Methods:

 

Set Up

1. Place at least 10 clean test tubes in a test tube rack.

2. Organize a plan for labeling test tubes.

3. Number of unknown solution: 2

4. Prepare a hot water bath (approximately 80 degrees C).

 

Procedure 1 (Detection of ammonium ion)

1. Measure 1 mL of the unknown solution into an evaporating dish

2. Add approximately 2 mL of 6 M NaOH with a plastic pipet and cover with a watch glass with a piece of moist red litmus paper attached.

3. Observe the litmus paper for a color change from red to blue, indicating the presence of ammonia.

 

Procedure 2(Separation of silver and lead as chlorides)

1.With a new clean pipet transfer 2 mL of the unknown to a test tube.

2.Add 2 to 3 drops of 6 M HCl. If a precipitate forms, continue adding 6 M HCL solution drop by drop while stirring until the precipitate stops forming. If no precipitate forms salve the solution for procedure 6.

3. Centrifuge the mixture in the test tube and then add one drop of 6 M HCl.

4. If no additional precipitate appears, pour the supernatant into another test tube.

5. If more precipitate forms, repeat the last two steps until no new precipitate forms.

6. Label the samples and save the supernatant for Procedure 6, and use the precipitate for procedure 3.  There was no precipitate therefore procedure 6 was done next.

 

Procedure 6(Precipitation of nickel, manganese and iron ions as hydroxides)

1. Add 6 M NaOH to the supernatant from Procedure 2 until precipitation is complete.

2. Add 0.5 mL more of the NaOH and stir.

3. Separate the supernatant from any precipitate. Save the supernatant for Procedure 11 and use the precipitate for procedure 7.

 

Procedure 7(Separation of nickel ion from manganese and iron ion)

1. Add 3 mL of 6 M ammonia and stir well.

2. Separate the supernatant from any precipitate. Save the supernatant for Procedure 10 and Use the precipitate for Procedure 8.

 

Procedure 8(Confirmation of manganese ion)

1. Add 1 mL of 3% hydrogen peroxide solution to the precipitate from Procedure 7.

2. Stir, then heat the sample in the water bath until no more gas is generated.

3. Add 3 M H2SO4 by drops until the mixture is acidic.

4. Separate the supernatant from any precipitate and use it for Procedure 9.

 

Procedure 9(Confirmation of iron ions)

1. Add two drops of 0.2 M Potassium ferrocyanide to the solution from Procedure 8.

 

Procedure 10(Confirmation of nickel ion)

1. Add 1 drop of 6 M HCl. Then add 5 drops of dimethylglyoxime reagent to the solution from Procedure 7.

 

Equipment:

-Test tube (10), 10-mL

-Test tube rack

-Pipet, graduated, 10-mL

-Rubber bulb

-Pipet, plastic (7), 1-mL

-Centrifuge

-Beaker, 250-mL

-Evaporating dish

-Stirring rod

-Hot plate

-Litmus paper (10)

-pH paper (1 roll)

-6 M Sodium hydroxide (NaOH), 20-mL

-6 M Ammonia (NH3), 20 mL

-0.1 M Potassium chromate (k2CrO4), 20-mL

-1% Aluminon dye, 2 mL

-6 M Hydrochloric acid (HCl), 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, 20 mL

-Deionized water, 5 mL

-Marking pen