Oxidants powerful

One of the most important applications of redox titrimetry is in evaluating the chlorination of public water supplies. In Method 9.3 an approach for determining the total chlorine residual was described in which the oxidizing power of chlorine is used to oxidize R to 13 . The amount of 13 formed is determined by a back titration with 8203 . 

In the DPD colorimetric method for the free chlorine residual, which is reported as parts per million of CI2, the oxidizing power of free chlorine converts the colorless amine N,N-diethyl-p-phenylenediamine to a colored dye that absorbs strongly over the wavelength range of 440-580 nm. Analysis of a set of calibration standards gave the following results... 

Analytical Methods. Most analytical methods use the oxidizing power of iodine for its deterrnination. The results are generaHy expressed as an equivalent concentration of elemental iodine. The choice of a method for the analysis of iodine depends on the concentration range to be deterrnined. 

Bromates are stable in storage. They have various uses based on their oxidizing power. Bromates can be formed by the disproportionation of bromine in basic solution ... 

Corrosion resistance of stainless steel is reduced in deaerated solutions. This behavior is opposite to the behavior of iron, low-alloy steel, and most nonferrous metals in oxygenated waters. Stainless steels exhibit very low corrosion rates in oxidizing media until the solution oxidizing power becomes great enough to breach the protective oxide locally. The solution pH alone does not control attack (see Chap. 4, Underdeposit Corrosion ). The presence of chloride and other strong depassivating chemicals deteriorates corrosion resistance. 

Nickel peroxide is a solid, insoluble oxidant prepared by reaction of nickel (II) salts with hypochlorite or ozone in aqueous alkaline solution. This reagent when used in nonpolar medium is similar to, but more reactive than, activated manganese dioxide in selectively oxidizing allylic or acetylenic alcohols. It also reacts rapidly with amines, phenols, hydrazones and sulfides so that selective oxidation of allylic alcohols in the presence of these functionalities may not be possible. In basic media the oxidizing power of nickel peroxide is increased and saturated primary alcohols can be oxidized directly to carboxylic acids. In the presence of ammonia at —20°, primary allylic alcohols give amides while at elevated temperatures nitriles are formed. At elevated temperatures efficient cleavage of a-glycols, a-ketols... 

The most important contnbution of this technology to the science of fluonne chemistry has been its ability to probe mechanistic aspects of elemental fluorine attack on organic molecules As has been long accepted fluorine attack on nonaromatic organic molecules is free radical in nature The great oxidizing power of fluonne and... 

This is due partly to the great insolubility of TI2O3 (2.5 X 10- "g r at 25 ) and partly to the enhanced oxidizing power of iodine in alkaline solution as a result of the formation of hypoiodate ... 

The oxidizing power of the halate ions in aqueous solution, as measured by their standard reduction potentials (p. 854), decreases in the sequence bromate > chlorate > iodate but the rates of reaction follow the sequence iodate > bromate > chlorate. In addition, both the thermodynamic oxidizing power and the rate of reaction depend markedly on the hydrogen-ion concentration of the solution, being substantially greater in acid than in alkaline conditions (p, 855). 

Aqueous perchloric acid solutions exhibit very little oxidizing power at room temperature, presumably because of kinetic activation barriers, though some strongly reducing species slowly react, e.g, Sn , Ti , V and V , and dithion-ite. Others do not, e.g. H2S, SO2, HNO2, HI and, surprisingly, Cr and Eu . Electropositive metals dissolve with liberation of H2 and oxides of less basic metals also yield perchlorates, e.g. with 12% acid ... 

These compounds, however, show no oxidizing power. Their diaziridine structure is thus erroneous. ... 

For the preparation of the parent substance, cyclic diazomethane (67), formaldehyde, chloramine, and ammonia were reacted. Diaziri-dine formation was successful in about 20% yield the diaziridine condensed with further formaldehyde to high molecular weight products the diaziridine detected by its oxidizing power was nonvolatile. Oxidation with dichromate in dilute sulfuric acid led to gaseous diazirine (67) [Eq. (56)]. It was only investigated in solution. 

Passivity is the loss of chemical reactivity of certain metals and alloys under specific environmental conditions. In other words, certain metals (e.g., iron, nickel, chromium, titanium, etc.) become relatively inert and act as noble metals (e.g., gold and platinum). Figure 4-420 shows the behavior of a metal immersed in an air-free acid solution with an oxidizing power corresponding to point A... 

Figure 4-420. Corrosion rate of a metal as a function of soiution oxidizing power (electrode potential). (From Ref [183].)...

Fig. 1.40 Schematic anodic polarisation curve for a passivatable metal (solid line), shown together with three alternative cathodic reactions (broken line). Open-circuit corrosion potentials are determined by the intersection between the anodic and cathodic reaction rates. Cathode a intersects the anodic curve in the active region and the metal corrodes. Cathode b intersects at three possible points for which the metal may actively corrode or passivate, but passivity could be unstable. Only cathode c provides stable passivity. The lines a, b and c respectively could represent different cathodic reactions of increasing oxidizing power, or they could represent the same oxidizing agent at increasing concentration.

Chlorinated water. The oxidizing power of chlorine-containing chemicals keeps swimming pool watar free of disease-causing microorganisms. 

Hydrogen peroxide tends to decompose in water, which explains why its solutions soon lose their oxidizing power. The reaction involved is disproportionation, combining the two halfreactions referred to above ... 

Halides, 562 Hall, Charles, 3,536 Halogen An element of Group 17,31 oxidizing power of 557 oxoacids of, 567t reactivity, 559 Head-to-head polymer, 613 Head-to-tail polymer, 613 Heat A form of energy that flows between two samples because of their difference in temperature, 197,214 Heat capacity The amount of heat required to raise the temperature one degree Celsius, 199... 

For example, the common use of sodium hypochlorite solution, NaOCl, as a bleaching solution depends upon the oxidizing action of hypochlorite, OC1-. Iodate ion, IO, also furnishes a strong oxidizing power, as shown by E° for the half-reaction I2-IO ... 

FIGURE 12.17 Iron nails stored in oxygen-free water (left) do not rust, because the oxidizing power of water itself is weak. When oxygen is present (as a result of air dissolving in the water, right), oxidation is thermodynamically spontaneous and rust soon forms. 

Self-Test 15.6B How does pH affect the oxidizing power of HCIO. ... 

Qualitatively, at least, there is a unifying theme and chemical correlation to be found in these series. Namely, values decrease with increasing reducing power of the ligands and/or increasing oxidizing power of the metal ions. These two statements can be joined to yield the simple result ... 

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