multi X 2500
AOX determination
59
6.2.2
Preparing the measuring cell
The preparation of the measuring cell includes the following steps:
Preparation of the electrolyte solution
Execution of the end point routine
The standard version of the analyzer is equipped with the measuring cell "sensitive". It
has the same function as the optional measuring cell "high concentration" which works
with larger volumes of electrolyte solution.
WARNING
100 % acetic acid (glacial acetic acid), concentrated nitric acid and thymol can cause
severe chemical burns! Methanol is a toxic, highly flammable material.
Wear the appropriate protective clothing when preparing the electrolyte solution!
Observe all instructions and specifications in the safety data sheets!
200 ml of acetic acid c = 100 % (glacial acetic acid)
4 ml of concentrated nitric acid
4 g of gelatin
1.0 g of thymol
0.3 g of thymol blue
500 ml of methanol
The electrolyte solution for the measuring cells "sensitive" and "high concentration" is
prepared as follows:
1.
Solution A:
Fill 500 ml of water into a 1000-ml volumetric flask, add 4 ml of HNO
3
(conc.),
carefully add 200 ml of acidic acid and top up with water up to the marking.
2.
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 supernatant.
3.
Solution B2:
Dissolve 1.0 g of thymol and 0.3 g of thymol blue in a beaker with 500 ml of
methanol.
4.
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 up to the
marking.
5.
Solution C – finished electrolyte:
Preparation of the
electrolyte solution
Reagents required:
Preparation of the
electrolyte solution
