   #copyright

Potassium iodide

2007 Schools Wikipedia Selection. Related subjects: Chemical compounds

                          Potassium iodide
                          Potassium iodide
                               General
       Systematic name                               Potassium iodide
           Other names                                 Kalium iodide,
                                                     knollide, potide
     Molecular formula                                             KI
            Molar mass                                   166.00 g/mol
            Appearance                        white crystalline solid
            CAS number                                    [7681-11-0]
                             Properties
     Density and phase                             3.13 g/cm^3, solid
   Solubility in water                            128 g/100 ml (6 °C)
         Melting point                                 681 °C (954 K)
         Boiling point                               1330 °C (1600 K)
       Acidity (pK[a])                                              ?
    Alkilinity (pK[b])                                              ?
                              Structure
       Molecular shape                                              ?
 Coordination geometry                                              ?
     Crystal structure                                              ?
         Dipole moment                                            ? D
                               Hazards
                  MSDS                                  External MSDS
          Main hazards                             Slightly hazardous
              NFPA 704

                       0
                       1
                       0

         R/S statement                           R: 36, 38, 42-43, 61
                                                 S: 26, 36-37, 39, 45
          RTECS number                                      TT2975000
                       Supplementary data page
Structure & properties                                  n, ε[r], etc.
    Thermodynamic data                                Phase behaviour
                                                   Solid, liquid, gas
         Spectral data                                UV, IR, NMR, MS
                          Related compounds
          Other anions                              potassium bromide
                                                   potassium chloride
         Other cations                   lithium iodide
                                         sodium iodide
                                         rubidium iodide
                                                       caesium iodide
          Except where noted otherwise, data are given for
               materials in their standard state (at 25 °C, 100 kPa)
                                    Infobox disclaimer and references

   Potassium iodide is a white crystalline salt with chemical formula KI,
   used in photography and radiation treatment. It finds widespread
   application as an iodide source because it is less hygroscopic than
   sodium iodide, making it easier to work with. KI can turn yellow upon
   heating in air or upon standing in moist air for long periods, because
   of oxidation of the iodide to iodine.

Chemical properties

   Potassium iodide behaves as a simple ionic salt, K^+I^−. Since the
   iodide ion is a mild reducing agent, I^− is easily oxidised to I[2] by
   powerful oxidising agents such as chlorine:

   2 KI( aq) + Cl[2](aq) → 2 KCl + I[2](aq)

   Even air will oxidize iodide as evidenced by the observation of a
   purple extract when KI is rinsed with dichloromethane. Under acidic
   conditions, KI is oxidised even more easily, due to the formation of
   hydroiodic acid (HI), which is a powerful reducing agent.

   KI forms I[3]^− when combined with elemental iodine.

                KI(aq) + I[2]( s) → KI[3](aq)

   Unlike I[2], I[3]^− salts can be highly water-soluble. I[2] and I[3]^−
   have virtually identical redox potentials (0.535 and 0.536 V vs NHE,
   respectively), i.e. they are both mild oxidants relative to H[2].
   Therefore, this reaction allows the iodine to be used in aqueous
   solutions for redox titrations.

   Potassium iodide also serves in some organic reactions as a source of
   iodide ion (see "uses" below).

Preparation

   Potassium iodide may be prepared by the reaction of a potassium base
   with hydroiodic acid, for example:

   HI + KHCO[3] → KI + H[2]O( l) + CO[2](g)

   Alternatively iron(II) iodide, prepared using scrap iron and iodine
   (made from iodide rich brines or from Chile saltpeter, can be treated
   with potassium carbonate:

   FeI[2] + K[2]CO[3] → 2 KI + FeCO[3]

Uses

   Potassium iodide is used in photography, in the preparation of
   silver(I) iodide for high speed photographic film:

   KI( aq) + AgNO[3]( aq) → AgI( s) + KNO[3]( aq)

   Potassium iodide is also added to table salt in small quantities to
   make it "iodized". In a saturated solution, it is also used as an
   expectorant to treat lung congestion.

   KI is often used as a source of iodide ion in organic synthesis. A
   useful application is in the preparation of aryl iodides from
   arenediazonium salts^, for example:

   Saturated solution of potassium iodide is also used as treatment for
   sporotrichosis, a fungal infection.

   In medical use, it can also serve as an antiseptic for people suffering
   from sore throat. The dose is 0.5g-1.0g in 100mL, with the accompany of
   iodine (0.5g-1.0g in 100mL).

Role of potassium iodide in radiological emergency preparedness

   An unopened box of Potassium iodate tablets, produced and distributed
   to the population of the Republic of Ireland following a preparedness
   scandal relating to the Sellafield nuclear power station in the United
   Kingdom.
   Enlarge
   An unopened box of Potassium iodate tablets, produced and distributed
   to the population of the Republic of Ireland following a preparedness
   scandal relating to the Sellafield nuclear power station in the United
   Kingdom.

   Potassium iodide may also be used to protect the thyroid from
   radioactive iodine in the event of an accident or attack at a nuclear
   power plant, or other nuclear attack, especially where a nuclear
   reactor is breached and the volatile radionuclides, which contain
   significant amount of ^131I, are released into the environment.
   Radioiodine is a particularly dangerous radionuclide because the body
   concentrates it in the thyroid gland. Potassium iodide cannot protect
   against other causes of radiation poisoning, however, nor can it
   provide any degree of protection against a dirty bomb unless the bomb
   happens to contain a significant amount of radioactive iodine. In case
   of a nuclear emergency, iodine used for the cleaning of wounds should
   not be ingested. It is a poison.

   CAPTION: Recommended Dosage for Radiological Emergencies involving
   radioactive iodine ^

          Age        KI in mg KIO3 in mg
   Over 12 years old 130      170
   3 - 12 years old  65       85
   1 - 36 months old 32       42
   < 1 month old     16       21

   See fission products and the external links for more details.

Precautions

   Mild irritant, wear gloves. Chronic overexposure can have adverse
   effects on the thyroid.
   Retrieved from " http://en.wikipedia.org/wiki/Potassium_iodide"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
