Endress+Hauser Analytik Jena multi EA 5000 - Operation; Preparing the Measuring Cell

Chlorine analysis with the Cl module multi EA 5000
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8.3 Operation
8.3.1 Preparing the measuring cell
Preparing the measuring cell includes the following steps:
¡ Preparing the electrolyte solution
¡ 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.
¡ Wear protective clothing when preparing the electrolyte solution. Work under an ex-
tractor.
¡ 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:
¡ When stored at 4 ±3°C in well-sealed bottles, solutions A and B can be kept for ap-
prox. 6months.