GB841456A - Electrolytic process for making periodic acid solutions - Google Patents

Abstract

841,456. Alkali per-iodates. ABBOTT LABORATORIES. Aug. 27, 1958 [Aug. 27, 1957], No. 27545/58. Class 41. Alkali per-iodates are prepared in an electrolytic cell having a porous diaphragm using as anolyte a solution of iodine in alkali containing also an alkali metal salt e.g. sulphate chloride or bbrate, in which is immersed a lead dioxide anode, whereby alkali iodate is formed; the electrolyte is then made acid and electrolysis continued whereby the iodate is converted to per-iodate. The alkali metal salt prevents the formation of insoluble alkali para-periodate on the anode. In a suitable apparatus, sublimed iodine is fed into a mixer 1 together with sodium hydroxide or carbonate, and sodium sulphate. A suitable mixture is 50 g. iodine, 20 g. NabH, and 10 g. sodium sulphate or borax, in 400 cc. water. The mixture is fed into the anolyte compartment 4 of an electrolytic cell provided with lead dioxide anode 5, graphite cathodes 6, 7 mounted in catholyte compartments bounded by porous diaphragms 8, 9, of alundum or asbestos. The catholyte solution is originally sodium hydroxide supplied from a tank 2, and diluted with water. Electrolysis is effected at 5‹ to 60‹C, and at a current density of 0À05 to 0À3 amp per sq. cm. of anode surface, and the anolyte is agitated. When the iodine is converted to iodate, the catholyte is removed and the diaphragms flushed with water, and then dilute sulphuric acid is admitted from a tank 11 and electrolysis continued, while sulphuric acid continues to flow through the diaphragm to the anolyte. After completion of this stage, the anolyte is passed through a filter 14 to remove any particles of lead dioxide, and the sodium meta-periodate recovered by crystallation, or the solution used directly e.g. for the oxidation of starch. U.S.A. Specifications 2,713,553 and 2,770,589 are referred to.