Photometric Determination of Iodine in Table Salt by Oxidative Color-fading Reaction of Alizarin Red with KIO3 Catalyzed by Potassium Bromide

In 0.3 mol·L-1 HCl medium,alizarin red was oxidized by KIO3 in the presence of KBr as catalyst,leading to decoloration of alizarin red.It was found that the magnitude of decrease in absorbance (ΔA) measured at 420 nm kept a linear relationship with the concentration of KIO3 in the range of 1.07-19.3 mg·L-1.Apparent molar absorptivity of the reaction system was found to be 2.47×104L·mol-1·cm-1.Based on these facts,a photometric method for determination of iodine in table salt was proposed.Salt samples were analyzed by the present method,giving values of recovery in the range of 95.1%-97.3%,and values of RSD′s (n=6) in the range of 3.4% to 4.2%.