Potassium Iodide (CAS#7681-11-0)
Potassium iodide appears as white crystals, granules, or powder with a strong, bitter, saline taste. When exposed to bright light, it may gradually turn yellow due to photochemical decomposition that releases small amounts of free iodine. It is readily soluble in water, alcohol, acetone, and glycerol, and slightly soluble in ether and ammonia.
It can be prepared by reacting iodine with hot potassium hydroxide solution, followed by separation from the iodate by-product through fractional crystallization. In aqueous solution, potassium iodide can dissolve iodine to form the brown triiodide ion (I₃⁻).
The compound is widely used as an analytical reagent and in photography. It is also added to table salt to help prevent goiter and other disorders associated with iodine deficiency.
Chemically, potassium iodide is a metal iodide salt containing a potassium (K⁺) counterion. It acts as a hydroxyl radical scavenger and functions as an expectorant. As a non-radioactive source of iodine, it can help prevent the absorption of radioactive iodine (I-131) by the thyroid.
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Potassium iodide Chemical Properties
| Melting point | 681 °C (lit.) |
| Boiling point | 184 °C(lit.) |
| bulk density | 1500kg/m3 |
| density | 1.7 g/cm3 |
| vapor density | 9 (vs air) |
| vapor pressure | 0.31 mm Hg ( 25 °C) |
| refractive index | 1.677 |
| Fp | 1330°C |
| storage temp. | 2-8°C |
| solubility | H2O: 1 M at 20 °C, clear, colorless |
| pka | 0.06[at 20 ℃] |
| form | particles (round) |
| color | Yellow |
| Specific Gravity | 3.13 |
| Odor | odorless |
| PH | 6.0-9.0 (25℃, 1M in H2O) |
| Flame Color | Violet or light purple |
| biological source | rabbit |
| Water Solubility | 1.43 kg/L |
| Sensitive | Hygroscopic |
| Merck | 147643 |
| Exposure limits | ACGIH: TWA 0.01 ppm |
| Dielectric constant | 5.12 |
| BCS Class | 1 |
| Stability: | Stable. Protect from light and moisture. Incompatible with strong reducing agents, strong acids, steel, aluminium, alkali metals, brass, magnesium, zinc, cadmium, copper, tin, nickel and their alloys. |
| Cosmetics Ingredients Functions | ANTIMICROBIAL |
| InChIKey | NLKNQRATVPKPDG-UHFFFAOYSA-M |
| LogP | -0.958 at 25℃ |
| CAS DataBase Reference | 7681-11-0(CAS DataBase Reference) |
| NIST Chemistry Reference | Potassium iodide(7681-11-0) |
| EPA Substance Registry System | Potassium iodide (7681-11-0) |
| Absorption | cut-off at 273nm in H2O at 1M |
Safety Information
| Hazard Codes | Xn |
| Risk Statements | 26 |
| Safety Statements | 22-36/38 |
| WGK Germany | 1 |
| RTECS | TT2975000 |
| F | 10 |
| TSCA | TSCA listed |
| HS Code | 28276000 |
| Hazardous Substances Data | 7681-11-0(Hazardous Substances Data) |
| Toxicity | Approx LD i.v. in rats: 285 mg/kg (Hildebrandt) |
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Product Application of Potassium Iodide (CAS#7681-11-0)
Potassium iodide was initially employed as the primary halide in Talbot’s calotype process, later in the albumen-on-glass technique, and subsequently in the wet collodion process. It has also served as a secondary halide in silver bromide gelatin emulsions. In addition, it is used in animal feed, as a catalyst, in photographic chemicals, and for sanitation purposes.
Industrial production involves reacting potassium hydroxide with iodine, followed by purification through crystallization from water.
As an ionic compound, potassium iodide reacts with silver ions to form yellow silver iodide precipitate, which decomposes upon exposure to light and has been utilized in the production of high-speed photographic film. Silver nitrate can also be applied to detect the presence of iodide ions.
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