Exercise 41. Hydrogen Iodate

Alternate Method.—Have at hand 300 to 400 cc. of hydrogen peroxide solution (3 per cent). In a 750-cc. flask, place 10 g. of very finely powdered iodine, 10 cc. of concentrated nitric acid, and 50 cc. of hydrogen peroxide solution and loosely stopper the flask with a glass stopper or a small funnel to minimize loss of iodine. Heat the mixture on the water bath to about 70°. Shake the flask from time to time when the solution fails to show a deep color due to dissolved iodine. Observe when the reaction starts, as shown by the first decrease in color. Whenever the solution again becomes deeply colored, add more hydrogen peroxide. Continue the process until the iodine is all oxidized and then rapidly evaporate the solution to a small volume. 

To remove the nitric acid and the organic matter introduced with the peroxide (added as a negative catalyst), evaporate the solution to dryness in a small porcelain dish. Heat the residue in an air oven for at least 2 hr., first at 140 to 150° and later at 170 to 180°. Extract the iodic acid with boiling water and filter off and reject the dark-colored residue. Evaporate the solution to dryness and partially dehydrate the solid by heating it in an air oven at 150 to 200°, avoiding overheating. 

Dissolve nearly all of the partially dehydrated solid in the minimum amount of hot water, filter, cool the filtrate, and place the clear solution in a crystallizing dish in a desiccator over anhydrous calcium chloride. If necessary, seed with a crystal of iodic acid. When but a very little mother liquor remains, reject this and wash the crystals with a few drops of cold water, drying them on paper. 

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