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

Table 1. Parameter list for programming the photometer SQ 118

Method	Iodate
Product No.	-------
Measuring Range	0.50 - 3.00
Units	mg/L
Reaction Time	10 0 min
Cell	10 mm
Wavelength	585 nm
Calibration	Factor
Evaluation	Linear
Factor	2.80

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

Measured absorbance of samples in A	Result in mg/l [A sample * 2.80]
1.000	2.80