starch-iodine
English translation: see
| 05:23 Jun 24, 2004 |
| English language (monolingual) [Non-PRO] Science - Biology (-tech,-chem,micro-) / carbohydrate chemistry | ||||
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|  Selected response from: Maria Luisa Duarte Spain Local time: 12:51 | |||
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| SUMMARY OF ALL EXPLANATIONS PROVIDED | ||||
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| 5 +3 | see |
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| 4 +1 | a complex of starch and iodine |
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| Discussion entries: 1 | |
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Answers
1 hr confidence: 
peer agreement (net): +1
peer agreement (net): +1a complex of starch and iodine Explanation: The standard test for starch is by application of an iodine solution. If starch is present in a solution, then after adding iodine, a strarch-iodine complex would form. The starch-iodine mixture turns dark blue. The darkness of the blue is a function of the starch (or iodine) concentration. The blue color means that a starch iodine solution transmits blue light better than other wavelengths (or that other wavelengths are absorbed to a greater degree than blue). Reference: http://xnet.rrc.mb.ca/martins/Biochem%202/Biochem2-Labs.htm#... |
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1 hr confidence: peer agreement (net): +3
peer agreement (net): +3see Explanation: Starch - Iodine Chemical Test for Starch or Iodine: Amylose in starch is responsible for the formation of a deep blue color in the presence of iodine. The iodine molecule slips inside of the amylose coil. Iodine - KI Reagent: Iodine is not very soluble in water, therefore the iodine reagent is made by dissolving iodine in water in the presence of potassium iodide. This makes a linear triiodide ion complex with is soluble. The triiodide ion ion slips into the coil of the starch causing an intense blue-black color. Starch Test: Add Iodine-KI reagent to a solution or directly on a potato or other materials such as bread, crackers, or flour. A blue-black color results if starch is present. If starch amylose is not present, then the color will stay orange or yellow. Starch amylopectin does not give the color, nor does cellulose, nor do disaccharides such as sucrose in sugar. Iodine Test: When following the changes in some inorganic oxidation reduction reactions, iodine may be used as an indicator to follow the changes of iodide ion and iodine element. Soluble starch solution is added. Only iodine element in the presence of iodide ion will give the characteristic blue black color. Neither iodine element alone nor iodide ions alone will give the color result. Reference: http://www.elmhurst.edu/~chm/vchembook/548starchiodine.html |
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