The authoritative public forum
  for Metal Finishing since 1989
-----

Titration procedure for permanganate

We are using a solution of 10% caustic soda ⇦liquid caustic soda in bulk on Amazon [affil link] and 4% potassium permanganate ⇦this on eBay or Amazon [affil links] to desmut stainless steel. Does anyone know a titration procedure to analyse th permanganate in this solution?

Fred P. Hayduk
- Wadsworth, OH, U.S.A.
2006

---

I find no established procedure for what you're trying to analyze. So, I'm winging it. If someone else who does this comes forward with a test procedure, ignore me and listen to them. I am not sure if you are putting current through this solution as part of your process. If you are, you may get hexavalent chromium in the process solution. That will lead to a positive interference in the method that follows.

Take a sample of your solution and filter it. Transfer 5 ml to an Erlenmayer flask, add about 100 ml of water and 25 ml glacial acetic acid ⇦this on eBay or Amazon [affil links] . Now add about 1 g potassium iodide. Iodine will be liberated. Titrate with 0.1N sodium thiosulphate ⇦this on eBay or Amazon [affil links] to a straw yellow color, add starch indicator, then continue titrating to a colorless endpoint.

The calculation of the result is straight forward Chem 101 stoichoimetry. I leave it as an "exercise for the student."

Good luck.

Dave Wichern
Consultant - The Bronx, New York
2006

---

I don't have the procedure handy, but permanganate solutions are used in the printed circuit industry for drill smear removal. Any of the suppliers to the PCB fabrication community would have this analysis.

James Totter, CEF
- Tallahassee, Florida
2006

---

Mr Hayduk..We use a 100g/l Caustic and 60g/l Permanganate solution similar to yourself to desmut steel forgings. Try this procedure which I use.
Take a sample from the bath and immediately filter through a sintered glass filter. pipette [pipettes on eBay or Amazon [affil links] 10 mls of the hot filtered solution into a 100 ml beaker [beakers on eBay or Amazon [affil links] containing 50 mls of saturated Barium Hydroxide solution. Shake well and filter through a sintered glass filter. Pipette 25 mls of the filtrate into a 250ml conical flask, add 40 mls of 1.0N sulfuric Acid and 50 mls of distilled water. Heat to 70-80 °C and titrate with 0.2N Oxalic Acid to the absence of the brown precipitate (MnO2 - manganese dioxide) produced during the initial stages of the titration.A small quantity of slightly grey or pink precipitate will remain (Barium Sulphate). Let the volume required to dissolve the last traces of brown precipitate be V1 mls.
Calculation: g/l Potassium Permanganate = 1.517 x V1 mls.

Hope this helps and good luck!

Nigel Gill, BSc MIMF MRSC
Aerospace - Glasgow, Scotland
2006