Iodine solution

An alternative that has several advantages is Povidone-Iodine, PVP-I. This is more stable and less toxic than Lugol’s iodine. Used in the study of the iodination of propanone it gives good results with much lower concentrations of acid and propanone than Lugol’s iodine so minimises safety considerations. PVP-I is sold as a topical antiseptic for medical and veterinary applications.

Lugol’s iodine

To prepare 100cm³ of stock solution put 1g of potassium iodide and 1g of iodine into a mortar. Add a very small amount of water. Grind to a smooth mixture then add more water.

Make up to 100cm³ with water and store in a glass bottle.

Solutions of iodine lower than 1M are low hazard and do not need a warning label. The stock solution is less than 0.25M but eye protection and gloves should be worn while preparing it.