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