So for my IA, I dissolved a 1000mg vitamin c tablet in 355mL of water, took 20mL of it and diluted it to 100mL making it about 0.0032mol/L. I then added 5mL of 0.5mol/L potassium iodide, 5mL of 1.0mol/L hydrochloric acid and some 6 drops of 1 gram of starch dissolved in 100mL of water. I then titrated that entire sample with potassium iodate to determine the concentration of vitamin c. The endpoint was suppose to be when the solution turned blue (iodine+starch) but it ended up slowly turning yellow and then becoming darker until it eventually turned red. I tried increasing the concentration of potassium iodate but it just lead to the solution becoming red faster. I think I should have enough I had quit my IA and am excpected to redo it sometime later. Does anyone have any idea what has happened to my experiment? Any help would be appreciated. Thanks!