I'm doing a science project using cooking oils and iodine. The iodine is to be a 7% tincture and a purple color. Where can i get this? Here is the procedure: Measure 20 mL of each vegetable oil with a graduated cylinder.2. Pour the oils into their respective beakers. 3. Put 3 drops of the 7% tincture of iodine into first oil, using the eyedropper, and immediately start the stopwatch. 4. Record how long it takes for the iodine coloring to disappear (in seconds) from the oil. 5. Repeat steps 2 and 3 for the other 4 oils6. Do 10 more trials. I'm using sunflower, safflower, ricebran, sesame, and corn oil. i'm not sure with iodine tincture is going to have a purple color andwill dissolve into the oils. Please help this is due VERY SOON. thanks!!!!!

Expert Answers

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This is a great science experiment.  Iodine reacts with the carbon-carbon double bonds in unsaturated fats but will not react with carbon-carbon single bonds in saturated fats.  So adding iodine to a number of different cooking oils and measuring the time it takes for the color to disappear will show which oils have the highest and lowest amounts of saturated fats versus unsaturated fats.  Iodine (I2) itself is a dark colored solid by nature and so it is sold commercially as a tincture, or a diluted solution in water and alcohol, usually with other inorganic salts present to help with solubility.  The salts are colorless so they will not affect anything.  The amount of actual iodine present can range from 2% to 10% depending on the brand.  The exact percentage of iodine is not that important but the higher the percentage the darker the color will be so the easier it will be to watch its color disappear in the experiment.  Iodine tinctures are sold at any drugstore.  The ingredient label will state the iodine percentage.

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