Photometric Determination of Iodine in Table Salt by Oxidation Decoloration of Alizarin Purple

Based on the color-fading of alizarin purple by oxidation with iodate in a H2SO4 solution of ca. 0.1 mol·L-1,a photometric method for determination of iodine in table salt was proposed. The magnitude of decrease in absorbance (ΔA) was found to keep linear relationship with concentration of iodine in the range within 50.0 mg·L-1 as measured at the absorption maximum of 456 nm. Test for recovery was made by standard addition method and value of average recovery obtained was 104.5%. Precision was tested at 5 different concentration levels for 6 determinations,values of RSD′s found were all less than 1%.