Potassium iodide

Potassium iodide ;
Names:	potassium iodide; potassium jodide;
Formula:	KI;
Molar mass:	165.998 g/mol;
Density:	3.123 g/cm3;
Crystal system:	cubic; a=7.06 Å, b=7.06 Å, c=7.06 Åα=90°, β=90°, γ=90°;
Shapes:	https://en.crystalls.info/w/uploads/media/3/30/Tetragonal_flat_prism.json Tetragonal flat prism https://en.crystalls.info/w/uploads/media/a/af/Tetragonal_prism.json Tetragonal prism ;
Color:	colorless;
Melting point:	681 °C954.15 K <br />1,257.8 °F <br />1,717.47 °R <br />;
Boiling point:	1330 °C1,603.15 K <br />2,426 °F <br />2,885.67 °R <br />;
Refractive index:	1.667 ;
Magnetic properties:	diamagnetic;
Radiation properties:	slightly radioactive;
Stability:	slightly hygroscopic;
Hardness:	strong;
Toxicity:	non-toxic; LD50=2779mg/kg

Description

Inorganic compound, salt of alkaline metal potassium and inorganic hydroiodic acid. Doesn't form water hydrates.

Precursors

Reaction between iodine, potassium hydroxide and hydrogen peroxide

Chemical equation:

2KOH + I₂ + H₂O₂ = 2KI + 2H₂O + O₂↑

For preparation of 100.00g of potassium iodide а 33.80g of hydroxide, 341.51g of

3%3%
30%

peroxide and 76.45g of iodine is required.

Add to the flask with hydroxide solution hydrogen peroxide and then add small parts of iodine with stirring until oxide emission will stop. For purifying compound from hydroxide add large amount of cold ethanol, acetone or toluene to solution, salt will settle to the bottom in the form of fine crystals or powder. Filter precipitate and wash it with small amount of the same solvent, then filter the solution and use it for crystal growing.

Reaction between potassium hydroxide or carbonate фтв hydroiodic acid

Chemical equation:

KOH + HI = KI + H₂O

K₂CO₃ + 2HI = 2KI + H₂O + CO₂↑

For preparation of 100.00g of potassium iodide а 33.80g of hydroxide or 41.63g of carbonate and 135.18g of 57%57% hydrobromic acid is required.

Add acid to the flask, then add small parts of potassium compound with stirring until heating will stop (attention, the solution may boil!) or, if you use carbonate, until carbon dioxide emission will stop.

The problem is that hydroiodic acid is rarely occurs, so reaction is rarely used.

Influence of temperature

Dissolving is endothermic, solution cools much, so use hot water or using heat.
Rapid cooling causes prismatic crystals growth.

Influence of impurities

Excess of iodine causes reddening of solution, excess of potassium hydroxide causes slowing down crystal growth or finally stops it.

Notes

Reacts with humid air with forming iodine at the crystal surface, so crystals becomes more dark-colored.
Too big solubility in water is intervenes growing process, so using organic solvents should be preferred.

Storage conditions

Keep in its original form or under several layers of varnish at average humidity and room temperature. Do not keep crystals near heaters.

Solubility

TableGraph

Temperature	g/`100,00` g water	g/`100,00` g ethanol 40%	g/`100,00` g ethanol	g/`100,00` g methanol	g/`100,00` g acetone	g/`100,00` g diethyl ether	g/`100,00` g glycerol	g/`100,00` g DMSO	g/`100,00` g pyridine	g/`100,00` g furfural	g/`100,00` g ethylene glycol	g/`100,00` g formic acid 95%	g/`100,00` g propanol	g/`100,00` g isobutanol	g/`100,00` g 1-butanol	g/`100,00` g 2-butanol	g/`100,00` g ammonia	g/`100,00` g ethylenediamine	g/`100,00` g hydroxylamine	g/`100,00` g acetamide	g/`100,00` g dimethylformamide	g/`100,00` g nitromethane	g/`100,00` g acetonitrile	g/`100,00` g benzonitrile	g/`100,00` g propionitrile	g/`100,00` g amyl alcohol	g/`100,00` g benzaldehyde	g/`100,00` g salicylic aldehyde
0°C273.15 K <br />32 °F <br />491.67 °R <br />	`127.3`		`1.5`		`2.31`												`184.2`					`0.316`	`2.31`		`0.0429`			`1.105`
10°C283.15 K <br />50 °F <br />509.67 °R <br />	`135.8`		`~1.63`	`13.6`
15°C288.15 K <br />59 °F <br />518.67 °R <br />			`~1.69`
20°C293.15 K <br />68 °F <br />527.67 °R <br />	`144.5`		`1.75`	`15.1`		`50`		`16`	`0.5`		`50`	`38.2`							`110`
25°C298.15 K <br />77 °F <br />536.67 °R <br />	`148.6`	`4.82`	`1.88`		`2.04`		`39.66`			`5.2`	`36.05`		`0.43`	`0.0955`	`0.201`	`0.0582`		`74.9`			`25`	`0.307`		`0.0506`	`0.0404`	`0.098`	`0.329`	`0.485`
30°C303.15 K <br />86 °F <br />545.67 °R <br />	`152.5`			`16.3`
40°C313.15 K <br />104 °F <br />563.67 °R <br />	`159.7`			`18.1`
50°C323.15 K <br />122 °F <br />581.67 °R <br />				`18.9`
60°C333.15 K <br />140 °F <br />599.67 °R <br />	`175.5`
70°C343.15 K <br />158 °F <br />617.67 °R <br />																				`21.65`
80°C353.15 K <br />176 °F <br />635.67 °R <br />	`190.7`
90°C363.15 K <br />194 °F <br />653.67 °R <br />	`198`
100°C373.15 K <br />212 °F <br />671.67 °R <br />	`206.7`			`25`

Soluble in ethyl acetate. Slightly soluble in dimethylamine. Insoluble in isopropanol and trimethylamine.

Gallery

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Iodides
Salts	Germanium iodide (GeI₄) • Cadmium iodide (CdI₂) • Lead(II) iodide (PbI₂) • Potassium iodide (KI) • Sodium iodide (NaI) • Tin(II) iodide (SnI₂)
Complexes	Potassium tetraiodobismuthate (К[BiI₄]) • Potassium tetraiodomercurate(II) (K₂[HgI₄])

Potassium compounds
Salts	Potassium bromate (KBrO₃) • Potassium bromide (KBr) • Potassium chlorate (KClO₃) • Potassium chloride (KCl) • Potassium chromate (K₂CrO₄) • Potassium dihydrophosphate (KH₂PO₄) • Potassium dichromate (K₂Cr₂O₇) • Potassium iodide (KI) • Potassium hydrofluoride (KHF₂) • Potassium hydrophosphate (K₂HPO₄) • Potassium hydrophthalate (KC₈H₆O₄) • Potassium metavanadate (KVO₃) • Potassium nitrate (KNO₃) • Potassium sulfate (K₂SO₄) • Potassium thiocyanate (KNCS)
Double salts	Aluminum-potassium sulfate (KAl(SO₄)₂) • Antimony(III)-potassium tartrate (K₂Sb₂(C₄H₂O₆)₂) • Chromium(III)-potassium sulfate (KCr(SO₄)₂) • Cobalt(II)-potassium sulfate (K₂Co(SO₄)₂) • Copper(II)-potassium sulfate (K₂Cu(SO₄)₂) • Indium(III)-potassium sulfate (KIn(SO₄)₂) • Iron(II)-potassium sulfate (K₂Fe(SO₄)₂) • Iron(III)-potassium sulfate (KFe(SO₄)₂) • Lithium-potassium sulfate (KLiSO₄) • Magnesium-potassium sulfate (K₂Mg(SO₄)₂) • Magnesium-potassium sulfate-chromate (K₂CrO₄ · MgSO₄) • Manganese(II)-potassium sulfate (K₂Mn(SO₄)₂) • Nickel-potassium sulfate (K₂Ni(SO₄)₂) • Potassium-sodium tartrate (KNaC₄H₄O₆) • Vanadium(III)-ammonium sulfate (NH₄V(SO₄)₂) • Zinc-potassium sulfate (K₂Zn(SO₄)₂)
Complexes	Potassium dioxalatocuprate(II) (K₂[Cu(C₂O₄)₂]) • Potassium hexanitrocobaltate(III) (K₃[Co(NO₂)₆]) • Potassium hexachlororhodiate(III) (K₃[RhCl₆]) • Potassium hexacyanocobaltate(III) (K₃[Co(CN)₆]) • Potassium hexacyanoferrate(II) (K₄[Fe(CN)₆]) • Tripotassium-sodium hexacyanoferrate(II) (K₃Na[Fe(CN)₆]) • Potassium hexacyanoferrate(III) (K₃[Fe(CN)₆]) • Potassium hexacyanochromate(III) (K₃[Co(CN)₆]) • Potassium tetraiodobismuthate (К[BiI₄]) • Potassium tetraiodomercurate(II) (K₂[HgI₄]) • Potassium trioxalatoaluminate (K₃[Al(C₂O₄)₃]) • Potassium trioxalatocobaltate(III) (K₃[Co(C₂O₄)₃]) Potassium trioxalatoferrate(III) (K₃[Fe(C₂O₄)₃]) • Potassium-sodium trioxalatoferrate(III) (K₅Na[Fe(C₂O₄)₃]₂) • Dipotassium-sodium trioxalatoferrate(III) (K₂Na[Fe(C₂O₄)₃]) • Potassium trioxalatochromate(III) (K₃[Cr(C₂O₄)₃])

Potassium iodide
Names:	potassium iodide potassium jodide
Formula:	KI
Molar mass:	165.998 g/mol
Density:	3.123 g/cm³
Crystal system:	cubic a=7.06 Å, b=7.06 Å, c=7.06 Åα=90°, β=90°, γ=90°
Shapes:	Tetragonal flat prism Tetragonal prism
Color:	colorless
Melting point:	681 °C954.15 K <br />1,257.8 °F <br />1,717.47 °R <br />
Boiling point:	1330 °C1,603.15 K <br />2,426 °F <br />2,885.67 °R <br />
Refractive index:	1.667
Magnetic properties:	diamagnetic
Radiation properties:	slightly radioactive
Stability:	slightly hygroscopic
Hardness:	strong
Toxicity:	non-toxic LD₅₀=2779mg/kg