Relevance of Iodine Test in Product Demo
Curiosity is a process of learning. Maybe due to this, I usually study and do some research on everything I felt curious about. To tell you readers a story, I went to Amway product class on Monday night at Wangsa Maju. It's really an eye-opening session whereby product demo has been conducted by an expert. I was once a student of science stream in my good year of high school, so it's not an issue to understand some food facts. The presenter used glass filled with clear water and a drop of iodine to show the goodness of Nutrilite. These tools are essential before he put other element to test. Sadly, I forgot the importance of iodine usage in the demo. So, I google-d it today. Below are the facts of iodine test:
Iodine Test
The Iodine test is used to test for the presence of Starch. Iodine solution produced when it dissolved in an aqueous solution of potassium iodide - reacts with starch producing a blue black color.
This reaction is the result of the formation of poly iodide chains from the reaction of starch and iodine. The amylase, or straight chain portion of starch, forms helices where iodine molecules assemble, forming a dark blue/black color. The amylopectin, or branched portion of starch, forms much shorter helices and iodine molecules are unable to assemble, leading the color to be of an orange/yellow hue. As starch is broken down or hydrolyzed into smaller carbohydrate units, the blue-black color is not produced. Therefore, this test can determine completion of hydrolysis when a color change does not occur.
Iodine solution will also react with glycogen, although the color produced is browner and much less intense.
Ref: Wikipedia (2010). Iodine test. Web. url: http://en.wikipedia.org/wiki/Iodine_test
How Does Starch Indicates Iodine?
What properties of starch (given its chemical structure) allow it to be used as an indicator?
Davender Khera, Yale University
When starch is mixed with iodine in water, an intensely colored starch/iodine complex is formed. Many of the details of the reaction are still unknown. But it seems that the iodine (in the form of I5- ions) gets stuck in the coils of beta amylose molecules (beta amylose is a soluble starch). The starch forces the iodine atoms into a linear arrangement in the central groove of the amylose coil. There is some transfer of charge between the starch and the iodine. That changes the way electrons are confined, and so, changes spacing of the energy levels. The iodine/starch complex has energy level spacings that are just so for absorbing visible light- giving the complex its intense blue color.
The complex is very useful for indicating redox titrations that involve iodine because the color change is very sharp. It can also be used as a general redox indicator: when there is excess oxidizing agent, the complex is blue; when there is excess reducing agent, the I5- breaks up into iodine and iodide and the color disappears.
Starch Indicator
Starch is often used in chemistry as an indicator for redox titrations where iodine is present. Starch forms a very dark blue-black complex with iodine. The indicator is not affected by the presence of iodide (I-). In order for the the starch solution to change colour, both starch and iodide must be present. Starch forms an unstable complex (blue colored) in low concentrations of iodine. However, this complex is highly stable in high concentrations of iodine (it can't be decolourised and it spoils the reaction medium). So the iodine must be diluted first with the titrant (thiosulphate) then the starch is added, and the titration process is resumed taking into account the amount of thiosulphate added before adding the starch. Starch indicator solutions may be prepared in the laboratory. Alternatively, commercially available preparations are available.
Ref: Wikipedia (2010). Starch Indicator. Web. url: http://en.wikipedia.org/wiki/Starch_indicator
Oxidizing Agent
An oxidizing agent (also called an oxidant, oxidizer or oxidiser) can be defined as either: a chemical compound that readily transfers oxygen atoms, or a substance that gains electrons in a redox chemical reaction. In both cases, the oxidizing agent becomes reduced in the process.
In simple terms:
- The oxidizing agent is reduced.
- The reducing agent is oxidized.
- All atoms in a molecule can be assigned an oxidation number. This number changes when an oxidant acts on a substrate.
- Redox reactions occur when oxidation states of the reactants change.
Ref: Wikipedia (2010). Oxidizing Agent. Web. url: http://en.wikipedia.org/wiki/Oxidizing_agent
Back to my story, the presenter showed how M***i Mee turned the clear water into black colored solution. The magic part is when she put Bio C pill (Nutrilite product) into it, the water became clear once again. This experimental demo shows that M***i Mee (junk food etc.) absorbed into human blood stream as toxic waste once digested. Still, the importance of Bio C (Nutrilite) is to clear the waste from body and thanks to Amway, we can now enjoy a good life!
Note: Some info may differs due to language translation.
Davender Khera, Yale University
When starch is mixed with iodine in water, an intensely colored starch/iodine complex is formed. Many of the details of the reaction are still unknown. But it seems that the iodine (in the form of I5- ions) gets stuck in the coils of beta amylose molecules (beta amylose is a soluble starch). The starch forces the iodine atoms into a linear arrangement in the central groove of the amylose coil. There is some transfer of charge between the starch and the iodine. That changes the way electrons are confined, and so, changes spacing of the energy levels. The iodine/starch complex has energy level spacings that are just so for absorbing visible light- giving the complex its intense blue color.
The complex is very useful for indicating redox titrations that involve iodine because the color change is very sharp. It can also be used as a general redox indicator: when there is excess oxidizing agent, the complex is blue; when there is excess reducing agent, the I5- breaks up into iodine and iodide and the color disappears.
Ref: Fred Senese (2010). How does starch indicate iodine?. General Chemistry Online!. Web. url: http://antoine.frostburg.edu/chem/senese/101/redox/faq/starch-as-redox-indicator.shtml
Starch Indicator
Starch is often used in chemistry as an indicator for redox titrations where iodine is present. Starch forms a very dark blue-black complex with iodine. The indicator is not affected by the presence of iodide (I-). In order for the the starch solution to change colour, both starch and iodide must be present. Starch forms an unstable complex (blue colored) in low concentrations of iodine. However, this complex is highly stable in high concentrations of iodine (it can't be decolourised and it spoils the reaction medium). So the iodine must be diluted first with the titrant (thiosulphate) then the starch is added, and the titration process is resumed taking into account the amount of thiosulphate added before adding the starch. Starch indicator solutions may be prepared in the laboratory. Alternatively, commercially available preparations are available.
Ref: Wikipedia (2010). Starch Indicator. Web. url: http://en.wikipedia.org/wiki/Starch_indicator
Oxidizing Agent
An oxidizing agent (also called an oxidant, oxidizer or oxidiser) can be defined as either: a chemical compound that readily transfers oxygen atoms, or a substance that gains electrons in a redox chemical reaction. In both cases, the oxidizing agent becomes reduced in the process.
In simple terms:
- The oxidizing agent is reduced.
- The reducing agent is oxidized.
- All atoms in a molecule can be assigned an oxidation number. This number changes when an oxidant acts on a substrate.
- Redox reactions occur when oxidation states of the reactants change.
Ref: Wikipedia (2010). Oxidizing Agent. Web. url: http://en.wikipedia.org/wiki/Oxidizing_agent
Back to my story, the presenter showed how M***i Mee turned the clear water into black colored solution. The magic part is when she put Bio C pill (Nutrilite product) into it, the water became clear once again. This experimental demo shows that M***i Mee (junk food etc.) absorbed into human blood stream as toxic waste once digested. Still, the importance of Bio C (Nutrilite) is to clear the waste from body and thanks to Amway, we can now enjoy a good life!
Note: Some info may differs due to language translation.
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