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Iodometry, known as iodometric titration, is a method of volumetric chemical analysis, a redox titration where the appearance or disappearance of elementary iodine indicates the end point. Note that iodometry involves indirect titration of iodine liberated by reaction with the analyte, whereas iodimetry involves direct titration using iodine as ...
The amount of dissolved oxygen is directly proportional to the titration of iodine with a thiosulfate solution. [1] Today, the method is effectively used as its colorimetric modification, where the trivalent manganese produced on acidifying the brown suspension is directly reacted with ethylenediaminetetraacetic acid to give a pink color. [ 2 ]
Close to the endpoint, the starch is added, and the titration process is resumed taking into account the amount of thiosulfate added before adding the starch. The color change can be used to detect moisture or perspiration, as in the Minor test or starch–iodine test. A starch agar plate filled up with iodine. A holo is present around B. subtilis.
Sodium thiosulfate is used to reduce iodine back to iodide before the iodine can complex with the starch to form the characteristic blue-black color. Iodine is generated: 2 I − + S 2 O 2− 8 → I 2 + 2 SO 2− 4. And is then removed: I 2 + 2 S 2 O 2− 3 → 2 I − + S 4 O 2− 6. Once all the thiosulfate is consumed the iodine may form a ...
The basic principle of iodine value was originally introduced in 1884 by A. V. Hübl as “Jodzahl”. He used iodine alcoholic solution in presence of mercuric chloride (HgCl 2) and carbon tetrachloride (CCl 4) as fat solubilizer. The residual iodine is titrated against sodium thiosulfate solution with starch used as endpoint indicator. [4]
A common example of a redox titration is the treatment of a solution of iodine with a reducing agent to produce iodide using a starch indicator to help detect the endpoint. Iodine (I 2) can be reduced to iodide (I −) by, say, thiosulfate (S 2 O 2− 3), and when all the iodine is consumed, the blue colour disappears. This is called an ...
The iodine is released in proportion to the oxygen in the sample, thus the oxygen concentration is determined with a redox titration of iodine with thiosulfate using a starch indicator. [49] Vitamin C: Also known as ascorbic acid, vitamin C is a powerful reducing agent.
To measure the iodine, a redox titration is performed using sodium thiosulfate. 2 S 2 O 2− 3 + I 2 → S 4 O 2− 6 + 2 I −. The acidic conditions (excess acetic acid) prevents formation of hypoiodite (analogous to hypochlorite), which would interfere with the reaction.