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starch-iodine

English translation: see

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05:23 Jun 24, 2004
English to English translations [Non-PRO]
Science - Biology (-tech,-chem,micro-) / carbohydrate chemistry
English term or phrase: starch-iodine
Iodine test for the determination of starches
S.A. Nagra
English translation:see
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.
Selected response from:

Maria Luisa Duarte
Spain
Local time: 11:21
Grading comment
Graded automatically based on peer agreement.
4 KudoZ points were awarded for this answer

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Summary of answers provided
5 +3see
Maria Luisa Duarte
4 +1a complex of starch and iodine
Saleh Chowdhury, Ph.D.


Discussion entries: 1





  

Answers


1 hr   confidence: Answerer confidence 4/5Answerer confidence 4/5 peer agreement (net): +1
a 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#...
Saleh Chowdhury, Ph.D.
Bangladesh
Local time: 15:21
Native speaker of: Native in BengaliBengali

Peer comments on this answer (and responses from the answerer)
agree  Ramesh Madhavan
2 hrs
  -> Thanks Ramesh
Login to enter a peer comment (or grade)

1 hr   confidence: Answerer confidence 5/5 peer agreement (net): +3
see


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
Maria Luisa Duarte
Spain
Local time: 11:21
Native speaker of: Native in EnglishEnglish, Native in PortuguesePortuguese
Grading comment
Graded automatically based on peer agreement.

Peer comments on this answer (and responses from the answerer)
agree  Vicky Papaprodromou
2 hrs

agree  Jörgen Slet
1 day33 mins

agree  Nanny Wintjens
6 days
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