All about iodine in 3 minutes HD

Iodine (I2) is a hard, lustrous, purplish-grey nonmetal that sublimes easily to form a purple gas. It dissolves easily in organic solvents such as ethanol. Iodine and its compounds are relatively rare – iodine is only the 61st most common substance in the earth’s crust. Iodine is one of the few simple substances capable of sublimating (passing straight from solid to gaseous form) under normal circumstances. This characteristic is widely applied both to purify iodine and to reveal fingerprints in criminal analysis. In addition to subliming, iodine dissolves easily in the fats in sweat traces and, as it gets “stuck” in these fats, reveals any fingerprints. History of discovery In 1811, Bernard Courtois accidentally used a higher concentration of sulfuric acid than usual while obtaining potassium nitrate from seaweed ash. A purple gas appeared, which condensed as purple crystals – iodine! However, Courtois didn’t pursue any study of this unfamiliar gas. A few years later, independently of one another, Humphry Davy and Joseph Louis Gay-Lussac proved that the gas Courtois discovered was in fact a new chemical element. They gave the new substance the now-familiar name of “iodine,” which means “purple” in Greek. Creation and chemical properties Iodine can be created in a laboratory by mixing solutions of potassium iodide (KI), hydrogen peroxide (H2O2), and citric acid (C6H8O7): 6KI + 3H2O2 + 2C6H8O7 → 3I2↓ + 2K3C6H5O7 + 6H2O Meanwhile, the resulting molecular iodine reacts with the remainder of potassium iodide to form potassium triiodide, which tints the solution a reddish-brown color: KI + I2 → KI3 Iodine is a relatively active nonmetal. It reacts vigorously with aluminum (Al) to form aluminum iodide (AlI3). The reaction is initiated by adding a few drops of water, in which iodine partially dissolves to form hydroiodic acid (HI) and hypoiodous acid (HIO). The resulting acids dissolve the oxide film on the surface of the aluminum, which then begins to react with iodine. The reaction is accompanied by an intense release of heat, which causes some of the iodine to sublime, forming a purple gas. I2 + H2O → HI + HIO Al2O3 + 3HI + 3HIO → AlI3 + Al(IO)3 + 3H2O 2Al + 3I2 → 2AlI3 As iodide ions are powerful reductive agents, potassium iodide (KI) reacts with copper sulfate solutions (CuSO4) to form copper(I) iodide (CuI) and molecular iodine. 4KI + 2CuSO4 → 2CuI↓ + I2↓ + 2K2SO4 Again, the resulting molecular iodine reacts with the remaining potassium iodide to create potassium triiodide, which tints the solution a reddish-brown color: KI + I2 → KI3 A solution can be tested for the presence of iodide ions using a qualitative reaction. Iodide ions react with a solution of silver nitrate (AgNO3), to produce a yellow precipitate of silver iodide (AgI). AgNO3 + KI → AgI↓ + KNO3 Another qualitative reaction used to test for the presence of iodide ions is the reaction known as “Golden Rain.” Mixing heated solutions of potassium iodide and le