A mixture of 22 g. (0.1 mole) of iodosobenzene (p. 483), 24 g. (0.1 mole) of iodoxybenzene (p. 485), and 200 ml. of 1 N sodium hydroxide (Note 1) is gently stirred for 24 hours. The resulting brown slurry is thoroughly stirred with 1 l. of cold water, and, after the mixture settles, the supernatant solution of diphenyliodonium iodate is decanted through a filter. The solid residue is extracted twice with 500-ml. portions of water, and the extracts are separated, by decantation through a filter, from the small amount of tarry residue. An aqueous solution of 20 g. (0.12 mole) of potassium iodide is added to the combined filtrates. After the bulky white precipitate of diphenyliodonium iodide has stood for an hour or two, with occasional shaking, it is filtered with suction, washed with water, and dried on porous tile at room temperature. The product weighs 29–30 g. (70–72%) and melts at 172–175° with vigorous decomposition.