Iodine crystals can be separated from a mixture of sand using the process of sublimation. This technique involves heating the mixture to a temperature at which iodine vaporizes, leaving behind the sand. The vaporized iodine can then be collected and condensed back into crystals.

Here is a step-by-step procedure for separating iodine crystals from a mixture of sand using sublimation:

Materials:

- Mixture of iodine crystals and sand

- Glass beaker

- Heat source (such as a hot plate or Bunsen burner)

- Glass stirring rod

- Filter paper

- Funnel

- Glass jar or container

Procedure:

1. Prepare the mixture: Place the mixture of iodine crystals and sand in a glass beaker.

2. Heat the mixture: Place the beaker on a heat source and gently heat the mixture.

3. Stir the mixture: Use a glass stirring rod to stir the mixture continuously to ensure even heating.

4. Observe sublimation: As the temperature increases, the iodine crystals will begin to sublime, turning into a purple vapor.

5. Collect the iodine vapor: Place a filter paper on top of a funnel, and position the funnel over a glass jar or container. The purple iodine vapor will rise and pass through the filter paper, condensing into crystals inside the jar.

6. Continue heating: Continue heating the mixture until all the iodine crystals have sublimed and the sand remains in the beaker.

7. Cool and collect: Allow the glass jar or container to cool down. The iodine crystals will condense on the walls of the jar, forming crystals.

8. Scrape and store: Once the crystals are completely cool, carefully scrape them off the sides of the jar and collect them in a suitable container for storage.

By following this sublimation process, you can effectively separate iodine crystals from the sand mixture. The iodine crystals will be collected in a pure form, while the sand remains behind in the beaker.