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# Determine the Amount of Vitamin C in Various Foods by Using Titration Method (page 2)

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Author: Janice VanCleave

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1. Analyze a multiple-vitamin tablet to determine the amount of vitamin C in it. Repeat the experiment substituting a multiple-vitamin tablet for the vitamin C tablet. Note: Avoid using a multiple vitamin that contains vitamin E, which may affect the results.
2. The number of drops of iodine needed to react with the vitamin C mixture depends on the size of the drops, which is determined by the eyedropper. Thus, the same size eyedropper must be used throughout the experiment. Use the following equation and the known number of drops of iodine required to react with 25 mg of vitamin C to compute the amount of vitamin C in the test material (the multiple-vitamin tablet). See Appendix 6 for an example calculation.

3. Determine the concentration of vitamin C in citrus fruit juices. Repeat the original experiment replacing the vitamin C solution with 1/2 cup (125 ml) of each fruit juice to be tested. If the juices contain pulp, strain them through cheesecloth before beginning the experiment. Again, use the equation comparing the drops of iodine needed to react with 25 mg of vitamin C to calculate the number of milligrams of the vitamin in each sample of fruit juice.
4. Does temperature affect the concentration of vitamin C? Repeat the original experiment twice, first substituting 25 ml of boiled orange juice for the standard vitamin C solution, and then using 1/2 cup (125 ml) of frozen orange juice that has been thawed. Use the equation again to compute the amount of vitamin C in the test solution.
5. Does storing orange juice in an open container affect the vitamin C content? Repeat the original experiment using 2 cups (500 ml) of orange juice prepared by diluting a small can of frozen orange juice according to the directions on the container. Pour 1 cup (250 ml) of orange juice into two separate jars. Place a lid on one container. Each day, test a 1/8 cup (31 ml) sample from each container.