User:Melissa Novy/Notebook/CHEM-572/2013/02/12

Objectives

• Filter 100Ag-LMT (1 week), made on 2013/02/05.
• Create a calibration curve for the determination of Ag⁺ with a silver ion-selective electrode. Solutions of AgNO₃ and KNO₃ made on 2013/02/05 were used.
• Test reserved filtrate solution from 95Ag-LMT (24 h). Please refer to the entry on 2013/02/13 for the data.
• Cells.

100Ag-LMT

• Observations
  • During the week that the solution was stirring, the Laponite formed a thick, medium gray gel with the consistency of Neosporin. Half of the gel was reserved for further testing, and the other half was resuspended in (50:50) H₂O/EtOH and filtered with 42 Whatman paper. The sample was covered with aluminum foil at all times to prevent photodamage to the silver.
• The sample was left to filter overnight. The next day, 100Ag-LMT was brown in color and was still damp. However, its texture changed to a Jello-like consistency. It was scraped from the filter paper and placed in an aluminum dish in an 80°C oven to dry. The filtrate was reserved for further testing.

Ag⁺ Calibration Curve

• Protocol
  1. Beginning with the lowest concentration solution first, place 5 mL in a clean, dry small glass test tube.
  2. Add 100 μL of 5 M KNO₃ as an ionic strength adjustor.
  3. Stir the solution well, then place the electrode in the solution and measure the mV.
  4. Repeat the measurement twice more.
  5. Remove the electrode, rinse it well with deionized water, and blot it dry with Kimwipes.
  6. Repeat steps 1-5 for all solutions

• Notes
  • The calibration solutions were at the following concentrations of Ag⁺: 0.0001 M, 0.0010 M, and 0.0105 M. The electrode was stored in 0.0105 M AgNO³ until next needed.