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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 starch and iodine is intensely blue-black. [1] [2] The interaction between starch and the triiodide anion (I − 3) is the basis ...
The iodometric titration is a general method to determine the concentration of an oxidising agent in solution. In an iodometric titration, a starch solution is used as an indicator since it can absorb the I 2 that is released, visually indicating a positive iodine-starch test with a deep blue hue. This absorption will cause the solution to ...
The iodine clock reaction is a classical chemical clock demonstration experiment to display chemical kinetics in action; it was discovered by Hans Heinrich Landolt in 1886. [1] The iodine clock reaction exists in several variations, which each involve iodine species (iodide ion, free iodine, or iodate ion) and redox reagents in the presence of ...
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]
Rice starch as surface treatment of paper has been used in paper production in China since 700 CE. [10] In the mid eighth century production of paper that was sized with wheat starch started in the Arabic world. [11] Laundry starch was first described in England in the beginning of the 15th century and was essential to make 16th century ruffed ...
The acidic conditions (excess acetic acid) prevents formation of hypoiodite (analogous to hypochlorite), which would interfere with the reaction. A starch indicator solution is used, for which amylose forms a blue to black solution with iodine and is colourless when the iodine is converted to iodide titrated.
The chemical reaction associated with this method of analysis involves formation of the ... sodium thiosulfate solution with starch used as endpoint indicator. [4]
As an alternative, ascorbic acid can be treated with iodine in excess, followed by back titration with sodium thiosulfate using starch as an indicator. [40] This iodometric method has been revised to exploit the reaction of ascorbic acid with iodate and iodide in acid solution. Electrolyzing the potassium iodide solution produces iodine, which ...