Potassium iodide

Chemical properties

Colorless or white cubic crystals or granules; becomes yellowish when exposed to bright light due to photochemical decomposition liberating traces of free iodine; density 3.13 g/cm3; melts at 681°C; vaporizes at 1,330°C; highly soluble in water, ~140 g/100mL at 20°C; aqueous solution readily dissolves iodine; sparingly soluble in ethanol (about 2 g/100mL at 25°C) and acetone; slightly soluble in ether and ammonia.

Uses

Medical Uses

Nuclear radiation
Shortly before or after exposure to nuclear radiation, daily intake of 130 mg of potassium iodide (adults) can effectively prevent the absorption of radioactive iodine by the thyroid, thereby reducing the accumulation of radioactive iodine, and reducing impair of radioactive iodine to the thyroid gland and nearby tissues.


Dermatological Diseases
Sporotrichosis: Potassium iodide, used either alone or in combination, has a significant effect in the treatment of spore mycosis.
Hypertrophic scars: Potassium iodide solution can inhibit the hyperplasis of scar tissue, dissipate the granulation tissue, soften the scar, loosen the adhesion, and eliminate chronic inflammation.
Erythema nodosum: Potassium iodide deposits in granuloma that cause mast cells to release heparin, thereby inhibiting the occurrence of delayed allergy.

Ophthalmic Diseases
Cataract: Potassium iodide is one of the first drugs used to treat cataract. It is effective on lens regeneration and reducing lens epithelium damage in experimental naphthalene cataract.
Blepharitis: Application of 2% potassium iodide in eye skin is effective for styes patients with myosinosis, with a cure rate of 88.4%.
Vitreous opacity: Oral administration of 10% potassium iodide can effectively promote the bleeding in the vitreous body and absorption of exudate thus reducing the opacity of vitreous body.
Chronic bronchitis:10% potassium iodide solution has good efficaty in treating chronic bronchitis.
Lead nephropathy: Potassium iodide protects the renal cells from lead damage by either blocking lead diffusion or binding with lead in the cells as to protect the Na + -k + -atpase.
Hyperplasia of mammary glands: The small dose of potassium iodide can promote the secretion of luteinizing hormone in the anterior pituitary gland and promote the luteinization of the ovarian follicle, thus reducing the estrogen level and restoring the normal function of the ovary.

Others
In the treatment of temporomandibular joint disorders, periarthritis of shoulder, congenital muscular torticollis, cervical spondylosis vertigo, clinical studies have shown that applying potassium iodide can increase sympathetic nerve excitability, promote inflammation absorption, release the conglutination and soften the scar thus helping restore the functions of the nerve.

Adverse reactions

1. Allergy, not common. It can occur immediately after taking the drug, or an angioedema may occur several hours later. It may happen in the upper limbs, lower extremities, face, lips, tongue, or throat. It may also have erythema, fever, or discomfort.
    
2. Long-term use may cause oral, throat burning sensation, runny nose, metallic taste, tooth and gum pain, stomach discomfort, severe headache and other symptoms of iodine poisoning; hyperkalemia symptoms such as confusion, arrhythmia, numb and tingling feeling in hands and feet, and weakness of lower limbs may also occur. Stop taking medicine to subside.
    
3. Gastrointestinal adverse reactions such as diarrhea, nausea, vomiting, and stomach pain may occur, though uncommon.
    
4. Effects on thyroid function: Excessive iodine can cause hyperthyroidism or hypothyroidism. Recession or inhibition of thyroid function can lead to excessive secretion of TSH and even goiter.
    
5. Combination with anti-thyroid drugs may cause hypothyroidism and goiter; combination with angiotensin converting enzyme inhibitors or with potassium-sparing diuretics is prone to hyperkalemia, so potassium should be monitored in these cases; combination with lithium salts may cause hypothyroidism and goiter.

Feed additives

Potassium iodide is ionic compound which iodine ions and silver ions can form yellow precipitate silver iodide (when exposes to light, it can decompose, it can be used to make high-speed photographic film), silver nitrate can be used to verify the presence of iodine ions. Iodine is ingredient of thyroxine, it is closely related to basal metabolism livestock, it participates in almost all the metabolism process, livestock iodine deficiency can cause thyroid hypertrophy, basal metabolic rate dropps, and affects growth and development. Young animals and animal feed of iodine deficiency area need add iodine, iodine requirements of high producing dairy cows, yield hens should increase, the feed also need to add iodine. Iodine of milk and egg increases with dietary iodine. According to reports, periodate eggs can reduce cholesterol levels and good for the health of patients with hypertension. In addition, during the fattening of animals, though not iodine deficiency, in order to make livestock hypothyroidism strong, enhanced anti-stress, maintain the highest production capacity, iodide is also added, potassium iodide as the iodine source is added to feed, it can prevent iodine deficiency disorders, promote growth, increase egg production rate and reproduction rate and improve feed efficiency, the amount of feed is generally a few PPM, because of its instability, iron citrate and calcium stearate (generally 10%) is usually added as protective agent to make it stable.

Radiation effects

Various countries aim at surrounding residents of nuclear power plants to provide or reserves iodine tablets, the main ingredient is potassium iodide, when nuclear power plant occurs disaster and radiation leaks, the surrounding residents should take iodine tablets, iodine can saturate the thyroid gland and reduce absorption of radioactive iodine-131. When suffers the free iodine radiation exposure, within four hours can take effect, but it can not prevent ionizing radiation of iodine-131 exceptant and isotope. Improper use may cause hyperthyroidism symptoms without instructions for most people.

Solubility in water

Grams which dissolves in per 100 ml of water at different temperatures (℃):
128g/0 ℃; 136g/10 ℃; 144g/20 ℃; 153g/30 ℃; 162g/40 ℃; 168g/50 ℃
176g/60 ℃; 192g/80 ℃; 198g/90 ℃; 206g/100 ℃

Preparation

Potassium iodide is made by absorption of iodine in potassium hydroxide:
POTASSIUM IODIDE 7613I2 + 6KOH → 5KI + KIO3 + 3H2O
Most potassium iodate, KIO3 , is separated from the product mixture by crystallization and filtration. Remaining iodates are removed by evaporation of the solution and other processes, such as carbon reduction or thermal decompostion at 600ºC to iodide:
2KIO3 → 2KI + 3O2
Another method of preparation that does not involve the formation of iodate is by treating iron turnings with iodine solution. The product, ferrosoferric iodide, Fe3I8•16H2O, is boiled with 15 wt% potassium carbonate solution: Fe3I8•16H2O + 4K2CO3 → 8 KI + 4CO2 + Fe3O4 + 16H2O
A similar method is used to prepare potassium bromide, discussed earlier (see Potassium Bromide.)
Potassium iodide can be prepared by reacting hydriodic acid with potassium bicarbonate:
HI + KHCO3 → KI + CO2 + H2O
It is purified by melting in dry hydrogen.
Potassium iodide also may be obtained by various electrolytic processes.

Identification test

10% of the sample liquid potassium test (IT-27) and iodide test (IT-18), it is positive.

Toxicity

Approx LD i.v. in rats: 285 mg/kg (Hildebrandt)

Chemical Properties

White crystals, granules, or powder; strong, bitter, saline taste. Soluble in water, alcohol, acetone, and glyc- erol.

Occurrence

Potassium iodide is found in seaweed. Some important applications of this compound involve its use in pharmaceuticals and as a source of iodine in food,especially in animal and poultry feed. Potassium iodide is added to table salt to provide iodine in human food.
Another major use is in making photographic emulsions. In analytical chemistry, potassium iodide is used in iodometric titration with starch indicator to analyze dissolved oxygen, dissolved chlorine, sulfide, and other analytes in water.

Uses

Potassium iodide is a white crystal, granule or powder made by the reaction of iodine with hot potassium hydroxide solution followed by crystallization. It is very soluble in water, alcohol, and acetone. Potassium iodide was first used as the primary halide in Talbot’s calotype process, then in the albumen on glass process followed by the wet collodion process. It was also used as a secondary halide in silver bromide gelatin emulsions.

Uses

Potassium Iodide is a source of iodine and a nutrient and dietary supplement. it exists as crystals or powder and has a solubility of 1 g in 0.7 ml of water at 25°c. it is included in table salt for the preven- tion of goiter.Potassium Iodide is used primarily used in the treatment of radiation poisoning due to environmental contamination by iodine-131.

Uses

manufacture of photographic emulsions; in animal and poultry feeds to the extent of 10-30 parts per million; in table salt as a source of iodine and in some drinking water; also In animal chemistry. In medicine,potassium iodide is used to regulate the thyroid gland.

Definition

potassium iodide: A white crystallinesolid, KI, with a strong bittertaste, soluble in water, ethanol, andacetone; cubic; r.d. 3.13; m.p. 681°C;b.p. 1330°C. It may be prepared bythe reaction of iodine with hot potassiumhydroxide solution followed by separation from the iodate (which isalso formed) by fractional crystallization.In solution it has the interestingproperty of dissolving iodine to formthe triiodide ion I₃^-, which is brown.Potassium iodide is widely used as ananalytical reagent, in photography,and also as an additive to table salt toprevent goitre and other disordersdue to iodine deficiency.

Definition

A compound that contains pentavalent iodine, which is usually ionically bound to electropositive atoms.

brand name

Iosat (Anbex); Thyro-Block (Medpointe); Thyrosafe (R R Registrations); Thyroshield (Fleming).

General Description

Air & Water Reactions

Water soluble.

Reactivity Profile

Bromine trifluoride rapidly attacks the following salts: barium chloride, cadmium chloride, calcium chloride, cesium chloride, lithium chloride, silver chloride, rubidium chloride, potassium bromide, potassium chloride, Potassium iodide, rhodium tetrabromide, sodium bromide, sodium chloride, and sodium iodide [Mellor 2, Supp. 1:164, 165. 1956].

Health Hazard

May irritate eyes or open cuts.

Clinical Use

Potassium iodide is used to treat the cutaneous lymphatic form of sporotrichosis, although newer agents are also effective in this disorder and may be better tolerated tolerated. The drug is also used for erythema nodosum and nodular vasculitis.

Safety Profile

Poison by intravenous route. Moderately toxic by ingestion and intraperitoneal routes. Human teratogenic effects by ingestion: developmental abnormalities of the endocrine system. Experimental teratogenic and reproductive effects. Mutation data reported. Explosive reaction with charcoal + ozone, trifluoroacetyl hypofluorite, fluorine perchlorate. Violent reaction or ignition on contact with dazonium salts, diisopropyl peroxydicarbonate, bromine pentafluoride, chlorine trifluoride. Incompatible with oxidants, BrF3, FClO, metaltic salts, calomel. When heated to decomposition it emits very toxic fumes of K2O and I-. See also IODIDES.

Purification Methods

Crystallise it from distilled water (0.5mL/g) by filtering the near-boiling solution and cooling. To minimise oxidation to iodine, the process can be carried out under N2 and the salt is dried under a vacuum over P2O5 at 70-100o. Before drying, the crystals can be washed with EtOH or with acetone followed by pet ether. It has also been recrystallised from water/ethanol. After 2 recrystallisations, ACS/USP grade had Li and Sb at <0.02 and <0.01 ppm respectively. [Lingane & Kolthoff Inorg Synth I 163 1939.]