Search results
Results from the WOW.Com Content Network
To this a solution containing potassium iodide, sodium thiosulfate, and starch is added. There are two reactions occurring simultaneously in the solution. In the first, slow reaction, iodine is produced: H 2 O 2 + 2 I − + 2 H + → I 2 + 2 H 2 O. In the second, fast reaction, iodine is reconverted to two iodide ions by the thiosulfate:
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 first reaction of iodine with SO 2 and water is as follows: . SO 2 +I 2 +2H 2 O→H 2 SO 4 +2HI . As the reaction proceeds, all available SO 2 will be consumed and the starch indicator added to the solution will bind with the unconsumed iodine, turning the solution black.
For simplicity, the equations will usually be written in terms of aqueous molecular iodine rather than the triiodide ion, as the iodide ion did not participate in the reaction in terms of mole ratio analysis. The disappearance of the deep blue color is, due to the decomposition of the iodine-starch clathrate, marks the end point.
This suggests that the starch probably acts as a reservoir for the iodine and iodide because of the starch-triiodide equilibrium, thereby modifying the kinetics of the steps in which iodine and iodide are involved. The reaction is "poisoned" by chloride (Cl −) ion, which must therefore be avoided, and will oscillate under a fairly wide range of
A redox titration [1] is a type of titration based on a redox reaction between the analyte and titrant. It may involve the use of a redox indicator and/or a potentiometer. 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.
Such a triglyceride has a high iodine value (approx. 119). Below, the reaction product after the addition of four equivalents of iodine or bromine to the four C=C double bonds of the unsaturated fatty acid residues. The determination of iodine value is a particular example of iodometry. A solution of iodine I 2 is yellow/brown in color.
Iodine monochloride and iodine monobromide may be prepared simply by reacting iodine with chlorine or bromine at room temperature and purified by fractional crystallisation. Both are quite reactive and attack even platinum and gold, though not boron, carbon, cadmium, lead, zirconium, niobium, molybdenum, and tungsten. Their reaction with ...