To separate silicon dioxide (SiO2) and iron sulfide (FeS), you can use a technique called selective dissolution. Here's one way to achieve the separation:

Materials:

- Silicon dioxide (SiO2) and iron sulfide (FeS) mixture

- Sodium hydroxide (NaOH) solution

- Dilute hydrochloric acid (HCl) solution

- Filter paper

- Beakers

- Stirring rod

Procedure:

1. Dissolution in Sodium Hydroxide:

- Take a sample of the SiO2 and FeS mixture in a beaker.

- Add sodium hydroxide (NaOH) solution to the mixture.

- Stir the mixture to ensure complete contact between the NaOH solution and the solids.

2. Filtration:

- Filter the mixture using filter paper.

- This step separates the insoluble SiO2 from the soluble FeS.

- The SiO2 will remain on the filter paper, while the FeS will pass through as a solution.

3. Acidification of the FeS Solution:

- Collect the filtrate containing the FeS solution in a clean beaker.

- Add dilute hydrochloric acid (HCl) solution to the FeS solution dropwise while stirring.

- Acidification will cause the FeS to precipitate as a solid.

4. Second Filtration:

- Filter the acidified solution again using filter paper.

- This step separates the precipitated FeS from the remaining solution.

- The FeS will remain on the filter paper, while the impurities will be in the filtrate.

5. Washing and Drying:

- Wash both the SiO2 and FeS precipitates with distilled water to remove any residual impurities.

- Dry the precipitates separately in an oven or under a heat lamp.

By following these steps, you can separate silicon dioxide (SiO2) and iron sulfide (FeS) from their mixture through selective dissolution and filtration.