Analytical Method: Analytical Quality Assurance, Standard for Iodine

Reagents:
Cat.No. 102404  Potassium iodate volumetric standard
Cat.No. 105043  Potassium iodide for analysis
Cat.No. 109072  Sulfuric acid 0.5 mol/l
Cat.No. 109136  Sodium hydroxide solution 2 mol/l
Cat.No. 116754  Water for analysis
 
Preparation of a KlO₃ stock solution:
Dissolve 1.005 g of KlO₃ in 250 ml of distilled water in a calibrated or conformity-checked 1000-ml volumetric flask. Subsequently make up to the mark with distilled water.
 
Preparation of a KlO₃/Kl standard solution:
Transfer 5.60 ml of the KlO₃ stock solution to a calibrated or conformity-checked 1000-ml volumetric flask, add approx. 1g of Kl and make up to the mark with distilled water. 1 ml of this solution is equivalent to 0.020 mg of iodine.
 
Preparation of the iodine standard solution:
Pipette 10 ml KlO₃/Kl standard solution into a calibrated or conformity-checked 100-ml volumetric flask, add
2.0 ml of H₂SO₄  0.5 mol/l, leave to stand for 1 min, and then add NaOH 2 mol/l dropwise (approx. 1 ml) until the solution just loses its color. Subsequently make up the solution to the mark with distilled water. The concentration of the solution is 2.00 mg/l iodine.
 
Stability:
The KlO₃ stock solution remains stable for 4 weeks when stored in a cool place. The KlO₃/Kl standard solution can be used for 5 hours when stored in a cool place. The dilute iodine standard solution is not stable and must be used immediately.
 

Materials