The Briggs-Rauscher Reaction as a Model of a Chemical Clock
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| License | CC Attribution - NonCommercial - NoDerivatives 3.0 Germany: You are free to use, copy, distribute and transmit the work or content in unchanged form for any legal and non-commercial purpose as long as the work is attributed to the author in the manner specified by the author or licensor. | |
| Identifiers | 10.3203/IWF/C-1495eng (DOI) | |
| IWF Signature | C 1495 | |
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| Production Year | 1980 |
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| IWF Technical Data | Film, 16 mm, LT, 45 m ; F, 4 min |
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00:00
NitrosamineChemical reactionTiermodellChemical clock
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Chemical reactionOxideAcidChemical compoundBase (chemistry)IodineKaliumiodatChemical clockThermoformingHydrogen peroxideSetzen <Verfahrenstechnik>StarchPH indicatorConcentrateMultiprotein complexSolutionPermanganateSolubilitySulfateColourantManganesePerchloric acid
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NitrosamineHardnessWine tasting descriptorsColumbia Records
Transcript: English(auto-generated)
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The Briggs-Rocher reaction as model of a chemical clock. To initiate a Briggs-Rocher reaction, first make up three solutions.
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Solution A contains hydrogen peroxide. B is a solution of potassium iodate and perchloric acid. Solution C contains malonic acid, manganese sulfate and soluble starch.
00:44
As soon as the reactants mix, the chemical reaction begins. The colorless solution turns golden brown. Then it changes to deep blue, an indication of the formation of a starch-iodine complex.
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In the further course of the reaction, the blue color disappears, the solution becomes colorless and the cycle is repeated again. During the reaction, individual reactants are used up, bubbles of gas are produced, CO2 is released.
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The concentrations of the reactants change periodically.
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When the experiment is repeated, speeded up eight times, the oscillations are more clearly apparent.
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Towards the end, the reaction velocity decreases. Finally, the solution remains blue.
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The third experiment at double speed. The oscillations are due to autocatalytic reactions. The intermediate compounds produced periodically change their state of oxidation.
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Iodine is alternately produced and used up. The periodical occurrence of a substance, for example the liberation of iodine,
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determines the time pulse of the oscillation. This forms the time base of our chemical clock.