multi EA 5100
Chlorine analysis with the Cl module 5100
63
8.3
Operation
8.3.1
Preparing the measuring cell
Preparing the measuring cell includes the following steps:
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Preparing the electrolyte solution
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Performing the end point routine
8.3.1.1 The "sensitive" and "high concentration" measuring cells
The measuring cells are similar in function. The "high concentration" measuring cell
works with a larger electrolyte solution volume.
Preparation of the electrolyte
solution
WARNING
Risk of chemical burns
100 % acetic acid (glacial acetic acid), concentrated nitric acid and thymol can cause se-
vere chemical burns. Methanol is a toxic, highly flammable material.
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Wear protective clothing when preparing the electrolyte solution. Work under an ex-
tractor.
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Observe all instructions and specifications in the safety data sheets.
ð
Reagents required: 200 ml acetic acid 100 % (glacial acetic acid), 4 ml concentrated
nitric acid, 4 g gelatin, 1.0 g thymol, 0.3 g thymol blue, 500 ml methanol
}
Solution A:
Fill 500 ml of water into a 1000-ml volumetric flask, add 4 ml of HNO
3
(conc.), care-
fully add 200 ml of acidic acid and top up with water to the marking.
}
Solution B1:
Mix 4 g of gelatin in a beaker with 400 ml of water, allow to swell for 3 hours and
then dissolve whilst heating to 35 to 45 °C.
The excess gelatin will sediment at the bottom of the beaker. Only use the clear su-
pernatant. Filter the solution, if necessary.
}
Solution B2:
Dissolve 1.0 g of thymol and 0.3 g of thymol blue in a beaker with 500 ml of
methanol.
}
Solution B:
After solution B1 has cooled down to 18 to 22 °C, slowly add it to solution B2 while
stirring, transfer into a 1000-ml volumetric flask and top up with water to the mark-
ing.
}
Solution C, finished electrolyte:
Pipette 8 ml of solution B in a 100 ml measuring cylinder and fill with solution A to
100 ml,
or
pipette 40 ml of solution B in a 500 ml measuring cylinder and fill with solution A to
500 ml.
ü
The electrolyte solution is finished.
Storage and shelf life of the electrolyte solutions:
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When stored at 4 ±3 °C in well-sealed bottles, solutions A and B can be kept for ap-
prox. 6 months.
