Dissolved organic iodine

However, I2 and HOI are the likely intermediates formed by both abiotic and biotic processes during L oxidation. These intermediates, if formed, can be reduced back to I react with organic matter to form particulate or dissolved organic iodine (RI) compounds or be volatilized to the atmosphere as I2, HOI, or CH3I. Iodate can also react directly with humic material during reduction to form RI (58), but this reaction is more important in sedimentary environments and has not been documented in the photic zone. 

Iodine has had limited application for disinfection of swimming pools [7] and small public water supplies [8]. One application in a reverse osmosis system has also been reported by Turby and Watkins [9]. Advantages of iodine are greater stability than chlorine, lower residual requirement, and diminished chemical reactivity toward dissolved organic compounds. 

A specific description of a preferred practice of the invention with vanillin as the aromatic compound is as follows. Vanillin is dissolved in water with one molar equivalent of sodium hydroxide while the solution is warmed to 50°-100° C. One molar equivalent of iodine and two molar equivalents of sodium iodide are added to water to prepare one molar equivalent of NalS.Nal. This sodium triiodide solution is added to the sodium vanillate solution along with a catalytic amount of sulfuric acid--preferably from 5 to 10 mole %. The mixture is stirred about one hour at a temperature of 50°-100° C., then sodium hydroxide is added to make the solution alkaline (from 1 to 5N). The copper catalyst is then added and the mixture heated at reflux until the iodovanillin is consumed, about 12 hours. The excess hydroxide is then neutralized and the 5-hydroxyvanillin extracted with a water-immiscihle organic solvent. The aqueous phase bearing the sodium iodide is then subjected to oxidizing conditions and the resultant iodine precipitates from solution. The solid element is filtered out, and a sodium triiodide solution prepared by reducing a portion of the iodine to sodium iodide and dissolving the iodine in the iodide to make the sodium triiodide solution. 

In pore waters the dissolved T concentrations, which are higher than the total iodine concentration in seawater, can be observed with decomposition of particulate organic matter (e.g., Figure IB). In Figure IB the T pore-water concentrations are in micromolar units, compared to the total iodine concentration in seawater of <0.5 (jlM. Thus, the pore waters contain several times the amount of iodine that is found in seawater. Increased T concentrations and significant amounts of organic iodine are found in anoxic basins such as the Black Sea (29, 39, 40). 

DOI Dissolved (nonvolatile) organic iodine DO Dissolved oxygen... 

Figure 9.6 shows the vertical variation of dissolved (nonvolatile) organic iodine (DOI) at Sta. 17. DOI was obtained from the difference in T1 (total iodine = D + 107 + DOI) and from Huang ef a/., (2005). 

The coexistence of various inorganic and organic iodine species, in different proportions, has been reported in various environments (Liss et al., 1973 Couture and Seitz, 1983 Yuita, 1992, 1994 Yamada et al., 1999 Muramatsu and Ohmono, 1988 Baker et al., 2001). Organically bound iodine can be a significant fraction of total iodine in aqueous systems and in the atmosphere. For example, methyl iodide is an important gaseous form of iodine in the marine atmosphere and in releases from nuclear fuel reprocessing facilities, while dissolved organo-I compounds comprise up to 50% of total iodine in aqueous samples from estuaries, rivers, and rain (Santschi and Schwehr, 2004). 

Jubin, R.T. 1981. Organic iodine removal from simulated dissolver off-gas streams using silver-exchanged mordenite. Proceedings of the 16th DOE Nuclear Air and Cleaning Conference, San Diego, CA Oct. 20-23,1980, Ed. Melvin W. First. 

With regard to the formation of organoiodine compounds by homogeneous reaction in the liquid phase of the sump water, I2 (and potentially HOI) seems to be the most important iodine species. As was discussed in Section 7.3.3.4.2., the fractional concentration of I2 in the solution strongly depends, because of hydrolysis and disproportionation, on the sump water pH. The organoiodide production reactions are, therefore, primarily affected by the prevailing pH, but also by the available dissolved organic substances, the nature and concentration of which are... 

A method of estimating small amounts of water in organic liquids (and also in some inorganic salts) is that of Karl Fischer. The substance is titrated with a mixture of iodine, sulphur dioxide and pyridine dissolved in methyl alcohol. The essential reaction is ... 

Like bromine, iodine is soluble in organic solvents, for example chloroform, which can be used to extract it from an aqueous solution. The iodine imparts a characteristic purple colour to the organic layer this is used as a test for iodine (p. 349). NB Brown solutions are formed when iodine dissolves in ether, alcohol, and acetone. In chloroform and benzene a purple solution is formed, whilst a violet solution is produced in carbon disulphide and some hydrocarbons. These colours arise due to charge transfer (p. 60) to and from the iodine and the solvent organic molecules. 

To determine the exact peroxide content of benzoyl peroxide (and of other organic peroxides) the following procedure may be employed. Place about 0 05 g. of the sample of peroxide in a glass-stoppered conical flask add 5-10 ml. of acetic anhydride (A.R. or other pure grade) and 1 g. of powdered sodium iodide. Swirl the mixture to dissolve the sodium iodide and allow the solution to stand for 5-20 minutes. Add 50-75 ml. of water, shake the mixture vigorously for about 30 seconds, and titrate the liberated iodine with standard sodium thiosulphate solution using starch as indicator. 

Hydroiodic acid, the colorless solution formed when hydrogen iodide gas dissolves in water, is prepared by reaction of iodine with hydrogen sulfide or hydrazine or by an electrolytic method. Typically commercial hydroiodic acid contains 40—55% HI. Hydroiodic acid is used in the preparation of iodides and many organic iodo compounds. 

Tin does not react directly with nitrogen, hydrogen, carbon dioxide, or gaseous ammonia. Sulfur dioxide, when moist, attacks tin. Chlorine, bromine, and iodine readily react with tin with fluorine, the action is slow at room temperature. The halogen acids attack tin, particularly when hot and concentrated. Hot sulfuric acid dissolves tin, especially in the presence of oxidizers. Although cold nitric acid attacks tin only slowly, hot concentrated nitric acid converts it to an insoluble hydrated stannic oxide. Sulfurous, chlorosulfuric, and pyrosulfiiric acids react rapidly with tin. Phosphoric acid dissolves tin less readily than the other mineral acids. Organic acids such as lactic, citric, tartaric, and oxaUc attack tin slowly in the presence of air or oxidizing substances. 

Bromine is used as an analytical reagent to determine the amount of unsaturation in organic compounds because carbon—carbon double bonds add bromine quantitatively, and for phenols which add bromine in the ortho and para positions. Standard bromine is added in excess and the amount unreacted is deterrnined by an indirect iodine titration. Bromine is also used to oxidize several elements, such as T1(I) to T1(III). Excess bromine is removed by adding phenol. Bromine plus an acid, such as nitric and/or hydrochloric, provides an oxidizing acid mixture usefiil in dissolving metal or mineral samples prior to analysis for sulfur. 

A solid solution of starch in urea may also be employed. Reflux 1 g of soluble starch and 19 g of urea with xylene. At the boiling point of the organic solvent the urea melts with little decomposition, and the starch dissolves in the molten urea. Allow to cool, then remove the solid mass and powder it store the product in a stoppered bottle. A few milligrams of this solid added to an aqueous solution containing iodine then behaves like the usual starch indicator. 

Discussion. One of the most useful titrations involving iodine is that originally developed by Winkler18 to determine the amount of oxygen in samples of water. The dissolved oxygen content is not only important with respect to the species of aquatic life which can survive in the water, but is also a measure of its ability to oxidise organic impurities in the water (see also Section 10.103). Despite the advent of the oxygen-selective electrode (Section 16.36) direct titrations on water samples are still used extensively.19... 

When iodine dissolves in organic solvents, it produces solutions having a variety of colors. These colors arise from the different interactions between the I2 molecules and the solvent (Fig. 15.21). The element is only slightly soluble in water, unless I ions are present, in which case the soluble, brown triiodide ion, I,, is formed. Iodine itself has few direct uses but dissolved in alcohol, it is familiar as a mild oxidizing antiseptic. Because it is an essential trace element for living systems but scarce in inland areas, iodides are added to table salt (sold as iodized salt ) in order to prevent an iodine deficiency. 

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