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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 ...
Note that iodometry involves indirect titration of iodine liberated by reaction with the analyte, whereas iodimetry involves direct titration using iodine as the titrant. Redox titration using sodium thiosulphate, Na 2 S 2 O 3 (usually) as a reducing agent is known as iodometric titration since it is used specifically to titrate iodine. The ...
Sodium thiosulfate (sodium thiosulphate) is an inorganic compound with the formula Na 2 S 2 O 3 ·(H 2 O) x. Typically it is available as the white or colorless pentahydrate (x = 5), which is a white solid that dissolves well in water. The compound is a reducing agent and a ligand, and these properties underpin its applications. [2]
(B – S) is the difference between the volumes, in mL, of sodium thiosulfate required for the blank and for the sample, respectively; N is the normality of sodium thiosulfate solution in Eq/ L; 12.69 is the conversion factor from mEq sodium thiosulfate to grams of iodine (the molecular weight of iodine is 126.9 g/mol);
Sodium tetrathionate is formed by the oxidation of sodium thiosulfate (Na 2 S 2 O 3), e.g. by the action of iodine: [1] 2 Na 2 S 2 O 3 + I 2 → Na 2 S 4 O 6 + 2 NaI. The reaction is signaled by the decoloration of iodine. This reaction is the basis of iodometric titrations. Other methods include the coupling of sodium bisulfite with disulfur ...
Tetrathionate is a product of the oxidation of thiosulfate, S 2 O 2− 3, by iodine, I 2: 2 S 2 O 2− 3 + I 2 → S 4 O 2− 6 + 2I −. The use of bromine instead of iodine is dubious as excess bromine will oxidize the thiosulfate to sulfate.
Thiosulfate (IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur with the chemical formula S 2 O 2− 3. Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid , such as sodium thiosulfate Na 2 S 2 O 3 and ammonium thiosulfate (NH 4 ) 2 S 2 O 3 .
These salts are often generated by oxidation of thiosulfate. For example, tetrathionate is obtained by oxidation of thiosulfate ion with iodine (reaction is used in iodometry): S 2 O 2− 3 + I 2 → S 4 O 2− 6 + 2 I −. More specialized routes involve reactions of sulfur chlorides with bisulfite salts: SCl 2 + 2 HSO − 3 → [O 3 SSSO 3] 2 ...