Vitamin C, also known as ascorbic acid (see Figure 1), is an essential nutrient in the human diet. Vitamin C is used in several metabolic processes and is a cofactor for many important enzymes in the body. In addition, vitamin C is a powerful antioxidant that helps protect the body from disease. Minor deficiencies in vitamin C can cause a multitude of side effects, and major deficiencies can result in scurvy, a disease characterized by tiredness, joint and muscle pain, and bleeding gums. Before the disease was understood, sailors who were at sea for several months would develop scurvy unless lemons and limes were on board. Because vitamin C is water soluble, it is not made by or stored in the body. Excess vitamin C cannot be saved in the tissues and is simply excreted in the urine, so this nutrient must be consumed daily as part of a healthy diet. Good dietary sources of vitamin C include fruits, such as strawberries and mangoes, and green vegetables, such as broccoli, leafy greens, and Brussels sprouts.
Chemical structure of ascorbic acid (vitamin C)
Because of the importance of vitamin C to a balanced diet, some food manufacturers add ascorbic acid to their products. Even though oranges contain a great deal of natural vitamin C, producers of orange juice commonly add ascorbic acid in order to raise the nutritional value. The amount of vitamin C in orange juice is reported on the nutrition label (see Figure 2). In this experiment, you will extract vitamin C from different brands of orange juice. You will use the technique of titration, a method of analysis used to find the exact quantity of a reactant in a titration flask. A burette is a calibrated tube with a stopcock that can be used to deliver a reactant to the flask.
|Data Table 2|
|Brand||Trial 1||Trial 2||Trial 3||Trial 4||Av. of two best trials|
|Readings start/end||Am. of iodine||Readings start/end||Am. of iodine||Readings start/end||Am. of iodine||Readings start/end||Am. of iodine|
|Data Table 1|
|Brand of orange juice||Amount of vitamin C (from label)|