potassium iodide (KI) is a salt yodovodorodnoy acid.In appearance, it is a colorless solid crystal cubic crystals form.Potassium iodide in air when heated or exposed to light yellowing due to oxygen oxidation of iodine ions to elemental iodine.With increasing temperature the solubility of the salt in water increases.In 100 g of water was dissolved 128 g of the salt at 0 ° C, 145 g at 20 ° C, 176 g at 60 ° C, 209 g at 100 ° C.The molar mass of the compound is 166.00277 g / mol.The refractive index is 1.667.Density 3.13 g / cm³.Melting point 686 ° C.The boiling point of 1330 ° C.Potassium iodide less hygroscopic (absorbs water less readily) than sodium iodide, so it is easier to work with.
Potassium iodide is a mild reducing agent, it is easily oxidized chlorine: 2KI + Cl2 → 2KCl + I2.Reacts with iodine, the result is a Lugol: KI + I2 → KI3.Yodovodorodnoy acid potassium salt can be prepared by the reaction of iodine with potassium hydroxide 6KOH + 3I2 = 5KI + KIO3 + 3H2O or reduction of potassium iodate coal 2KIO3 + 3C = 2KI + 3CO2.Yellow salt expired indicates the oxidation of iodide to iodine by the reaction equation: 4KI + 2CO2 + O2 → 2K2CO3 + 2I2.
In nature, iodine is present everywhere, but it is a rare element, since its content in all natural sources is negligible.As with other halogens, characterized by a high reactivity, it is usually found in the form of compounds, namely, alkali metal iodides of sodium and potassium, but (unlike other halogen) also in the form of iodates, dissolved in water.However, there is never as nitrogen iodide (IN3), since it is very unstable and rapidly degraded from the blast connection.The ocean waters or from underground sources iodides and iodates contains approximately equal amounts.Since potassium iodide is soluble in water, iodine ions are present in the ocean, sea algae and sea fish.Seafoods are a major source of iodine into the human body, since they contain many times more iodine compounds than in living beings living on land.And the main raw material for the industrial production of iodine is drilling water or some type of algae.
potassium iodide contained in the drilling water used in the industry to produce iodine: KI + Cl2 → KCl2 + I2.Also, it is widely used as a source of iodide ions.In analytical chemistry, potassium iodide is used for redox iodometric titration.Paper moistened with a solution of salt and starch, helping qualitatively detect the presence of chlorine, ozone or other oxidants, which stands out in the presence of the combined iodine and starch coated on paper turns blue.Used as a food additive for animal feed and in human food: in small quantities, for preventing endemic (increase thyroid) disease, which often occur in some geographical areas due to natural deficiency of iodine, potassium iodide, along withpotassium iodate are added to table salt.The thus obtained food product is called iodized salt.Warranty storage period of such salts is limited, because over time, under the influence of an excess of oxygen and carbon dioxide, KI slowly oxidizes to a metal carbonate and elemental iodine, which is then evaporated.
In medicine, potassium iodide is used as a drug.Potassium iodide, is available in different dosage forms: tablets, oral solution, film coated tablets, eye drops, chewable tablets.Drugs make up for deficiency of iodine in the body, have antithyroid (in the thyroid gland inhibit the biosynthesis of hormones), mucolytic (liquefied lung mucus and facilitate its access), expectorant, anti-fungal, absorbing, radioprotective (protects the thyroid gland from radiation and prevents the absorption of its radioactive iodine) effect.The recommended dosage of WHO in emergencies involving radioactive iodine depends on age and is:
- for people over 12 years - 130 mg per day;
- from 3 to 12 years - 65 mg per day;
- aged 1 to 36 months - 32 mg per day;
- children under the age of 1 month - 16 mg per day.
WHO does not recommend taking potassium iodide prophylaxis for people older than 40 years.
