Iodine value
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2008-03-23T02:35:11Z
Smaines
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The '''iodine value''' (or "iodine adsorption value" or "iodine number") in [[chemistry]] is the mass of [[iodine]] in grams that is consumed by 100 grams of a [[chemical substance]]. An iodine solution is yellow/brown in color and any chemical group in the substance that reacts with iodine will make the color disappear at a precise concentration. The amount of iodine solution thus required to keep the solution yellow/brown is a measure of the amount of iodine sensitive reactive groups.
One application of the iodine number is the determination of [[saturated compound|saturation]] of [[fatty acid]]s as double bonds in fatty acids also react with iodine compounds. The higher the iodine number, the more [[unsaturated fatty acid]] bonds are present in a fat. [http://domanski.cs.csi.cuny.edu/klibaner/LIPID.htm] In a typical procedure the acid is treated with an excess of the '''Hanus solution''' which is a solution of '''iodobromine''' (BrI). Unreacted iodobromine is reacted with [[potassium iodide]] which converts it to iodine. The iodine concentration is then determined by titration with [[sodium thiosulfate]].
Standard methods for analysis are for example [[ASTM]] D5768-02(2006) and [[DIN]] 53241.
For a simple analysis, 0.2 grams of the fat is mixed with 20cm<sup>3</sup> Wij's solution and 10cm<sup>3</sup> [[1,1,1-trichloroethane]]. It is then left in the dark for 30mins. Next, 15cm<sup>3</sup> of 10% [[potassium iodide]] solution and 10cm<sup>3</sup> of deionised water is added. This is then titrated against 0.1M [[sodium thiosulfate]] (VI) solution.
1cm<sup>3</sup> of 0.1M sodium thiosulphate solution = 0.01269g of [[iodine]]. The difference between a control titration and the titration with the fat present multiplied by this factor gives the mass of iodine absorbed by the oil.
== See also ==
* [[Saponification value]]
* [[Acid number]]
* [[Bromine number]]
[[Category:Analytical chemistry]]
[[Category:Iodine|Number]]
[[ar:عدد اليود]]
[[de:Iodzahl]]
[[es:Índice de yodo]]
[[it:Numero di iodio]]
[[lv:Jodskaitlis]]
[[ja:ヨウ素価]]
[[pl:Liczba jodowa]]
[[ru:Иодное число]]
[[fi:Jodiluku]]