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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 ...
When the solutions are mixed, the second reaction causes the iodine to be consumed much faster than it is generated, and only a small amount of iodine is present in the dynamic equilibrium. Once the thiosulfate ion has been exhausted, this reaction stops and the blue colour caused by the iodine – starch complex appears.
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).
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 ...
For example, a drop of iodine on a slightly rotten part (not the skin) of an apple will stay yellow or orange, since starch is no longer present. If the iodine is applied and takes 2–3 seconds to turn dark blue or black, then the process of ripening has begun but is not yet complete. If the iodine becomes black immediately, then most of the ...
Some cases of reaction to povidone-iodine (Betadine) have been documented to be a chemical burn. [83] Medical use of iodine compounds (i.e. as a contrast agent) can cause anaphylactic shock in highly sensitive patients, presumably due to sensitivity to the chemical carrier. Cases of sensitivity to iodine compounds should not be formally ...
In an iodine clock reaction, colour changes after a time delay.. A chemical clock (or clock reaction) is a complex mixture of reacting chemical compounds in which the onset of an observable property (discoloration or coloration) occurs after a predictable induction time due to the presence of clock species at a detectable amount. [1]
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]