Potassium chloride

From Crystal growing


   Potassium chloride   
Names: potassium chloride
muriate of potash

Formula: KCl
SMILES: [Cl-].[K+]
Molar mass: 74.551 g/mol
Density: 1.988 g/cm3
Crystal system: cubic
a=6.29294 Å, b=6.29294 Å, c=6.29294 Åα=90°, β=90°, γ=90°

Color: colorless
Melting point: 776 °C1,049.15 K <br />1,428.8 °F <br />1,888.47 °R <br />
Boiling point: 1420 °C1,693.15 K <br />2,588 °F <br />3,047.67 °R <br />
Refractive index: 1.4902
Magnetic properties: diamagnetic
χ=-3.90 · 10-5cm³/mol
Radiation properties: slightly radioactive
Stability: stable
Hardness: strong
(2.5 on Moh's scale)
Toxicity: non-toxic


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


Occurs in nature as sylvite, sylvinite and carnallite minerals.

Where to buy

In fertilizers store (as "muriate of potash") and grocery store (as "salt with a reduced sodium content", mixture with sodium chloride in 1:1 ratio).


Reaction between potassium hydroxide or carbonate and hydrochloric acid

Chemical equation:

HCl + KOH = KCl + H2O
2HCl + K2CO3 = 2KCl + H2O + CO2

For preparation of 100.00g of potassium chloride а 75.26g of potassium hydroxide or 92.69g of carbonate and 128.70g of 38% hydrochloric acid is required.
Add acid to the flask, then add small parts of potassium compound with stirring until it will totally dissolve or, if you use carbonate, until carbon dioxide emission will stop. After reaction will stop, filter the solution and use it for crystal growing.

Recrystallization of "salt with a lower sodium content"

Add potassium and sodium chlorides mixture to the flask with boiling water until solution become saturated. Then filter out the solution and cool slowly. Excess of compound precipitates as a crystalline precipitate, most of impurities remain in the solution.

Separate this precipitate from the stock solution, and repeat this process for several times, use the same solution at each next step. Finally, the precipitated compound is used for crystal growing.

Influence of temperature

Temperature increase leads to changing crystals shape to long thin needles.

Influence of impurities

The technical compound impurities slightly affect a growth of crystals. For compound purifying filter the solution through a dense filter, and then recrystallize compound several times.

Excess of sodium chloride more than 40% of crysal mass leads to polycrystals forming. But, unlike sodium chloride, excess of urea does not affect to crystal shape at all.

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.


Temperatureгр/100,00 гр waterгр/100,00 гр ethanolгр/100,00 гр methanolгр/100,00 гр glycerolгр/100,00 гр furfuralгр/100,00 гр ethylene glycolгр/100,00 гр formic acid 95%гр/100,00 гр acetic acidгр/100,00 гр propanolгр/100,00 гр hydrazineгр/100,00 гр acetamideгр/100,00 гр dimethylformamideгр/100,00 гр N-methylformamideгр/100,00 гр formamide
0°C273.15 K <br />32 °F <br />491.67 °R <br />27.78
10°C283.15 K <br />50 °F <br />509.67 °R <br />30.91
15°C288.15 K <br />59 °F <br />518.67 °R <br />~32.50.0265
20°C293.15 K <br />68 °F <br />527.67 °R <br />34.03~0.0319.40.1959
25°C298.15 K <br />77 °F <br />536.67 °R <br />36.010.02880.546.70.0735.18~0.210.0042.450.052.16.2
30°C303.15 K <br />86 °F <br />545.67 °R <br />37.47~0.030.56~0.22
40°C313.15 K <br />104 °F <br />563.67 °R <br />40.310.03250.60~0.24
50°C323.15 K <br />122 °F <br />581.67 °R <br />43.050.0390.63~0.26
60°C333.15 K <br />140 °F <br />599.67 °R <br />45.64~0.040.670.285
70°C343.15 K <br />158 °F <br />617.67 °R <br />48.33~0.04~0.34
80°C353.15 K <br />176 °F <br />635.67 °R <br />50.850.049~0.40
90°C363.15 K <br />194 °F <br />653.67 °R <br />53.820.457
100°C373.15 K <br />212 °F <br />671.67 °R <br />56.37
Slightly soluble in pyridine. Insoluble in acetone, acetonitrile and amyl alcohol.