Iodide ions iodate

The Landolt reaction (iodate + reductant) is prototypical of an autocatalytic clock reaction. During the induction period, the absence of the feedback species (Irere iodide ion, assumed to have virtually zero initial concentration and fomred from the reactant iodate only via very slow initiation steps) causes the reaction mixture to become kinetically frozen . There is reaction, but the intemiediate species evolve on concentration scales many orders of magnitude less than those of the reactant. The induction period depends on the initial concentrations of the major reactants in a maimer predicted by integrating the overall rate cubic autocatalytic rate law, given in section A3.14.1.1. 

Principle. An organic compound which contains chlorine is mixed with sodium peroxide and ignited in a closed metal bomb. The chlorine is thus converted to sodium chloride, and after acidification the chloride is estimated by the Volhard volumetric method. Bromine and iodine, when constituents of organic compounds similarly treated, are converted largely into sodium bromate and iodate respectively these ions are therefore subsequently reduced by hydrazine to bromide and iodide ions, and estimated as before. 

Iodide and iodate ions react under the influence of protons to yield iodine molecules which react with amylose to yield a blue clathrate complex ... 

Potassium iodate is a powerful oxidising agent, but the course of the reaction is governed by the conditions under which it is employed. The reaction between potassium iodate and reducing agents such as iodide ion or arsenic(III) oxide in solutions of moderate acidity (0.1-2.0M hydrochloric acid) stops at the stage when the iodate is reduced to iodine ... 

Discussion. Iodine (or tri-iodide ion Ij" = I2 +1-) is readily generated with 100 per cent efficiency by the oxidation of iodide ion at a platinum anode, and can be used for the coulometric titration of antimony (III). The optimum pH is between 7.5 and 8.5, and a complexing agent (e.g. tartrate ion) must be present to prevent hydrolysis and precipitation of the antimony. In solutions more alkaline than pH of about 8.5, disproportionation of iodine to iodide and iodate(I) (hypoiodite) occurs. The reversible character of the iodine-iodide complex renders equivalence point detection easy by both potentiometric and amperometric techniques for macro titrations, the usual visual detection of the end point with starch is possible. 

Sei f-Test 12.2B When iodide ions react with iodate ions in basic aqueous solution, triiodide ions, I,, are formed. Write the net ionic equation for the reaction. (Note that the same product is obtained in each half-reaction.)... 

Periodate and iodate ions may both be removed by reaction with iodide ion in acid solution this yields free iodine which can be removed by extraction209 or by centrifugation210-—or the iodine can be converted to iodide ion by titration with sodium thiosulfate.211 Periodate and iodate ions are also readily removed from solution by use of an anion-exchange resin.211a... 

The most widely used of the methods involving a reduction of periodate, only, to iodate employs the arsenite ion4 as reductant, in a solution maintained at neutrality with sodium bicarbonate, with iodide ion as catalyst. 

Matthews and Riley [99] preconcentrated iodide by co-precipitation with chloride ions. This is achieved by adding 0.23 g silver nitrate per 500 ml of seawater sample. Treatment of the precipitate with aqueous bromine and ultrasonic agitation promote recovery of iodide as iodate which is caused to react with excess iodide under acid conditions, yielding I3. This is determined either spectrophotometrically or by photometric titration with sodium thiosulfate. Photometric titration gave a recovery of 99.0 0.4% and a coefficient of variation of 0.4% compared with 98.5 0.6% and 0.8%, respectively, for the spectrophotometric procedure. 

Iodargyrite, natural occurrence of, 22 668 Iodates, 14 374-375 Iodate solutions, 14 362 Iodic acid, 14 375 Iodide analysis, of water, 26 41 Iodide ion, 14 367-368 25 488 Iodide-refining method, 26 149 for vanadium, 25 520 Iodides, 14 374 thorium, 24 763 tungsten, 25 379-380 uranium, 25 439... 

In order to remove effectively iodide by RNDS , oxidation of iodide to iodate or periodate is necessary. Iodide is oxidised to iodate with excess chlorine. Through contact of dechlorinated brine with the ion-exchange resin containing zirconium hydroxide, the iodide is therefore removed from the brine. 

The hypoiodite ion, however, is unstable, decomposing to iodate and iodide ions ... 

This procedure is more widely used in pharmacopoeial assays than the dye extraction procedure. Excess potassium iodide is added to an aqueous solution of the analyte, which is a lipophilic cation. A lipophilic ion pair is formed between the cation and the iodide ion and is then removed by extraction into an organic phase such as chloroform. The excess iodide remaining in the aqueous phase is then titrated in concentrated HCl (> 4 M) with potassium iodate. The iodate oxidises iodide to E, which immediately reacts with Cl to give ICl resulting in the following equation ... 

Ion pair formation with iodide followed by titration of excess iodide with iodate is utilised in pharmacopoeial assays of cetrimide, cetylpyridium bromide, domiphen bromide and benzalkonium chloride. 

Rebary B., Paul P. Ghosh P. K. Determination of iodide and iodate in edible salt by ion chromatography with integrated amperometric detection. Food Chemistry 2010 123(2) 529-534. 

In the hydrogen-oxygen and B-Z reactions considered above, the autocatalytic cycles correspond to a value for n of unity. The resulting rate law, rate = klab, involves the product of two concentrations and is known as quadratic autocatalysis . In the reaction between iodate and iodide ions, I is produced through an autocatalytic cycle which, at its simplest, corresponds... 

The reaction between iodate and arsenite ions appears to have contributions from both cubic and quadratic autocatalysis (the autocatalyst is the product, iodide ion). In the previous sections we have treated these two rate laws separately and by different methods. Both methods can be applied to the system in which these processes occur simultaneously, yielding results which, despite not being consistent at first sight, can be resolved by the idea of stability. 

Y. Xie, M. R. McDonald, and D. W. Margerum, Mechanism of the Reaction Between Iodate and Iodide Ions in Acid Solutions, Inorg. Chem. 1999, 38, 3938. 

In the case of a strong anion-exchange phase (SAX, which typically contains a quaternary amine), EOF reversal is observed, and an ion-exchange mechanism with negatively charged species will also result [69]. This approach has been successfully applied to the analysis of iodide and iodate [70], and has recently been reported for the... 

Iodate and iodide ions alone have no action on each other, but with hydrogen ions present a mutual oxidation and reduction of the iodine takes place. 

It was found impossible to measure the rate of decomposition by the evolution of gases because the release of these gas bubbles is very slow and erratic. The course of the reaction was followed by analyzing samples for the ammonium ion. Small amounts of the decomposing amalgam were forced through a capillary tube into a chilled solution of an iodate. The ammonium reacted with iodate ion to give iodide ion. The solution was then acidified with acetic acid and the iodine distilled out, collected and titrated with sodium thiosulfate. The method was checked with samples... 

Test for periodate (see note 1 below) This anion will give a positive test for oxidizing agents, but will not be detected in the systematic analysis. It will be necessary to remove first iodide or iodate by precipitation with silver nitrate in acid solution, and the excess silver ions with sodium chloride solution the resulting solution is strongly acidified with hydrochloric acid and an iron(II) salt is added. If a periodate is present, it will be reduced to iodine, which can be identified with carbon tetrachloride. 

The following procedure is used in the analysis of iodoso and iodoxy compounds. In a 200-cc. iodine flask are placed 100 cc. of water, 10 cc. of 6 N sulfuric acid, 2 g. of iodate-free potassium iodide, 10 cc. of chloroform, and finally the sample, about 0.25 g. The flask is shaken for fifteen minutes (or longer, if the reaction is not complete), and then the mixture is titrated with 0.1 N sodium thiosulfate. If the sample is pure the change of color in the chloroform layer may be taken as the end point, but if impurities are present starch must be used, for the impurities impart a brownish color to the chloroform. This solvent is desirable, as it facilitates the reaction with potassium iodide by dissolving the reaction products. Iodosobenzene may be differentiated from iodoxybenzene, for the former reduces iodide ion in a saturated sodium borate solution, whereas the latter does not.1 The reactions involved are ... 

In the present experiment the rate law for the reaction shown in Eq. (1) will be studied by the initial rate method, at 25°C and a pH of about 5. The initial concentrations of iodate ion, iodide ion, and hydrogen ion will be varied independently in separate experiments, and the time required for the consumption of a definite small amount of the iodate will be measmed. 

Lactones in acid-washed samples of modified cotton are not hydrolyzed in methylene blue solution. They may, however, be determined along with free carboxyl groups by steeping the material in a solution containing potassium iodide and iodate, sodium chloride, and an excess of sodium thiosulfate [427,428]. Hydrogen ions from the material liberate iodine according to the reaction... 

In Japan another process is used in which the iodine formed by chlorine oxidation is absorbed as polyiodide on an anionic ion exchanger. Desorption with alkali yields concentrated iodide- and iodate-containing solutions which are worked up to elemental iodine. 

The mechanism for the iodide-to-iodate conversion in seawater is still not well understood. This conversion is not a facile process. Here we compare iodide with other isoelectronic ions, including SH and its congeners Cl" (0.545 M in seawater) and Br (840 xM). The analysis indicates the conservative nature of Cl" under photochemical and thermal conditions. 

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