To obtain a sample of pure iodine from a mixture of iodine and lead sulfate (PbSO₄), you can use a separation technique based on the solubility differences between the two substances. Here’s a stepwise method:
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Dissolve lead sulfate: Begin by adding water to the mixture. Lead sulfate is not very soluble in water, so it will remain as a solid precipitate while iodine, being a non-polar molecule, will not dissolve significantly in water either.
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Filtration: Use a filter paper and a funnel to filter the mixture. The lead sulfate will remain on the filter paper as a residue while any iodine present will usually stay on the filter due to its insolubility in water. However, if you have any dissolved iodine in a polar solvent or in its vapor phase, you may consider the next step.
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Sublimation (if necessary): If any of the iodine is carried through with the water or if you have sublimed iodine in a vapor form, you can heat the filtered residue gently. Iodine can sublime when heated, changing from solid to gas and then back to a solid upon cooling. This process can concentrate the iodine into a pure form.
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Collection of iodine: After sublimation, place a cold surface (like a glass petri dish) above the heating source so that as iodine vapor rises, it will condense on this cold surface. Once cooled, you can scrape off the condensed iodine to collect it.
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Final purification: If there are still impurities, you can repeat the sublimation process to ensure the iodine is pure.
By using the filtration and sublimation processes, you can effectively separate and purify iodine from a mixture containing lead sulfate. Always remember to conduct such experiments in a well-ventilated area and with appropriate safety precautions, given the potential hazards associated with iodine fumes and lead compounds.
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