Dialysis of lyophilic and lyophobic sol

In this article, we have discussed the procedure to perform an experiment to purify lyophilic and lyophobic sol by the method of dialysis. By reading the content on this page you will be able to understand the steps to conduct the experiment. Try the experiment and compare your result with this.

Aim:

The aim of this experiment – to purify lyophilic and lyophobic sol by dialysis.

Theory:

The purification of lyophilic and lyophobic sols is carried out through a process called dialysis where the colloidal particles cannot pass through a parchment or cellophane membrane but the ions of an electrolyte can.

Materials required:

The apparatus and materials required for this experiment are as follows:

  1. Beaker of volume 400 mL
  2. Parchment/cellophane membrane
  3. Test tubes
  4. Funnel with long stem
  5. Iron stand
  6. Dropper
  7. Starch sol mixed with iodine solution, silver nitrate, and sodium chloride

Experimental setup:

Purification of colloid

Procedure:

  1. Take a square parchment/ cellophane paper whose size is 30 cm × 30 cm
  2. Dip the sheet in water and make it into a conical shape
  3. Add egg albumin colloidal dispersion in the cellophane/parchment paper cone
  4. Make use of a thread to tie the cone and hang it in a channel filled with distilled water
  5. After 30 minutes, check the channel water for the presence of ions.
  6. For every 30 minutes keep changing the water from the channel till it separates Na+ and Cl ions.
  7. You can determine the presence of Na+ and Cl ions by the simple test:
  8. Take two test tubes
  9. Add channel water in both the tubes.
  10. Add uranyl zinc acetate in one test tube and silver nitrate solution in the other tube.
  11. If a yellow precipitate with uranyl zinc acetate is formed then it means sodium ions are still present.
  12. If a white precipitate with silver nitrate is formed then it means Cl ions are still present.
  13. Make a note of the time required to purify colloidal dispersion.

Precautions to be taken during the experiment:

  • During the process of dialysis create airtight parchment bag to ensure that water does not get inside the bag.
  • Remember to keep the neck of the parchment bag just above the water surface.
  • For every 30 minutes change the water from channels during the process of dialysis.

Viva Voce:

1. What is the size of the cellophane sheet used in the experiment?

Ans: A square sheet of size 30 cm × 30 cm.

2. What is the role of uranyl zinc acetate solution?

Ans: It helps to detect the presence of Na+ ions in the channel water.

3. What is the role of silver nitrate solution?

Ans: It helps to detect the presence of Cl ions in the channel water.

4. How do you determine the presence of Na+ ions?

Ans: When uranyl zinc acetate solution is added the channel water forms a yellow precipitate.

5. How do you determine the presence of Cl ions?

Ans: When uranyl zinc acetate solution is added the channel water forms a white precipitate.

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