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)

- 6M Sodium hydroxide (NaOH), 20 mL

- 6 M Ammonia (NH3), 20mL

- 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 (K4[Fe(CN06]), 2 mL

- 3 M Sulfuric acid (H2SO4),  mL

- 3% Hydrogen peroxide (H2O2), 2 mL

- Unknown cation solution, 20 mL

- Deionized water, 5 mL

- Marking pen

 

Method:

Procedure 1: Detection of ammonium ion

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

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

3. Observe the litmus paper for a color change (red to blue). The color change will indicate the presence of ammonia

Procedure 2: Separation of silver and lead as chlorides

1. Use a clean pipet to transfer 2 mL of the known solution into a test tube

2. Add 2 to 3 drops of 6 M HCl. If a precipitate forms, keep adding 6 M HCl solution by drop until no more precipitate forms. If no precipitate formed, save this solution for Procedure 6.

3. Put the mixture in a centrifuge and add one drop of 6 M HCl

4. If no more precipitate forms, pour the supernatant into an additional test tube

5. If more precipitate does dorm, repeat steps three and four until no new precipitate forms

6. Label the sample and save the supernatant for Procedure 6 but use the precipitate in Procedure 3

Procedure 3: Separation of lead ion from silver ion

1. Using a clean pipet, add 3 to 4 mL of deionized water to the precipitate from Procedure 2

2. Heat the test tube by swirling it in the prepared hot water bath

3. Centrifuge the test tube to separate the supernatant from solids and save the supernatant for Procedure 5 but use the precipitate for Procedure 4

Procedure 4: Confirmation of silver ion

1. Add 10 drops of 6 M ammonia solution to the precipitate from Procedure 3 and stir it

2. Add 6 M HCl by drop until the precipitate forms again or until litmus paper indicates an acidic solution

Procedure 5: Confirmation of lead ion

1. Reheat the solution from Procedure 3 if it has any precipitation until the precipitate is dissolved entirely

2. Divide the sample into two test tubes and add several drops of 3 M H2SO4 to one of them

3. Add several drops of potassium chromate to the other test tube and stir

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

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

2. Ass 0.5 mL more of the NaOH and stir

3. Separate the supernatant from any precipitate. Save this supernatant for Procedure 11 but 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 to the precipitate from procedure 6 and stir well

2. Separate the supernatant from any precipitate and save the supernatant for Procedure 10 but 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 and stir and heat the sample in the prepared hot water bath until no more gas is created

2. Add 3 M H2SO4 drop by drop until the mixture become acidic

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

Procedure 9: Confirmation of iron ion

1. Add two drops of 0.2 M K[Fe(CN)6] to the solution from Procedure 8

Procedure 10: Confirmation of nickel ion

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

Procedure 11: Detection of aluminum ion

1. Neutralize the solution from Procedure 6 by adding 3 M H2SO4 drop by drop and use the pH paper to test the pH after each drop is added

2. Add 2 more drops of 3 M H2SO4 after the pH is neutral. Use the supernatant for Procedure 12

Procedure 12: Confirmation of aluminum ion

1. Add two drops of aluminon dye to the solution from Procedure 11

2. Add the 6 M ammonia drop by drop while stirring until the litmus paper detects a basic solution