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A bottle of iodine solution used on apples to determine the correct harvest time. The chart shows the level of residual starch. The cut surface of an apple stained with iodine, indicating a starch level of 4–5. The iodine–starch test is a chemical reaction that is used to test for the presence of starch or for iodine. The combination of ...
The Minor test (also known as Minor's test, the starch–iodine test, and the iodine–starch test), described by Victor Minor in 1928, [1] is a qualitative medical test that is used to evaluate sudomotor function (perspiration or sweating). [2]
Dilute solutions containing iodine–starch complex. Using starch as an indicator can help create a sharper color change at the endpoint (dark blue to colorless). The color above can be seen just before the endpoint is reached. To a known volume of sample, an excess but known amount of I-is added, which the oxidizing agent then oxidizes to I 2.
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 ...
Starch is optionally added as an indicator to show the abrupt increase in iodide ion concentration as a sudden change from amber (free iodine) to dark blue (the "iodine-starch complex", which requires both iodine and iodide.) [7] Recently it has been shown, however, that the starch is not only an indicator for iodine in the reaction. [8]
A solution of triiodide (I 3 −) (formed by mixing iodine and potassium iodide) can be used to test for starch. The colorless solution turns dark blue in the presence of starch. [ 70 ] The strength of the resulting blue color depends on the amount of amylose present.
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The starch iodine test, a development of the iodine test, is based on colour change, as α-amylase degrades starch and is commonly used in many applications. A similar but industrially produced test is the Phadebas amylase test, which is used as a qualitative and quantitative test within many industries, such as detergents, various flour, grain ...