Preparation of titrant I₃^- from the generating agent KIO₃

Using a volumetric pipet, pipet exactly 10.0 mL of a 0.0100 M KIO₃ solution into a 100 mL volumetric flask. Add 20 mL of 0.30 M H₂SO₄, and approximately

0.40 g of KI. Shake until homogeneous and dilute to the mark.

Sample Preparation of Fruits and Vegetables

Weigh out approximately 3 g of fruit or vegetable on the top loading balance. Be sure to record the weight of the sample. Place the sample into a mortar along with 15 mL of 0.30 M sulfuric acid. Thoroughly grind and mix the heterogeneous mixture. Allow the sample to sit for 15 minutes and then decant the liquid into a 125 mL Erlenmeyer flask. Carry out two more extractions of Vitamin C from the sample by adding approximately 15 mL of deionized water to the residue in the mortar, grinding the mixture, and decanting the solution into the 125 mL Erlenmeyer flask. When the extraction has been completed, the solution volume should be approximately 45 mL. Samples should be prepared in triplicate. Titration of the first sample should be done rapidly to obtain the approximate amount of titrant required to reach the endpoint. The remaining samples should be titrated by adding titrant rapidly until the volume of titrant is approximately 5 mL short of the endpoint. At this point, addition of titrant is done dropwise until the endpoint is reached.