7. Maintenance
MKC-710 89
Cleaning with nitric acid (boiling) :
If the color of inner burette or diaphragm does not disappear
When there is a deposition of iodine on the diaphragm or the electrode surface, clean
with 1mol nitric acid (boiling):
1)
Immerse the diaphragm or the electrode surface in nitric acid, and boil with a hot
stirrer.
2)
Drain out the chromate inside the cell, and rinse it with pure water for 2 to 3 times
until yellowish color disappears.
3)
Clean the inner burette with methanol or with alcohol.
4)
Repeat the above steps several times when dirt does not come off.
Caution
When handling this chemical, protect yourself with gloves and
glasses. If it touches your skin, immediately rinse it with running
water.
Caution
Be careful not to burn yourself when using a hot stirrer.
Cleaning with chromic acid mixture
：
When a dirt does not come off
If foreign objects are observed on diaphragm and platinum surface, use chromic acid
mixture instead of methanol for cleaning.
Chromic acid mixture:
1.5g approx. potassium dichromate dissolved in 100mL of concentrated sulfuric acid
Caution
Chromic acid mixture is a very strong oxidizing reagent.
When handling this chemical, protect yourself with gloves
and glasses. If it touches your skin, immediately rinse it
with running water.
1)
Follow the same steps as above for methanol.
2)
Drain out the chromate inside the cell, and rinse it with pure water for 5 to 6 times
until yellowish color disappears.
3)
Clean the inner burette with methanol or with alcohol.
