iodine
iodien · HX968 · Iodine · Iodine base · iodine（imported） · TIANFU-CHEM Iodine · Iodine test solution · Iodide (I21-) (8CI,9CI)
Identifikatoren & physikalische Daten
| CAS No. | 12190-71-5 |
|---|---|
| Summenformel | I2 |
| Durchschnittliche Molmasse | 253,81 g/mol |
| SMILES | II |
| InChIKey | PNDPGZBMCMUPRI-UHFFFAOYSA-N |
Chemische & physikalische Eigenschaften
| Spezifische Wärmekapazität | Cp(crystal): 0.21 J/(g·K)Cp(gas): 0.15 J/(g·K), at 25℃ |
|---|---|
| Dielektrizitätskonstante | 11.0(Ambient) |
| InChI | InChI=1S/I2/c1-2 |
| InChIKey | PNDPGZBMCMUPRI-UHFFFAOYSA-N |
| SMILES | II |
| CAS Datenbank | 12190-71-5 |
Sicherheit & Vorschriften
| UN-Transportnummer | UN 3495 |
|---|---|
| Gefahrenklasse | 8 |
| Verpackungsgruppe | III |
Anwendungen & Verwendung
Beschreibung
Iodine, (I), is a nonmetallic element of family seven, the halogens. It is heavy, grayish-black in color, has a characteristic odor, and is readily sublimed to a violet vapor. It has a vapor density of 4.98, which is heavier than air. It melts at 236°F (113.5°C), has a boiling point of 363°F (184°C), and is insoluble in water. Iodine is toxic by ingestion and inhalation, and is a strong irritant to eyes and skin. The TLV ceiling is 0.1 ppm in air. Iodine is used for antiseptics, germicides, x-ray contrast material, food and feed additives, water treatment, and medicinal soaps. The four-digit UN identification number for iodine is only for the compounds iodine monochloride and iodine pentafluoride, and they are 1792 and 2495, respectively. The DOT lists iodine monochloride as a Class 8 corrosive, and iodine pentafluoride carries an oxidizer and poison label. Iodine does not have an NFPA 704 designation.
Occurrence
Iodine is the 64th most abundant element on Earth. It occurs widely over the Earth, butnever in the elemental form and never in high concentrations.It occurs in seawater where some species of seaweed and kelp accumulate the elementin their cells. It is also recovered from deep brine wells found in Chile, Indonesia, Japan,and Michigan, Arkansas, and Oklahoma in the United States. The iodine is recovered fromcremated ashes of seaweed. The ashes are leached with water to remove the unwanted salts.Finally, manganese dioxide (MnO2) is added to oxidize the iodine ions (I1-) to produceelemental diatomic iodine (I2). The following reaction takes place: 4I1- + MnO2 → MnI2 +I2 + 2O2-.Chilean saltpeter [potassium nitrate (KNO3)] has a number of impurities, includingsodium and calcium iodate. Iodine is separated from the impurities and, after being treatedchemically, finally produces diatomic iodine. Today, iodine is mostly recovered from sodiumiodate (NaIO3) and sodium periodate (NaIO4) obtained from Chile and Bolivia.
History
Iodine was first discovered by Barnard Courtois, a French chemist in 1811 while extracting potassium and sodium from seaweed ash. When he accidentally added sulfuric acid, a violet colored cloud evolved from the mass. The resulting gas was condensed into dark crystals-the first occurrence of observed solid iodine.Courtois analyzed them and then gave some of them to a fellow chemist, Joseph Louis Gay-Lussac, for further study.Two years later, Gay-Lussac presented his study to the scientific community, announcing the discovery of a new element that he named "iodine," after the Greek word "ioeides" meaning violet colored.A Swiss physician by the name of J.F. Coindet had previously used burnt sponge and seaweed for the treatment of goiter (an enlargement of the thyroid gland). This treatment had been in use since 3600 B.C., when it appeared in Chinese medical writings, as well as writings by the Greek physician Hippocrates. Upon hearing of the work of Courtois and Gay-Lussac, Coindet suspected that iodine might be the active ingredient in seaweed that cured goiter. In 1819, he successfully tested a tincture of iodine on 150 patients, significantly reducing the size of their goiter within one week. As a result of these early studies, in the 1830s the medical community started advocating for iodine supplements to decrease the occurrence of goiter.
Verwenden
Iodine is a halogen element extracted from chilean nitrate-bearing earth or from seaweed. it functions by its presence in the thyroid hormones. iodine deficiency is associated with goiter. sources are potassium and cuprous iodide and potassium and calcium iodate, of which the iodate form is preferred because of better stability. it is used as a food supplement.
Herstellung & Synthese
synthetische
If extreme purification is unnecessary, commercial iodine or iodine regenerated from wastes can, according to a method described by Plotnikow, be sublimed, first over KI and then over BaO. It is then stored in ground glass containers placed in a desiccator over P2O5.