Expert: John Franceschini - 2/25/2010

Question
Hi John,
I'm wondering if it's possible to derive the concentration of a KMnO4 solution by measuring it's specific gravity. One supplier on the net quotes 1.020 g/mL for a 3% solution and another quotes 1.039 for a 6% solution. Do you know where I could find find the complete SG curve, and how accurate would this method be?

Thanks!
James

Answer
You can only use the SG if the solution is pure Potassium Permanganate and contains no other chemicals- even then it is a very inaccurate way to do this. The solution should be titrated against known Sodium Oxalate or equivalent to get an accurate result.