CHEMISTRY OF +1 IODINE IN ALKALINE SOLUTION (thesis)

Chia, Yuan-tsan

doi:10.2172/4324768

Cited by 8 publications

(6 citation statements)

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“…These species may, however, play a role as intermediates during the establishment of equilibrium. Nevertheless, because of their very low concentrations (see Table 3) the equilibrium constants [3] assigned to their formation must be considered meaningless. The H2 0I'^ species, on the other hand, can, under carefully controlled conditions and low pH, be made to become a significant part of the system, but can also be ignored at pH > 5.…”

Section: Discussionmentioning

confidence: 99%

“…Despite the long history of the study of aqueous iodine solutions, no direct experimental evidence exists for the occurrence of iodine in the +1 oxidation State, which includes the postulated species Hj 01"^, HOI and 0I~ [1], Although a brief Polarographie investigation [2] has provided some evidence to substantiate the existence of HOI in aqueous Solution, and a peak in the visible absorption spectrum of an alkaline iodine Solution has been assigned to Ol" [3], the results are not conclusive. Nevertheless, iodine in the +1 State is assumed to play an important role in the partition of species at equilibrium and in the kinetics of oxidation and disproportionation of I2.…”

Section: Introductionmentioning

confidence: 99%

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The Equilibria and Kinetics of Iodine Hydrolysis

Palmer

Lietzke

1982

Radiochimica Acta

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lodine hydrolysis/Equilibriutn/Kinetics/Aqueous Solution SummaiyA complete set of equilibrium expressions involving all the relevant iodine speciesbelieved to result from hydrolysis and disproportionation was solved simultaneously as a function of initial iodine concentration, pH and temperature using the Newton-Raphson method. Conclusions could be drawn as to the relative iraportance of the major species and this model was validated by a limited number of experiments conducted at 25°C and II, ]" = 10"' gatom 1"'. The kinetics of I, disproportionation into the +1 and -1 oxidation states were combined with various rate expressions for the formation and disappearance of iodate and the entire system involving four differential equations was solved numerically as a function of initial iodine concentration and pH.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Equilibria and Kinetics of Iodine Hydrolysis

Palmer

Lietzke

1982

Radiochimica Acta

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“…-13 [17] , K2 = 2.3×10 -11 [18] K3 = 723 [19] , K4 = 22.2 [27] , K5 = 9, K6 = 0.1 [21] , and K7 = 1.3×10 13 [18] .…”

Section: Methodsmentioning

confidence: 99%

Iodine and Disinfection: Theoretical Study on Mode of Action, Efficiency, Stability, and Analytical Aspects in the Aqueous System

Gottardi

1999

Arch. Pharm. Pharm. Med. Chem.

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Although they have been in use for nearly 170 years, the mode of action of iodine‐based disinfectants is not yet clearly understood, as is manifested, for example, in diverging judgements about the relevance of the individual iodine species. Although studies based on calculated equilibrium concentrations in pure iodine solutions have already been done, there is a lack of knowledge about iodine solutions in the presence of additional iodide which would be of intrinsic importance for disinfection practice. Therefore, a re‐calculation was undertaken considering variations of this parameter in the pH range 0—14. The presented calculations concern fresh iodine solutions not affected by disproportionation (iodate formation) and provide information about the equilibrium concentrations of the species I‐, I2, I3‐, I5‐, I62, HOI, OI‐, HI2O‐, IO2‐, and H2OI+. Additional iodide and the pH value have a very pronounced influence on the individual equilibrium concentrations (several powers of ten); hence, conditions can be indicated where the number of species of virtual importance is drastically reduced. In the most common case with iodine in the presence of additional iodide at pH < 6, only I‐, I2, and I3‐ play a role. In the absence of additional iodide, at pH 8‐9 and at high dilution (c(I2) < 10‐5M), on the other hand, HOI accounts for over 90% of the oxidation capacity. At high iodide concentration (e.g. Lugol′s solution) the species I5‐ and I62‐ make up 8.2% of the oxidation capacity. The iodine cation H2OI+, frequently quoted as an active agent in disinfection, is without any relevance under the conditions occurring in practice, as are IO‐ and HI2O‐ which become important only at pH > 10. The stability problem (i.e. rate of iodate formation) arising at pH > 6 can be reduced to hypoiodous acid, as manifested in the simple rate law d[IO3‐]/dt = 0.25[HOI]3/[H+] which allows an estimation of stability under weakly alkaline conditions. The results of this study allow us to deduce general qualities of aqueous iodine solutions, such as reactivity, stability, and analytical aspects, and to estimate major disinfection‐orientated properties such as microbicidal activity, irritation, and incorporation effects. Though the calculations consider primarily preparations devoid of polymeric organic compounds capable of complexing iodine species, the results can be largely transferred to iodophoric preparations.

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“…Because it is so unstable to disproportionation ( K D = 8.5 × 10 14 M -1 ), − HOI must be generated in situ from some other reaction. There are many ways to generate HOI in solution, each with its respective advantages and disadvantages.…”

Section: Introductionmentioning

confidence: 99%

Disproportionation Kinetics of Hypoiodous Acid As Catalyzed and Suppressed by Acetic Acid−Acetate Buffer

1997

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The kinetics of the disproportionation of hypoiodous acid to give iodine and iodate ion (5HOI right harpoon over left harpoon 2I(2) + IO(3)(-) + H(+) + 2H(2)O) are investigated in aqueous acetic acid-sodium acetate buffer. The rate of iodine formation is followed photometrically at -log [H(+)] = 3.50, 4.00, 4.50, and 5.00, &mgr; = 0.50 M (NaClO(4)), and 25.0 degrees C. Both catalytic and inhibitory buffer effects are observed. The first process is proposed to be a disproportionation of iodine(I) to give HOIO and I(-); the iodide then reacts with HOI to give I(2). The reactive species (acetato-O)iodine(I), CH(3)CO(2)I, is postulated to increase the rate by assisting in the formation of I(2)O, a steady-state species that hydrolyzes to give HOIO and I(2). Inhibition is postulated to result from the formation of the stable ion bis(acetato-O)iodate(I), (CH(3)CO(2))(2)I(-), as buffer concentration is increased. This species is observed spectrophotometrically with a UV absorption shoulder (lambda = 266 nm; epsilon = 530 M(-)(1) cm(-)(1)). The second process is proposed to be a disproportionation of HOIO to give IO(3)(-) and I(2). Above 1 M total buffer, the reaction becomes reversible with less than 90% I(2) formation. Rate and equilibrium constants are resolved and reported for the proposed mechanism.

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CHEMISTRY OF +1 IODINE IN ALKALINE SOLUTION (thesis)

Cited by 8 publications

References 0 publications

The Equilibria and Kinetics of Iodine Hydrolysis

The Equilibria and Kinetics of Iodine Hydrolysis

Iodine and Disinfection: Theoretical Study on Mode of Action, Efficiency, Stability, and Analytical Aspects in the Aqueous System

Disproportionation Kinetics of Hypoiodous Acid As Catalyzed and Suppressed by Acetic Acid−Acetate Buffer

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