User:Douglas M. Fox/Notebook/AU CHEM-571 F2011 Lab Support/2014/10/08

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[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
    1. Add 3 mL 1 M HNO3 and 2 mL AgNO3 to 10 mL DI H2O
    2. Add 200 μL Ferric alum indicator
    3. Titrate with your NH4SCN solution
    4. Your solution should turn red around 15 mL
  • KI Standardization
    1. Add 3 mL 1 M HNO3 and 1 mL KI to 10 mL DI H2O
    2. Add 2 mL AgNO3 and swirl to complete precipitation
    3. Add 200 μL Ferric alum indicator
    4. Titrate with your NH4SCN solution
    5. 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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