Iodine Titration Methods
Titration is a method used to determine the concentration of a compound in solution. A compound in a solution of known concentrate is added to the unknown solution. The two compounds react, and when the reaction is complete, it's possible to calculate the volume of the unknown solution. Iodine is a useful compound for performing titrations.
Vitamin C
An unknown concentration of vitamin C or ascorbic acid can be determined using iodine. When ascorbic acid comes into contact with iodine, the chemical reaction that occurs produces dehydroascorbic acid and iodide. A starch indicator is added to the vitamin C solution to indicate when the chemical reaction is complete. As long as there is still ascorbic acid in the solution, the iodine will react with it and become iodide. When all the ascorbic acid has reacted and become dehydroascorbic acid, the iodine will react with the starch to create a dark blue color, signaling the reaction is complete. The dehydroascorbic acid can be measured to determine the concentration of vitamin C in the original solution.
Thiosulphate
The concentration of sodium thiosulphate in solution can be determined using an iodine titration. An iodine solution added to a sodium thiosulphate solution of unknown concentration will create oxidized iodine and tetrathionate ions. Starch is added to the sodium thiosulphate solution. Iodine is then added slowly. The solution will turn a dark blue color. When the disappears, it indicates the reaction is complete and the concentration of soduium thiosulphate can be calculated from the amount of tetrathionate ions that are produced and the amount of iodine solution used.
Copper in Superconductors
Iodine titration can also be used to calculate the amount of copper in high temperature superconductors, but the process is more involved than the simple titrations used to determine ascorbic acid concentration or sodium thiosulphate concentration. A double titration process is used. The chemical potassium thiocyanate is used release absorbed iodine to continue the chemical reaction. Molecules made up of hydrogen, nitrogen and fluorine are used to prevent interference from impurities within the superconductor structure. The resulting chemical reaction can determine copper valence atoms within the superconductor material.
Tags: ascorbic acid, chemical reaction, reaction complete, sodium thiosulphate, dark blue, dehydroascorbic acid