DRAFT: This module has unpublished changes.
- 10 Test Tubes, 10-mL
- Test Tube Rack
- Pipet, graduated, 10-mL
- Rubber Bulb
- Pipet, plastic (7), 1-mL
- Beaker, 250-mL
- Evaporating Dish
- Stirring Rod
- Hot Plate
- 6 M Sodium Hydroxide, 20 mL
- 6 M Ammonia, 20 mL
- 0.1 M Potassium Chromate, 20 mL
- 6 M Hydrochloric Acid, 20 mL
- Dimethylglyoxime (DMG) Reagent, 5 drops
- 0.2 M Potassium Ferrocyanide, 2 mL
- 3 M Sulfuric Acid, 3 mL
- 3% Hydrogen Peroxide, 2 mL
- Unknown Cation Solution #1, 20 mL
- Unknown Cation Solution #2, 20 mL
- Deionized Water
- Masking Tape
- Gathered equipment. Cleaned test tubes. Labeled test tubes with masking tape and marker, and placed them within test tube rack.
- Filled the 250 mL beaker with deionized water, and heated it to 80º C.
- Measured 1 mL of the unknown solution into an evaporating dish. Added 2 mL of 6 M Sodium Hydroxide. (Note that the experiment has been altered from the book at the instruction of Kadar and to the TAs, to accommodate the lack of litmus paper.) Smelled to determine if the solution contains ammonia. Repeated with the second unknown solution.
- Pipetted 2 mL of unknown solution to a test tube. Added 3 drops of 6 M Hydrochloric Acid. If precipitate forms, continued adding HCl in excess, to ensure that all precipitate forms. If no precipitate forms, save solution for procedure 6. Centrifuged to separate precipitate from solution, before adding more HCl to ensure that all precipitate has formed. Saved the supernatant for procedure 6, and the precipitate for procedure 3.
- Continuing from procedure 2, using precipitate from procedure 2. Added 4 mL of deionized water to the precipitate. Heated the test tube for several minutes in the hot water bath. Centrifuge the test tube to separate the supernatant from remaining solids. Saved supernatant for procedure 5. Saved the precipitate for procedure 4.
- Continuing from procedure 3. Add 10 drops 6 M ammonia solution to the precipitate from procedure 3. Stir, then add HCl drop by drop until a precipitate starts forming, or the solution becomes acidic.
- Continuing from procedure 3. Divide the supernatant into two test tubes. Added several drops of 3 M Sulfuric Acid. Added several drops of Potassium Chromate to the other, then stirred.
- Continuing from procedure 2. Added 6 M NaOH to the supernatant from procedure 2 until precipitation ceases, then add 0.5 mL excess, to ensure that all precipitate has formed. Use the centrifuge to separate the supernatant from the precipitate. Save supernatant for procedure 11. Saved precipitate for procedure 7.
- Continued from procedure 6. Added 3 mL of 6 M ammonia, and stirred. Separated the supernatant from the precipitate, via the centrifuge. Saved supernatant for procedure 10. Saved precipitate for procedure 8.
- Continued from procedure 7 Added 1 mL of 3% Hydrogen Peroxide solution to the procedure from procedure 7. Stirred, then heated the sample with the water bath until it ceased generating gas. Added 3 M Sulfuric Acid until the mixture became acidic. Separated the supernatant from the precipitate, and saved it for procedure 9.
- Continued from procedure 8. Added 2 drops of 0.2 M Potassium Ferrocyanide to the solution from procedure 8.
- Continued from procedure 7. Added 1 drop of 6 M HCl, then 5 drops of Dimethylglyoxime reagent to the solution from procedure 7.
- Continued from procedure 6. Neutralized the solution from procedure 6 by adding 3 M Sulfuric Acid until pH is balanced. Added 2 more drops of 3 M Sulfuric Acid. (Note: Normally the supernatant would be saved for procedure 12, however this lab was altered so as not to include Procedure 12. It has been included for the sake of completeness of concept.)
- (not performed, due to change in experiment) Continued from procedure 11. Would have added 2 drops of Aluminon dye to the solution from procedure 11. Would have added 6 M Ammonia, drop by drop while stirring until the solution turns basic.