How to calculate Mn Average Oxidation States by titration method?
Please look at the following below links which may help you in your analysis:
https://shamra.sy/uploads/documents/document_07ed58de7d38f5c53b4a49666c6b6b1f.pdf
https://pubs.rsc.org/-/content/articlelanding/2017/ay/c6ay02472f/unauth#!divAbstract
Thanks
Firstly, you should know the amount of the Mn, by means like ICP or other method.
Then used titration method, refer to the following steps:
2.3. Elemental analysis and oxalic acid–permanganate back titration method
The elemental analysis of the samples was performed as follows: 0.02 g of sample was dissolved in 50 mL 0.02 mol L−1hydroxylamine hydrochloride. The contents of K and Na were measured using a flame spectrophotometer.
The Mn AOS of vernadite, hausmannite and acid birnessite was determined with the oxalic acid–permanganate back titration method as a comparison.16 0.2 g of the manganese minerals was dissolved in 5 mL of 0.5 mol L−1 H2C2O4 and 10 mL of 1 mol L−1 H2SO4 to reduce the Mn oxide sample to Mn2+ solution. The excess C2O42− was back-titrated with standardized KMnO4solution at 75–85 °C to obtain the oxidation number of Mn with a valence higher than two, i.e. Mn3+ and Mn4+.
The total Mn content was determined with the formaldoxime colorimetric method.34 0.01 g of the sample was dissolved in 50 mL of 0.01 mol L−1 hydroxylamine hydrochloride. After the solution was diluted 10 times, 2 mL sample solution mixed with 2 mL buffer and 2 mL formaldoxime solution was added to a 25 mL colorimetric tube followed by the addition of 2 mL EDTA-2Na. Then, the absorbance of the solution was determined at 450 nm after 20 min. The Mn AOS was calculated according to both the total Mn content and the titration result. The procedure was repeated three times for each sample.
details are in paper of DOI: 10.1039/C6AY02472F
Zhu, Y., Liang, X., Zhao, H., Yin, H., Liu, M., Liu, F., & Feng, X. (2017). Rapid determination of the Mn average oxidation state of Mn oxides with a novel two-step colorimetric method. Analytical Methods, 9(1), 103-109.
This paper contains two methods back titration and colorimetric method
https://pubs.rsc.org/en/content/articlelanding/2017/ay/c6ay02472f#!divAbstract
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