[I-] by Precipitation Titration
- Prepare 25 - 30 mL 50 mM KI Stock Solution (store in 50 mL Falcon tube)
- Prepare 50 mL 75 mM AgNO3 Solution
- Be very precise with your measurements (use Rm 205 balance)
- Use volumetric flask
- Store in Black 50 mL Falcon tube
- Prepare 100 mL 10 mM NH4SCN Stock Solution (store in Falcon tubes)
- NH4SCN Standardization
- Add 3 mL 1 M HNO3 and 2 mL AgNO3 to 10 mL DI H2O
- Add 200 μL Ferric alum indicator
- Titrate with your NH4SCN solution
- Your solution should turn red around 15 mL
- KI Standardization
- Add 3 mL 1 M HNO3 and 1 mL KI to 10 mL DI H2O
- Add 2 mL AgNO3 and swirl to complete precipitation
- Add 200 μL Ferric alum indicator
- Titrate with your NH4SCN solution
- Your solution should turn red around 10 mL
- [I-] for dialysis
- Follow the same procedure as your KI standardization
- Note that your limit of detection will be based on how small a volume you can read (0.1 mL = 1 mM LOD)
- You may want to try a new NH4SCN solution (more dilute) for smaller concentrations.
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