Chlorine analysis with the Cl module 5100
multi EA 5100
64
¡
The finished electrolyte solution (solution C) can be kept for approx. 30 days if kept
in a well-sealed glass container at 20 to 25 °C.
Performing the end point rou-
tine
An end point routine is necessary after every electrolyte change. The end point routine is
used to adjust the electrolyte to the optimal operating range of the measuring cell. The
operating point of the measuring cell is: 1500 to 5000 Counts .
}
Start the end point routine via the System |End point routine menu item.
}
Remove the olive from the lid of the measuring cell. Dose the HCl solution directly
into the measuring cell when instructed to by the software.
"sensitive" measuring cell: 200 µl of 0.01 N HCl
"high concentration" measuring cell: 200 µl of 0.1 N HCl
}
Directly after dosing, activate the end point routine by clicking on [OK].
}
The End point routine status is displayed in the Status analyzer window during this
routine. After the end point routine, the Stand-by titration and the current indicator
value is displayed.
ü
The system is ready for measurements.
The determined operation point of the combined electrode is displayed in the System |
Component test menu item in the Chlorine tab.
Protecting the combined elec-
trode
Observe the following to protect the combined electrode against unnecessary wear:
¡
Always add fresh electrolyte to the measuring cell before the end point routine.
¡
Do not carry out the end point routine several times in a row.
8.3.1.2 The "high sensitive" measuring cell
Preparation of the electrolyte
solution
Measurements with the "high sensitive" measuring cell require an electrolyte solution.
The electrolyte solution is also used as a bridge electrolyte for the reference electrode.
WARNING
Risk of chemical burns
100 % acetic acid (glacial acetic acid) can cause severe chemical burns. Gases may de-
velop during shaking.
¡
Wear protective clothing when preparing the electrolyte solution. Work under an ex-
tractor.
¡
Observe all instructions and specifications in the safety data sheet.
ð
Reagents required: 800 ml acetic acid 100 % (glacial acetic acid), 2.7 g sodium ac-
etate p.a. (CH
3
COONa), anhydrous
}
Dilute 2.7 g of sodium acetate in 200 ml of ultrapure water in a 1-liter volumetric
flask.
}
Carefully add 800 ml of glacial acetic acid. Keep moving the flask while pouring the
acid. Carefully shake the mixture.
NOTICE! Do not exceed the specified amounts of water and glacial acetic acid. Do
not fill the flask up to the 1-liter mark (volume contraction).
Performing the end point rou-
tine
The end point routine is used to set the electrolyte to the optimum operating point of
the sensor electrode within the operating range of the titration cell.
¡
Operating range: 1000 to 10000 Counts
¡
Optimal operation range: 3000 Counts
