ANION exchange resins have been used to separate organic and inorganic iodine compounds from thyroid extracts and from serum by various workers1–4. Organic iodine compounds are relatively easily eluted from resins of this type, but it has proved difficult to recover the iodide. Attempts have been made to do this with sodium bromide by Galton and Pitt-Rivers1 and with sodium sulphate by Sekino et al.5.