200 ml sample (measuring cylinder; for chlorine concentrations > 2 mg/l use less sample and fill up with dist. water to 200 ml) are filled into a 250 ml beaker. Add 1 ml KI solution and 1 ml buffer solution pH = 4.0 and titrate with the phenylarsine oxide to an equivalence point (potentiometry) or μA endpoint (amperometry)
Titrator: TL 6000-M2/20 or TL 7000-M2/20 consists of
? Basic device
? Magnetic stirrer TM 235
? 20 mL exchange unit WA 20, with brown glass bottle for titrant complete
? pH combination electrode with integrated temperature sensor (A 162 2M-DIN-ID, N 1052 A, BL 18…)
This method is used for the quantitative determination of total hardness in drinking water.
The total hardness is the sum of calcium and magnesium hardness. It is possible to titrate the Ca- and Mg hardness with a Ca-ISE electrode as two equivalence points (EQs) in one titration. But it is recommended to use the more robust Cu-ISE for the determination of total hardness