Iā + 2 SāOāĀ²ā» ā 2 Iā» + SāOāĀ²ā»One mole diodine reacts with two moles of thiosulfate.
Use when: Respect iodine speciation and protocol conditions.
Iodometry and iodimetry
Distinguish between a direct titration of iodine and a titration of iodine released by an oxidant.
What is happening?
Iodimetry directly uses iodine as an oxidant of a reductant. In iodometry, an oxidant first releases iodine from iodide; this iodine is then dosed with thiosulfate.
Starch forms a colored complex with iodine species. In a thiosulfate assay, its disappearance near the end signals the consumption of iodine, under the conditions provided for by the method.
The formulas, with their conditions.
n(Iā) = c(thiosulfate) Ć Vā / 2c: mol/L; Vā: L; n: mol.
Use when: For the final titration step with thiosulfate.
Where is this principle used?
Disinfection plant
Control the oxidizing power of chlorinated products.
Food industry and mining laboratory
Dose certain reducing agents or oxidants using a suitable method.
What to observe in the experiment
Monitor the appearance then disappearance of the iodine color and relate the volume of thiosulfate to the quantity of iodine.
References and readings
This sheet explains the principles and their assumptions. Educational simulation can simplify the process; an industrial model requires suitable data and validation.
Have you understood the essentials?
Only one correct answer per question. Answer all three questions, then view the answer key.
Intu Lab Ā· Understanding sheet Ā· Kimba Christian