Experimental Procedure If not already prepared, the iodine reagent is prepared by dissolving 25 g of iodine in a solution of 50 g of potassium iodide in 200 mL of water. The potassium iodide is added to increase the solubility of iodine in water, owing to the formation of potassium triiodide, KI3, by the reaction: I2 + KI → KI3. If the substance is water-soluble, dissolve 2 to 3 drops of a liquid or an estimated 50 mg of a solid in 2 mL of water in a small test tube, add 2 mL of 3 M sodium hydroxide, and then slowly add 3 mL of iodine solution. In a positive test the brown color disappears, and yellow iodoform separates. If the substance tested is insoluble in water, dissolve it in 2 mL of dioxane, proceed as above, and at the end dilute with 10 mL of water. Iodoform can be recognized by its odor and yellow color and, more definitely, by its melting point, 119°C. The substance can be isolated by vacuum filtration of the test mixture or by adding 2 mL of chloroform, shaking the stoppered test tube to extract the iodoform into the small lower layer, withdrawing the clear part of this layer with a capillary dropping tube, and evaporating it in a small tube on the steam bath. The crude solid is recrystallized from methanol-water.

Experimental Procedure If not already prepared, the iodine reagent is prepared by dissolving 25 g of iodine in a solution of 50 g of potassium iodide in 200 mL of water. The potassium iodide is added to increase the solubility of iodine in water, owing to the formation of potassium triiodide, KI3, by the reaction: I2 + KI → KI3. If the substance is water-soluble, dissolve 2 to 3 drops of a liquid or an estimated 50 mg of a solid in 2 mL of water in a small test tube, add 2 mL of 3 M sodium hydroxide, and then slowly add 3 mL of iodine solution. In a positive test the brown color disappears, and yellow iodoform separates. If the substance tested is insoluble in water, dissolve it in 2 mL of dioxane, proceed as above, and at the end dilute with 10 mL of water. Iodoform can be recognized by its odor and yellow color and, more definitely, by its melting point, 119°C. The substance can be isolated by vacuum filtration of the test mixture or by adding 2 mL of chloroform, shaking the stoppered test tube to extract the iodoform into the small lower layer, withdrawing the clear part of this layer with a capillary dropping tube, and evaporating it in a small tube on the steam bath. The crude solid is recrystallized from methanol-water.