Povidone-iodine is a chemical complex of povidone, hydrogen iodide, and elemental iodine. Iodised salt is fortified with iodine in the form of sodium iodide. It is formed by combining aqueous solutions of iodide salts and iodine. The hydrogen iodide (HI) is reacted with chlorine to precipitate the iodine. Rhodium chloride in the presence of lithium iodide is employed as catalysts. Iodized salt, containing potassium iodide, is widely available. The simplest compound of iodine is hydrogen iodide, HI. Iodine, methyl iodide, and 1,2-dibromoethane are common activating agents. To this is added a solution containing potassium iodide, sodium thiosulfate, and starch. Common methylating agents are dimethyl sulfate, methyl iodide, and methyl triflate. The solubility of halide salts increases from fluoride to iodide. The potassium iodide in iodized salt is insufficient for this use. Solution routes to formaldehyde also entail oxidation of methanol or methyl iodide. Silver can be passivated by exposition to iodine vapors, forming a layer of silver iodide. The reaction rate is influenced by the reactivity of halogens, iodide and bromide being favored.