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Methylene chloride (30 grams) is mixed with sodium iodide (120 grams) and warm acetone (100 ml) and heated in a sodawater bottle for ten hours; the bottle is then re-corked and the heating continued for a further ten hours. After standing overnight, the acetone solution is decanted from the sodium chloride, the latter washed with acetone, and the acetone distilled off ; water is then added and the crude methylene iodide extracted with ether. The ethereal solution contains iodine and is washed with water containing sodium hydrogen sulphite, dried, and the ether distilled off. The residue is then fractionated under reduced pressure, when, after a little methylene chloro-iodide has passed over, methylene iodide distils at about 150°C at 300 mmHg, the yield being at least 60%. If the recovered acetone, containing methylene chloride, is employed in a subsequent operation, the yield is about 10% higher.