Iodine in organic combination

It is thought that iodine in organic combination is less well absorbed than the inorganic form. Plants contain a higher proportion of inorganic iodide than do foods of animal origin. 

Many methods of determination have been published for the decomposition of compounds containing iodine in organic combination, their numbers suggesting that difficulties may be encountered in obtaining satisfactory results. They include ... 

A rapid method for the determination of iodine in organic combination has been described by Zak and Boyle. This method uses chloric acid as... 

A general method for the estimation of antimony, either in organic combination or as an inorganic salt, is the bromate titration method. It is preferable to the method of titration with iodine in the presence of bicarbonate unless the material being estimated is a fairly pure salt, since the solution being titrated may be coloured somewhat and there is often difficulty in the use of starch as indicator. The bromate method is applicable in the presence of arsenic. 

Iodine occurs to a minute extent (less than 0.001 %) in sea water, but is found in greater concentration, combined in organic form, in certain seaweeds, in oysters and in cod livers. Crude Chile saltpetre, or caliche contains small amounts of sodium iodate, NalOj. from which iodine can be obtained (see below). Some insoluble iodides, for example liiose of silver and mercury(II), occur in Mexico. Iodine is found in the human body in the compound thyroxin in the thyroid gland deficiency of iodine in diet causes enlargement of this gland (goitre). 

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. 

Analysis of Fats.—The iodine value of a fat or oil is a quantitative measure of the number of carbon-carbon double bonds which it contains. This number is the amount of iodine in grammes which combines chemically with 100 g. of the fat or oil. Nowadays the number of double bonds in organic compounds is usually determined with per-benzoic acid (cf. p. 111). 

On Dec. 20th, 1813, J. L. Gay Lussac18 read a further memoir on the combinations of the new element with oxygen on March 21st, 1814, J. J. Colin and H. G. deClaubry communicated observations made in J. L. Gay Lussac s laboratory on the action of iodine on organic compounds by June 4th, 1814, L. N. Vauquelin had studied the action of iodine on ammonia, iron, mercury, and alcohol and finally, on Aug. 1st, 1814, J. L. Gay Lussac communicated his famous Memoire sur ViodeM In this... 

If the solution is titrated with standard sodium thiosulphate solution, the total concentration of the iodine, both as free I2 and combined as IJ, is obtained, since, as soon as some iodine is removed by interaction with the thiosulphate, a fresh amount of iodine is liberated from the tri-iodide in order to maintain the equilibrium. If, however, the solution is shaken with carbon tetrachloride, in which iodine alone is appreciably soluble, then the iodine in the organic layer is in equilibrium with the free iodine in the aqueous solution. By determining the concentration of the iodine in the carbon tetrachloride solution, the concentration of the free iodine in the aqueous solution can be calculated from the known distribution coefficient, and therefrom the total concentration of the free iodine present at equilibrium. Subtracting this from the total iodine, the concentration of the combined iodine (as Ij) is obtained by subtracting the latter value from the initial concentration of potassium iodine the concentration of the free KI is deduced. The equilibrium constant ... 

Cleaning Up Combine all reaction mixtures in a beaker, add a few drops of acetone to destroy any unreacted iodine in potassium iodide reagent, remove the iodoform by suction filtration, and place it in the halogenated organic waste container. The filtrate can be flushed down the drain after neutralization (if necessary). 

Retention is a term widely used in the literature to denote either qualitatively, the appearance of radioactive atoms in a particular molecular species, or quantitatively, the percentage of the radioactive atoms in such a species, or loosely, the sum total of all such combinations. Thus one speaks of retention of iodine as ethyl iodide or organic retention of iodine in irradiated ethyl iodide. The latter means the sum of all the organic species containing iodine such as ethyl and methyl iodide, methylene iodide, etc. 

It is not yet a well established concept in organic chemistry, but it appears that there is a principle of maximum hardness,235 which says that reactions take place in the direction that increases hardness. We can use the two reactions in Fig. 3.1 to see how this works. The hardness of a pair of starting materials is measured by taking the smaller value of I and the more positive value of A, and using Equation 3.3. The combination of a methyl radical and a fluorine atom has a change from rj = 9.82 — 3.40 = 6.42 to rj = 18.7, whereas the combination of a methyl radical with an iodine atom has a change from rj = 9.82 — 3.06 = 6.76 to rj = 9.30. Thus the former is the reaction with the greater increase in hardness, with methyl fluoride a very hard molecule, and is the more exothermic reaction. 

A method for the determination of iodide, iodate, organic iodine, and total iodine in seawater was developed by radiochemical NAA combined with ion-exchange preseparation (Hou et ai, 1999). The filtered seawater was passed through an anion-exchange column. The column was washed with deionized water, and the effiuent and washings were collected for the determination of the sum of iodate and organic iodine. The column was washed with... 

It is known that iodide or iodate have a high bioavailability (>95%) in humans and animals. However, iodine in the diet may combine with different components and exist as organic iodine, which may have a low uptake in the digestive tract. During the last decade the iodine supply in many countries has increased significantly, but there is still a high frequency of goiter. This may be related to the iodine bioavailability in foodstuffs (Hurrell, 1997). 

Only the covalent Ij molecules will dissolve in an organic solvent. If an aqueous solution of iodine in iodide ions is shahen with an orpnic solvent, the concentration of iodine in the solvent can be measured and divided by the partition coeffkieni to give the concentration of iodine molecules in the aqueous layer. The concentrscion of iodine combined as I, ions is obtained by subtracting the free iodine from the total iodine concentration. The concentration of I ions b obtained by subtracting (l) from the original concentration of I ... 

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