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I am attempting to isolate pure iodine from kelp using the method described here but I do not have any way of possibly obtaining cyclohexane. I was wondering if any easier to obtain solvents would work as well to isolate the iodine from the rest of the mixture. I was hoping to use a solvent that is easy to obtain in a grocery or hardware store.

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  • $\begingroup$ @ K_P Methylene chloride and chloroform are polar and both immiscible with water but actually have a very minimal solubilty . $\endgroup$
    – Technetium
    Sep 7, 2015 at 6:38

2 Answers 2

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Cyclohexane is used for this extraction because it is nonpolar, as is iodine. A more polar solvent like acetone or ethanol will also extract a whole bunch of other stuff like essential oils, proteins, and other polar compounds.

You want Mineral Spirits which you should be able to purchase at any quality hardware store or Walmart. Mineral spirits, mineral turpenine, or whatever you want to call it, is a mixture of saturated hydrocarbons distilled from petroleum. It is a general purpose paint thinner for oil-based paints. Since it is mainly C7-C12 alkanes, it will have a higher boiling point than cyclohexane $(140\ ^\circ\mathrm{C}$ vs $81\ ^\circ\mathrm{C})$., but it will have the same general polarity as cyclohexane.

If you can find products labeled as petroluem ether, light naphtha, or ligroin, all are alkane mixtures with lower boiling points than mineral spirits.

Another common low polarity paint thinner is toluene, which has a lower boiling point at $110\ ^\circ\mathrm{C}$.

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n-Pentane might work. It is very discriminating for nonpolar substances and its low BP, 36C, means it will be easily distilled from the iodine and recaptured. You would have to buy it from a chemical supply firm or online. Cyclohexane, BP 80C, is used because it will evaporate relatively easily and cleanly; slower evaporation rate could give larger iodine crystals. Mineral paint thinner is higher boiling and might be difficult to remove. Shop around, different brands could have different boiling ranges. Saturated hydrocarbons also have lower toxicity than aromatics like toluene or benzene, but inhalation and skin contact should be minimized and avoided. These solvents are all flammable.

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