Potassium iodide

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  Potassium iodide   
Names: potassium iodide

Formula: KI
SMILES: [K+].[I-]
Molar mass: 165.998 g/mol
Density: 3.123 g/cm3
Crystal system: cubic
a=7.06 Å
7.0600 Å
0.7060 nm
, b=7.06 Å
7.0600 Å
0.7060 nm
, c=7.06 Å
7.0600 Å
0.7060 nm
α=90°
90°  
, β=90°
90°  
, γ=90°
90°  

Forms:
https://media.crystalls.info/w/uploads/media/Tetragonal_flat_prism.json
https://media.crystalls.info/w/uploads/media/Tetragonal_prism.json

Color: colorless
Melting point: 681 °C
954.15 K
1,257.8 °F
1,717.47 °R

Boiling point: 1330 °C
1,603.15 K
2,426 °F
2,885.67 °R

Refractive index: 1.667
Magnetic properties: diamagnetic
Radiation properties: slightly radioactive
Stability: slightly hygroscopic
Hardness: strong
Toxicity: slightly toxic

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% 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% 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

Store in its original form or under several layers of varnish at average humidity and room temperature. Do not store in matchboxes or cotton wool and do not heat.

Solubility

Temperatureгр/100,00 гр waterгр/100,00 гр ethanolгр/100,00 гр ethanol 40%гр/100,00 гр methanolгр/100,00 гр acetoneгр/100,00 гр diethyl etherгр/100,00 гр glycerolгр/100,00 гр DMSOгр/100,00 гр pyridineгр/100,00 гр furfuralгр/100,00 гр ethylene glycolгр/100,00 гр formic acid 95%гр/100,00 гр propanolгр/100,00 гр isobutanolгр/100,00 гр 1-butanolгр/100,00 гр 2-butanolгр/100,00 гр ammoniaгр/100,00 гр ethylenediamineгр/100,00 гр hydroxylamineгр/100,00 гр acetamideгр/100,00 гр dimethylformamideгр/100,00 гр nitromethaneгр/100,00 гр acetonitrileгр/100,00 гр benzonitrileгр/100,00 гр propionitrileгр/100,00 гр amyl alcoholгр/100,00 гр benzaldehydeгр/100,00 гр salicylic aldehyde
0°C
273.15 K
32 °F
491.67 °R
127.3
127.3 g/100g
56.005 %
1.5
1.5 g/100g
1.478 %
2.31
2.31 g/100g
2.258 %
184.2
184.2 g/100g
64.814 %
0.316
0.316 g/100g
0.315 %
2.31
2.31 g/100g
2.258 %
0.0429
0.0429 g/100g
0.0429 %
1.105
1.105 g/100g
1.093 %
10°C
283.15 K
50 °F
509.67 °R
135.8
135.8 g/100g
57.591 %
~1.63
1.63 g/100g
1.604 %
13.6
13.6 g/100g
11.972 %
15°C
288.15 K
59 °F
518.67 °R
~140
140 g/100g
58.333 %
~1.69
1.69 g/100g
1.662 %
~14.4
14.4 g/100g
12.587 %
20°C
293.15 K
68 °F
527.67 °R
144.5
144.5 g/100g
59.1 %
1.75
1.75 g/100g
1.72 %
15.1
15.1 g/100g
13.119 %
50
50 g/100g
33.333 %
16
16 g/100g
13.793 %
0.5
0.5 g/100g
0.498 %
50
50 g/100g
33.333 %
38.2
38.2 g/100g
27.641 %
110
110 g/100g
52.381 %
25°C
298.15 K
77 °F
536.67 °R
148.6
148.6 g/100g
59.775 %
1.88
1.88 g/100g
1.845 %
4.82
4.82 g/100g
4.598 %
~15.7
15.7 g/100g
13.57 %
2.04
2.04 g/100g
1.999 %
39.66
39.66 g/100g
28.398 %
5.2
5.2 g/100g
4.943 %
36.05
36.05 g/100g
26.498 %
0.43
0.43 g/100g
0.428 %
0.0955
0.0955 g/100g
0.0954 %
0.201
0.201 g/100g
0.201 %
0.0582
0.0582 g/100g
0.0582 %
74.9
74.9 g/100g
42.824 %
25
25 g/100g
20 %
0.307
0.307 g/100g
0.306 %
0.0506
0.0506 g/100g
0.0506 %
0.0404
0.0404 g/100g
0.0404 %
0.098
0.098 g/100g
0.0979 %
0.329
0.329 g/100g
0.328 %
0.485
0.485 g/100g
0.483 %
30°C
303.15 K
86 °F
545.67 °R
152.5
152.5 g/100g
60.396 %
16.3
16.3 g/100g
14.015 %
40°C
313.15 K
104 °F
563.67 °R
159.7
159.7 g/100g
61.494 %
18.1
18.1 g/100g
15.326 %
50°C
323.15 K
122 °F
581.67 °R
~168
168 g/100g
62.687 %
18.9
18.9 g/100g
15.896 %
60°C
333.15 K
140 °F
599.67 °R
175.5
175.5 g/100g
63.702 %
~20.1
20.1 g/100g
16.736 %
70°C
343.15 K
158 °F
617.67 °R
~183
183 g/100g
64.664 %
~21.3
21.3 g/100g
17.56 %
21.65
21.65 g/100g
17.797 %
80°C
353.15 K
176 °F
635.67 °R
190.7
190.7 g/100g
65.6 %
~22.5
22.5 g/100g
18.367 %
90°C
363.15 K
194 °F
653.67 °R
198
198 g/100g
66.443 %
~23.8
23.8 g/100g
19.225 %
100°C
373.15 K
212 °F
671.67 °R
206.7
206.7 g/100g
67.395 %
25
25 g/100g
20 %
Soluble in ethyl acetate. Slightly soluble in dimethylamine. Insoluble in isopropanol and trimethylamine.

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