The Colorimetric Determination of Small Amounts of Iodide, with Special Reference to the Determination of Iodide in the Presence of Organically-Bound Iodine

Abstract A photocolorimetric method has been developed for the determination of small quantities of inorganic iodide in the presence of organically-bound iodine. The iodide-containing solution is treated with a mixed iodate-starch solution at an appropriate pH, when a stable blue colour is produced. The relationship between concentration of iodide and optical density is linear. The effect of various salts on the reaction has been investigated; the analytical application of the method to some iodine-containing drugs and pharmaceutical preparations has been studied. The reason for the failure of the colour reaction to obey Beer's law is discussed.