wit h distilled water. The electrolyte solution L2114 is suitable for storage. T he AgCl 62 RG or Ag 62 RG can be stor ed in water. Sample preparation The sample is pipetted into a 150 ml beaker and filled up to about 80 ml with distilled water. 0.5 ml 4mol/ l HNO 3 and 0.5 - 1 ml of the polyvinyl alcohol solution are added. The titration is done with 0.1 mol/l AgNO 3 solution to an equivalence point. The consumption should be about 5 - 15 ml. The titration can be carried out with samples with chloride contents of a few ppm - 100%, but the amount of sample has to be adjusted. Sample amount for titration with 0.1 mol/l AgNO 3 Chloride content [%] Sample [g] < 0.1 > 10 0.1 – 1 1 – 10 1 – 10 0.1 – 0.2 10 – 50 0.05 – 0.1 50 - 100 0.05 Chloride.docx 3/4 Titration parameter Sample titration Default method Chloride mg/l Method type Automatic titration Modus Dynamic Measured value mV Measuring speed / drift User defined Minimum holding time 3 s Maximum holding time 15 s Measuring time 3 s Drift 10 mV/min Initial waiting time 0 s Dynamic average Max step size 1.0 ml Slope max ml 10 Min. step size 0.02 ml Slope min. ml 120 Damping none Titration direction increase Pretitration off Delay time 0 s End value off EQ On (1) Slope value 150 Max. titration volume 50 ml Dosing speed 100% Filling speed 30 s When titrating very low levels of chloride or titrating in glacial acetic acid, the minimum waiting time should be s et to 6 s and the drift to 5 mV /min. In this case, the dynamics should also be set to flat. For some samples it may happen that the titration curve is very flat and the titrator does not stop the titration at the EQ. In this case, the slope val ue for the EQ should be reduced. Chloride.docx 4/4 Calculation: ������������ [ ���� /��] = ( �� ? ���� 1) ? �� ?�� ?��1 �� ?��2 B 0 Blank value EQ1 Consumption of titrant at first Equivalence point T WA Actual concentration of the titran t M 35.45 Molecular weight of chloride W man sample weight in g F1 1000 Conversion factor F2 1 Conversion factor If the calculation value is not mg/l chloride, but mg/l NaCl, then M is set to the molar mass of NaCl 58.44 g/ mol. Any questions ? Please contact the application team : Xylem Analytics Germany Sales GmbH & Co. KG, SI Analytics Hattenbergstraße 10 D -55122 Mainz, Germany Telefon: + 49 6131 66 5126 Fax: + 49 6131 66 5101 E -Mail: titration@ si-analytics.com Xylem Analytics Germany Sales GmbH & Co. KG · Hattenbergstr. 10 · D -55122 Mainz · Germany Telefon: +49 6131.66. 5111 · E -Mail: Info.si -analytics@Xyleminc.com · www.si- analytics.com Alle Namen sind eingetragene Handelsnamen oder Warenzeichen der Xylem Inc. oder eines seiner Tochterunternehmen. Technische Änderungen vorbehalten. © 2018 Xylem Analytics Germany Sales GmbH & Co. KG.