There are different methods for determining manganese:
- Atomic absorption spectroscopy (AAS): High-precision determination of Mn²⁺.
- Oxidimetric titration with KMnO₄: direct determination by redox reaction.
- Complexometric titration with EDTA: Precise determination by chelation.
- Spectrophotometry: Color complex formation with suitable reagents.
Detailed titration of manganese with potassium Permanganate (KMnO₄)
1. Principle of the method
Manganese ions (Mn²⁺) are oxidized by potassium Permanganate (KMnO₄). In acidic solution, Mn²⁺ reacts with KMnO₄ according to the equation:
The end point of the titration is identified by the faint pink color of the unreacted Permanganate.
2. Chemicals
- 0.01 mol/L potassium Permanganate solution (KMnO₄)
- Sulfuric acid (H₂SO₄), 1 mol/L
- Distilled water
3. Experimental setup
Required equipment:
- Burette (25 mL, division 0.1 mL)
- Erlenmeyer flask (250 mL)
- Pipette (10 mL)
- Magnetic stirrer
4. Implementation
- Pour 10 mL of the nutrient solution into a 250 mL Erlenmeyer flask.
- Add 10 mL of 1 mol/L sulfuric acid.
- Titrate with 0.01 mol/L KMnO₄ until a faint pink color persists.
5. Calculation of manganese concentration
The concentration of Mn²⁺ is calculated using the formula:
6. Example calculation:
- Potassium permanganate concentration: 0.01 mol/L
- Consumed volume: 7.2 mL (0.0072 L)
- Sample volume: 50 mL (0.050 L)
Conclusion
Redox titration with KMnO₄ is a precise method for the quantitative determination of manganese in nutrient solutions.
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