User:Michael S. Bible/Notebook/571/2014/10/14

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[I-] by Precipitation Titration

  • Prepare 25 - 30 mL 50 mM KI Stock Solution (store in 50 mL Falcon tube)
    • To make this solution, 0.249 g of KI was added to 30 mL of water
  • Prepare 50 mL 75 mM AgNO3 Solution
    • To make this solution, 0.637 g of AgNO3 was mixed with water in a 50 mL volumetric flask
    • 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)
    • To make this solution, 0.07612 g of NH4SCN was mixed with water in a 100 mL volumetric flask
  • 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

Procedure taken from Dr. Fox's Notebook

Data

NH4SCN Standardization

  • Volume required for first titration = 16.0 mL. Second titration = 15.55 mL. Average = 15.78 mL.
    • AgNO3+NH4SCN→AgSCN+NH4NO3
      • Reaction is 1:1
      • 2mL of AgNO3=1.5×10-4 mol
      • 15.75 mL of NH4SCN contain 1.5×10-4mol
      • [NH4SCN]=9.51 mM
  • Concentration of AgNO3 at the lowest saturated concentration:
    • [Ag][SCN]=Ksp where Ksp=1.03×10-12 (at 25ºC)
    • x2=Ksp
    • [Ag] at the lowest saturated concentration=1.01μM


KI Standardization

  • Volume required for first titration = 10.7 mL. Second titration = 10.7 mL. Average = 10.7 mL.
  • KI+AgNO3→AgI+AgNO3+KNO3
  • AgNO3+NH4SCN→AgSCN+NH4NO3
    • 10.7 mL of NH4SCN were required to titrate excess AgNO3. 10.7 mL of

NH4SCN contains =1.0176×10-4mols of NH4SCN

    • 2mL AgNO3 contain 1.5×10-4 mol
    • 1.5×10-4−1.0176-4=4.824×10-5 mol of AgNO3 reacted with KI in a 1:1 reaction
    • 1 mL of KI contains 4.824-5 mol
  • [KI]=48.24 mM

Additional Experimentation Conducted Today

  1. Extracted contents of the HCl Lysozyme dialysis
    1. These were placed into 1.5mL centrifuge tubes for further testing
  2. Created new SDS Page Solutions
    1. Mixed 10 μL 0.6 g/L lysozyme with 10μL SDS-PAGE sample buffer in 1.5 mL centrifuge vial
    2. Mixed 10 μL 0.12 g/L lysozyme with 10μL SDS-PAGE sample buffer in 1.5 mL centrifuge vial
    3. Mixed 10 μL 30:1 Au/lysozyme colloid with 10μL SDS-PAGE sample buffer in 1.5 mL centrifuge vial
    4. Mixed 10 μL 0.12 g/L unknown protein with 10 μL SDS-PAGE sample buffer in 1.5 mL centrifuge vial
    5. Placed in heating block (set at 90 °C) for 5 minutes
    6. Stored in refrigerator overnight
  3. Created a Potassium Phosphate Buffer
    1. The original protocol asked to make the buffer using KH2PO4 and 1M KOH
    2. We opted to use the monobasic and dibasic species of the molecule to obtain the desired pH of 6.24

To make the Potassium Phosphate buffer we used:

  • 0.0839g of K2HPO4
  • 0.2888g of KHPO4




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