Iodide-iodate paper

To some extent the potassium iodide-iodate paper reveals the hydrogen ion concentration as well as the titration acidity. The reaction between iodide and iodate is described by the equation ... 

This is a time reaction and is very much influenced by the hydrogen ion concentration. The equation shows that H+ ions are removed from solution. Comparing the behavior of iodide-iodate paper in 0.0001 N HCl and in the acetic acid-acetate mixture, both reactions seem to be the same at first sight. The same brown or blue color appears. However, the paper treated with the buffer mixture gradually turns a deeper color because the hydrogen ions removed initially are replaced. This is not true of the hydrochloric acid. 

The I2O7 content of the periodates described is determined as follows The weighed sample is covered with 20 ml. of water, and 5 to 10 drops of 6N HC1 is added to hasten solution. No chlorine is liberated from the acid of this concentration. The solution is diluted to 100 ml., made just alkaline to phenolphthalein paper with borax, buffered with borax and boric acid (Muller and Wegelin Z. anal. Chem., 52, 755-759 (1913), and an excess of potassium iodide is added. Under these conditions, the periodate is reduced to iodate. The liberated iodine is titrated with 0.1N arsenite. 

Reactions of the three halide ions with iodate are reported as obeying different kinetic laws (Table 28). For the chloride and bromide reactions, the evidence is not extensive, and even the great attention given to the iodide reaction has not produced complete agreement about the reaction orders. Earlier papers refer to this last as the Dushman reaction, on account of a kinetic study which established the reaction as close to fifth order overall (rate = k[H ] [IOJ][I ] ). Kubina examined the same reaction in the presence of arsenite (which did not affect the rates) and claimed that the rate expression was different, viz. 

Davy says when M. Clement shewed iodine to me, he believed that the hydriodic acid was muriatic acid and M. Gay-Lussac, after his early experiments made originally with M. Clement, formed the same opinion, and maintained it when I first stated to him my belief that it was a new and peculiar acid, and that iodine was a substance analogous in its chemical relations to chlorine. In 1814-15 three papers on iodine by Davy were published by the Royal Society. The first, dated Paris, 10 December, 1813 , was read on 20 January 1814 the second, dated Florence, 23 March, 1814 , was read on 16 June and the third, dated Rome, 10 February, 1815 , was read on 20 April. The first contains an astonishing number of observations and describes many new compounds of iodine, including phosphonium iodide, iodine trichloride, and potassium iodate ... 

If iodide is present, it is best to conduct the test on filter paper (procedure (c)) in which the iodide is oxidized to iodate by hydrogen peroxide and any elementary bromine liberated is absorbed by filter paper. ... 

Paper-electrophoretic experiments have provided evidence for the formation of an unidentified species of iodine (7). With 1 M sodium hydroxide as a background electrolyte, in conjunction with Toyo Roshi No. 50 1 x 40 cm filter paper, a potential gradient of 200 volts/30 cm was applied for 1 hour to a drop of each solution of neutron-irradiated samples of ammonium iodide, potassium iodate and potassium periodate. The temperature of the migration cell was maintained at 10°. The migration velocities followed the sequence I">103>10. ... 

When neutron-irradiated telluric acid was dissolved in water and ammonium iodide, potassium iodate and potassium periodate added to the resulting solution of iodine activity the migration pattern corresponded to that already observed. However, when the same active solution was free of carrier iodine an unidentified fourth species was usually found at a position lying between iodate and iodide on the chromatographed paper. It was postulated that this species was iodite (lOg ). 

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