Spectrophotometric determination of iodine in salt adding iodine by decoloration of methylene blue

In the medium of H2SO4 and in the presence of KBr,the color of methylene blue oxidized by iodate can be faded,and the degree of color fading is proportional to the concentration of iodate,and a new spectrophotometric method for determination of iodine is reported.The maxium absorbance is at 590 nm.Beer′s law is obeyed from 1 to 20 μg of iodine per 10 mL of solution.The apparent molar absorptivity is 1.0×104 L·mol-1·cm-1.The method has been used in the determination of iodine in iodine-spiked salt with satisfactory results.