At present, there are three production processes of hydroiodic acid:
Direct method: using platinum asbestos as catalyst, iodine vapor (I2) reacts directly with hydrogen (H2) at 5℃ to obtain hydrogen iodide gas. Industrial production is mainly this method.
indirect method: PI3 is obtained by the reaction of red phosphorus (P) with iodine (I2), and the mixed aqueous solution of phosphorous acid (H3PO3) and hydroiodic acid (HI) is obtained by hydrolysis, and hydroiodic acid is obtained by distillation in the dark. This method is commonly used in the laboratory.
electrolysis: this is a new method introduced by American patent, which was developed by new york Electric Synthesis Company. The electrolyzer is divided into cathode zone, anode zone and middle zone by anion exchange membrane and cation exchange membrane, and the middle zone is between anion exchange membrane and cation exchange membrane. Iodine (I2) is reduced to iodine ion (I ()) at the cathode, oxidized to generate hydrogen ion (H ()) at the anode, and then I (and H (recombine into hydroiodic acid in the middle region.
the technical requirements of the direct method are very high, which is why only the United States can produce hydroiodic acid industrially. The ion exchange membrane used in electrolysis is very expensive and monopolized by DuPont, so the equipment investment is very large.
preparation of hydroiodic acid from red phosphorus: iodine and red phosphorus or yellow phosphorus are put into water for reaction, after the reaction, they are filtered and distilled, and the fractions at 125 ~ i3℃ are collected to obtain hydroiodic acid.
use: used as analytical reagent, and also used for preparation of iodide.