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Toxic by all routes of exposure. Highly lung-irritant vapour evolved from the solid and from concentrated solutions. Use in a fume cupboard if practicable, otherwise use small quantities in a well-ventilated area. Use eye and skin protection when splashes are possible. Do not mix with concentrated ammonia solution, since a highly explosive nitrogen triiodide complex is formed. Do not mix with acetaldehyde, or antimony metal since violently exothermic reactions may occur. The preparation of alkyl iodides from iodine is not recommended due to the carcinogenic properties of the alkyl iodides. Reaction of iodine with aluminium powder, catalysed by a drop of water, is safe if carried out in a fume cupboard or in the open. The induction period can be reduced if a dilute aqueous detergent solution is used. If heating more than 0.5 g of iodine strongly, do so only in a fume cupboard since the vapour is a powerful lung irritant.
Smaller portions may be heated gently in a test tube at 45C with a Bunsen flame to demonstrate sublimation and condensation. The test tube should be stoppered to minimise escape of iodine. Typically, student use of solid should be limited to 0.2 g (2 rice grains) per activity per group/person. Iodine solution stains starch granules blue, proteins brown, nuclei dark brown, chloroplasts brown (black if starch is present), cellulose walls yellow, and lignified walls deep yellow. Store iodine container inside another container, since the lid often deteriorates.
Iodine solution, is made by dissolving solid iodine in potassium iodide solution.
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See Appendix F.
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