Preparation of Lyophobic Sol - Ferric Hydroxide Sol | Testbook.com

The goal of this experiment is to prepare ferric hydroxide sol.

Ferric hydroxide (Fe(OH) ₃ ) can form a lyophobic sol. Sulphides or metal hydroxides which are colloidal solutions , when treated with water, are termed as lyophobic colloids. Fe(OH) ₃ sol is obtained by hydrolysis of ferric chloride with boiling distilled water. The reaction is as follows:

The hydrochloric acid formed during the hydrolysis destabilizes the ferric hydroxide sol and therefore must be removed through the process of dialysis.

The following materials are needed for this experiment:

1. Glass rod
2. Round bottom flask
3. Boiling tube
4. 250 mL volume Conical flask
5. Tripod stand
6. Funnel
7. 250 mL volume Beaker
8. Burette
9. Wire gauze
10. Dropper
11. Burner
12. Wire gauze
13. Iron stand with clamp
14. Boiling tube
15. Distilled water
16. Ferric chloride solution

1. Clean a 250 mL volume conical flask with steam.

2. Refer to the figure below to understand how to steam clean the conical flask.

3. Prepare a 2% solution of ferric chloride by mixing 2 g of pure ferric chloride with 100mL of distilled water.

4. Take the steam-cleaned conical flask and add 100mL of distilled water.

5. Boil the water on a wire gauze.

6. Slowly add 10 mL of the ferric chloride solution using a dropper or burette.

7. Continuously stir the boiling water mixture while adding the ferric chloride solution.

8. Keep heating the mixture until it turns a brown or deep red color.

9. Let the mixture settle at room temperature.

10. Label the flask containing the mixture as ferric hydroxide sol.

• The presence of impurities can affect the Fe(OH) ₃ sol. Therefore, ensure to clean the conical flask by steaming.
• Add the FeCl ₃ solution drop by drop.
• Keep heating the mixture until it turns a deep red or brown color.
• Remove the formed hydrochloric acid (HCl) through dialysis to prevent the sol from destabilizing.

1. How do you prepare a 2% ferric chloride solution?

Ans: By dissolving 2 g of ferric chloride in 100 mL of distilled water.

2. Why is steaming out process necessary for cleaning the apparatus?

Ans: Because the presence of impurities can affect the ferric hydroxide sol. Hence, the apparatus is steam cleaned before the experiment.

3. Until what colour should the mixture of ferric chloride solution and distilled water be boiled?

Ans: Deep red or brown colour.

4. What is the result of the hydrolysis of ferric chloride?

Ans: It results in the formation of hydrochloric acid.

5. How much ferric chloride solution is added to 100 mL of boiling distilled water?

Ans: 10 mL.