Iodine in Table Salt

Reagents

Product No. 105445 Zinc iodide starch solution
Product No. 100716 Sulfuric acid 25 % for analysis
Product No. 116754 Water for analysis

Measurement Range

0.50 - 3.00 mg/L iodate at cell length 10 mm and 585 nm
Iodinated table salt contains 25 - 30 mg/kg of potassium iodate. This is added to prevent iodine deficiency disease of the thyroid. The daily recommended dose of iodine for adults is 150 - 200 mg.

Sample Preparation

The sample should be dried to constant weight at 105 °C and 10 g dissolved in water in a 100-mL volumetric flask and made up to the mark with water for analysis.

Analysis

Add 1.0 mL zinc iodide starch solution and 0.20 mL sulphuric acid 25 % to 20 mL sample. Allow to stand for 10 minutes and measure against a blank comprising equal portions of water for analysis and reagents at 585 nm in a 10 mm rectangular cell.

Calculation

Iodate content in mg/kg = analysis value in mg/L x 10

Calculation when measuring the absorbance value using the photometer SQ118 without programming the method in the memory of the instrument: