Iodine-131 and/or worsen hyperthyroidism and hypothyroidism respectively, and ultimately cause temporary or even permanent thyroid conditions. It can also cause sialadenitis (an inflammation of the salivary gland), gastrointestinal disturbances, allergic reactions and rashes. Potassium iodide is also not recommended for those who have had an allergic reaction to iodine, and people with dermatitis herpetiformis and hypocomplementemic vasculitis, conditions that are linked to a risk of iodine sensitivity. The use of a particular "iodine tablet" used in portable water purification has also been determined as somewhat effective at reducing radioiodine uptake. In a small study on human subjects who, for each of
Iodine 1% of a sample of gaseous iodine at atmospheric pressure is dissociated into iodine atoms at 575 °C. Temperatures greater than 750 °C are required for fluorine, chlorine, and bromine to dissociate to a similar extent. Most bonds to iodine are weaker than the analogous bonds to the lighter halogens. Gaseous iodine is composed of I molecules with an I–I bond length of 266.6 pm. The I–I bond is one of the longest single bonds known. It is even longer (271.5 pm) in solid orthorhombic crystalline iodine, which has the same crystal structure as chlorine and bromine. (The record is