Mettler Toledo GA42 Operations Instructions download pdf (Page 33)

METTLER TOLEDO DL36 31

Maintanance and servicing

2. Cleaning with chromic acid (if foreign matter has collected on the membrane or the

platinum surface).

– Perform the first 3 steps as described under point 1.

– Add approx. 10 mL chromic acid and place in a beaker.

– Fill the beaker with chromic acid until the level in the cathode is reached.

– Allow to stand overnight.

– Empty the inner burette and wash the cathode five or six times with pure water until the

yellow color disappears (rinse chromic acid from the membrane).

– Rinse with methanol and dry.

Note: Chromic acid cleaning solution: dissolve approx 1.5 g potassium dichromate in

100 mL concentrated sulfuric acid.

3. Drying

– Place the inner burette in a vacuum drying oven for at least two hours (temperature no

higher than 50 °C).

If no vacuum drying oven is available, you can use a hair dryer (blow warm air over the

membrane of the inner burette until it is dry) or a desiccator.

11.9 Measures for long-term storage

We recommend cleaning the titration cell, disassembling it, drying the parts and then storing

them in a desiccator.

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Mettler Toledo GA42 Operations Instructions Page 33