Iron Content Test for Nitric Acid Passivation Baths

A. Dear Kierra :
Peace be upon you
You can use the next procedure,
1- take a known weight from the bath W(15-25 gm).
2- add 25 conc. HCl, then boil in w.p. for nearly one hour.
3-add 400 d.w., then 10 ml. cons H2SO4.
4- titrate against KMnO4 0.1 N, the color change from colorless to pink after X ml. titrant.
Calculation:
Fe % = Xml. of titrant*0.558/W gm

A. Are you working to a spec that limits the iron concentration?
If not, what will the concentration tell you?
Passivation baths dissolve very little iron.
Iron in a nitric solution is green and nitric acid is cheap.
If the solution is green - change it.

Salah, thank you so much for your response ... I have really been having a hard time trying to figure this simple method out! You have really saved my from any further headaches :)

Geoff, thanks for responding also, but I needed the method more for control measures than just evaluating solution color. I'm trying to follow our most stringent specs as well as AMS2700 [affil link] which states the iron content should be no more than 2% by weight. This will be most helpful in the event of an audit :)

I appreciate you both!
Warmest Regards,
Kierra

A. Hi Dan. We'd probably have to see it used in context to know for sure, but I think it will mean "weight percentage" / percentage by weight.

Regards,