Iodine elemental

If the spent fuel is processed in a nuclear fuel reprocessing plant, the radioactive iodine species (elemental iodine and methyl iodide) trapped in the spent fuel elements ate ultimately released into dissolver off gases. The radioactive iodine may then be captured by chemisorption on molecular sieve 2eohtes containing silver (89). 

Although not abundant in quantity, iodine is distributed in rocks, soils, waters, plants, animal tissues, and foodstuffs (3,4). Excepting the possible occurrence of elemental iodine vapor in the air near certain iodine-rich springs, iodine never occurs free in nature. It is always found combined with other elements. 

The first iodine recovery from caUche occurred in 1852 the first iodine was exported to Europe in 1868, becoming the most important by-product of the nitrate production in terms of value. There are two ways for producing iodine from caUche iodates first, from solutions containing more equivalent iodine than its solubiUty as elemental iodine in the same solution of about 0.4 g/L at 25°C and second, from more diluted equivalent iodine solutions. 

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. 

In view of the chromophoric character of the elemental iodine itself, many colorimetric methods have been proposed for the deterrnination of inorganic iodine (88—92). These methods use the visible portion of the spectmm in reading iodine concentrations. In the visible range the extinction coefficient for iodine is not high enough to be used for minute quantities of iodine in water and other solvents (93). Higher sensitivities have been reported for elemental iodine in potassium iodide solutions in the ultraviolet (93,94). 

The synthesis of poly(arylene sulfide)s via the thermolysis of bis(4-iodophenyl) disulfide has been reported (78). The process leads to the formation of PPS and elemental iodine. This process presumably occurs analogously to that reported by Eastman Chemical Company. 

Japan was the lea ding producer of iodine in the 1980s, producing nearly 7000 metric tons per year. Elemental iodine was released into brine by treatment with sodium nitrate or chlorine. The free iodine was then adsorbed on activated carbon. It was stripped from the carbon with sodium hydroxide followed by acidification to form a slurry of elemental iodine ... 

Iodine. Iodine has been important for many years, primarily as an antiseptic (see Iodine and iodine compounds). In the American Civil War physicians used it to treat battie wounds. Elemental iodine is not very soluble in water, but dissolves readily when sodium iodide is added, forming triiodide + I I Iodine may thus be used as an aqueous solution but it has generally been used as a tincture of 2% iodine in 70% alcohol. Tests on... 

The data suggest that iodine will be released, predominantly, as cesium iodide under most postulated light water reactor accident conditions. However, formation of more volatile iodine species (e.g., elemental iodine and organic iodines) is not impossible under certain accident conditions. 

The assumed form of iodine is not substantially retained in early containment failure, but may be retained in the reactor coolant system, where cesium iodide is more strongly retained than the elemental iodine assumed by the RSS. 

Tire condensation method (Section II,A,1) applied for 1,2,4-thiadia-zolium salts and phenylsubstituted imidazoles leads to the thia-tetraazaful-valenes 91 and 92 (70TL481). Moreover, 2,4,5-tris(ethylsulfanyl)imida-zolium chloride was converted to the unsymmetrical heterofulvalene 93 by a self-condensation reaction in the presence of potassium carbonate and elemental iodine (85PS223) (Scheme 37). 

Treatment of this with elemental iodine affords the nuclearly substituted iodo derivative (87). Removal of the benzyl ether by reduction leads to iodothiouracil (88). ... 

Iodine occurs as iodide ions in brines and as an impurity in Chile saltpeter. It was once obtained from seaweed, which contains high concentrations accumulated from seawater 2000 kg of seaweed produce about 1 kg of iodine. The best modern source is the brine from oil wells the oil itself was produced by the decay of marine organisms that had accumulated the iodine while they were alive. Elemental iodine is produced by oxidation with chlorine ... 

Praseodymium tri-iodide, Prl3, as the starting material for reduction reactions, might be easily produced by the oxidation of praseodymium metal with elemental iodine [17]. With catalytic amounts of hydrogen dissolved in praseodymium metal powder, the reaction temperature can be as low as 230 °C [18]. Sublimation in high vacuum in tantalum tubes yields pure Prl3. 

The formation of triiodothyronine (T3) and tetra-iodothyronine (thyroxine T4) (see Figure 42—2) illustrates many of the principles of diversity discussed in this chapter. These hormones require a rare element (iodine) for bioactivity they are synthesized as part of a very large precursor molecule (thyroglobuhn) they are stored in an intracellular reservoir (colloid) and there is peripheral conversion of T4 to T3, which is a much more active hormone. 

When iodine and povidone are combined, a chemical reaction takes place forming a complex between the two entities. Some of the iodine becomes organically linked to povidone though the major portion of the complexed iodine is in the form of tri-iodide. Dilution of this iodophor results in a weakening of the iodine linkage to the carrier polymer with concomitant increases in elemental iodine in solution and antimicrobial activity. 

One Au-C bond in bis(thiazol-2-ylidene)gold cations is cleaved in the reaction with elemental iodine to give the corresponding (carbene)AuI complex and a 2-iodo-thiazolium salt, while chlorine and bromine oxidize the gold center to the gold(m) state.267... 

Reasonable yields (55-85%) of dialkylphosphinic acids have been reported from a complex reaction system beginning with red phosphorus, iodoalkane, and elemental iodine.26 Presumably, the phosphorus trihalide is generated as an intermediate. The reaction is worked up with a nitrous acid system from aqueous HCl/NaN02. 

IDAS A process for making isoprene (for the manufacture of a synthetic rubber) by the oxidative dehydrogenation of isopentene. Iodine is the initial reactant the hydrogen iodide produced in the reaction is reconverted to elemental iodine via nickel iodide. 

SAQ 8.9 Iodide reacts with thiosulphate to form elemental iodine. If the reaction solution contains a tiny amount of starch solution, then this I2 is seen by eye as a blue complex. The data below were obtained at 298 K. Determine the order of reaction, and hence its rate constant k. 

As indicated, only elemental iodine is found in the combustion products of organoiodine compounds [61,62,67]. The iodine formed in a static bomb is mostly in the crystalline state, but some is present in the aqueous and in the gaseous phases. The thermal corrections for dissolution and sublimation are very small and, therefore, static-bomb calorimeters may be used to study organoiodine compounds. However, to avoid the uncertainty in the final state due to the distribution... 

Elemental iodine can be formed from aqueous iodide ion (by means of the oxidative electrode reaction, 21 b -I- 2e ) by passing a charge of 8.04 x 10 C. The amount of iodine was subsequently determined (by titration with aqueous thiosulfate) to be 0.239 mol. What is the electrolytic efficiency ... 

A very successful example for the use of dendritic polymeric supports in asymmetric synthesis was recently described by Breinbauer and Jacobsen [76]. PA-MAM-dendrimers with [Co(salen)]complexes were used for the hydrolytic kinetic resolution (HKR) of terminal epoxides. For such asymmetric ring opening reactions catalyzed by [Co(salen)]complexes, the proposed mechanism involves cooperative, bimetallic catalysis. For the study of this hypothesis, PAMAM dendrimers of different generation [G1-G3] were derivatized with a covalent salen Hgand through an amide bond (Fig. 7.22). The separation was achieved by precipitation and SEC. The catalytically active [Co "(salen)]dendrimer was subsequently obtained by quantitative oxidation with elemental iodine (Fig. 7.22). 

Elemental iodine, I2, is a purphsh solid. Like solid carbon dioxide (dry ice), iodine sublimes. That is, it goes directly from the sohd to the gas phase without ever becoming liquid. So a bottle of iodine has a nice purple haze above the solid element. 

Let us now consider the formation of aryl iodides from aryl diazonium salts and potassium iodide in methanol (Singh and Kumar 1972a, 1972b). Electron-donor substituents decelerate the process as compared with benzene diazonium (the substituent is hydrogen), whereas electron acceptor substituents accelerate it. Oxygen inhibits the reaction, and photoirradiation speeds it up. As the authors pointed out, in the case of 4-nitrobenzene diazonium, the reaction leads not only to 4-iodonitrobenzene but also to nitrobenzene, elemental iodine, and formaldehyde. All of these facts support the following sequence of events ... 

Similar to the history of many other elements, iodine s discovery was serendipitous in the sense that no one was looking for it specifically. In 1811 Bernard Courtois (1777—1838), a French chemist, attempted to remove sodium and potassium compounds from the ash of burned seaweed in order to make gunpowder. After removing these chemicals from the ash, he added sulfuric acid (H SO j) to the remaining ash. However, he mistakenly added too much acid, which produced a violet-colored vapor cloud that erupted from the mixture. This violet vapor condensed on all the metallic objects in the room, leaving a layer of sohd black iodine crystals. Sir Humphry Davy (1778—1829) confirmed this discovery of a new element and named it iodine after the Greek word iodes, which means violet, but it was Courtois who was given credit for the discovery of iodine. 

Intramolecular cyclization of diphenylamines to carbazoles is one of the most versatile and practical methods. This has been achieved photochemically, thermally in the presence of elemental iodine at 350°C, or with platinum at 450-540°C, via free radicals with benzoyl peroxide in chloroform, or by using activated metals such as Raney nickel or palladium on charcoal. Most of these methods suffer from low to moderate yields, and, in some cases, harsh reaction conditions (8,480). 

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