Potassium cyanide

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Potassium cyanide
Names
IUPAC name
Potassium cyanide
Properties
KCN
Molar mass 65.12 g/mol
Appearance White solid
Odor Faint almond-like
Density 1.52 g/cm3
Melting point 634.5 °C (1,174.1 °F; 907.6 K)
Boiling point 1,625 °C (2,957 °F; 1,898 K)
71.6 g/100 ml (25 °C)
100 g/100 mL (100 °C)
Solubility Soluble in glycerol
Solubility in ethanol 0.57 g/100 ml
Solubility in formamide 14.6 g/100 ml
Solubility in hydroxylamine 41 g/100 ml
Solubility in methanol 4.91 g/100 ml (20 °C)
Acidity (pKa) 11.0
Thermochemistry
127.8 J·K−1·mol−1
−131.5 kJ/mol
Hazards
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
5 mg/kg (oral, rabbit)
10 mg/kg (oral, rat)
5 mg/kg (oral, rat)
8.5 mg/kg (oral, mouse)
Related compounds
Related compounds
Sodium cyanide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Potassium cyanide is a compound with the formula KCN.

Properties

Chemical

Potassium cyanide can be oxidized to potassium cyanate.

Physical

Potassium cyanide is a white solid soluble in water.

Availability

Chemical suppliers may sell potassium cyanide, however, due to its high toxicity it's almost impossible to get hold of.

Preparation

There are several ways to produce potassium cyanide.

One route involves melting urea with potassium hydroxide. This gives potassium cyanate. Crush the resulting solid and grind it. Mix it with a reducing agent, such as carbon or magnesium to make a thermite-like mixture. Ignite it to reduce the potassium cyanate to potassium cyanide and magnesium or carbon oxides. This route gives impure potassium cyanide which needs to be purified.

A different route involves treating formamide with potassium hydroxide.

Decomposition of potassium ferrocyanide also gives potassium cyanide.

Another more dangerous route involves the acidification of Prussian blue to give hydrogen cyanide which is bubbled to a cooled solution of potassium hydroxide. This gives crude potassium cyanide which can be purified by recrystallization.

Projects

  • Make organic nitriles
  • Extract and dissolve gold, silver metal

Handling

Safety

Potassium cyanide is highly toxic. Ingestion can lead to death. Lethal dose for an average weight person is considered to be between 200–300 mg.

Storage

Potassium cyanide should be stored in closed bottles, away from any acids, in a locked cabinet with a clear hazard label on the storage bottle.

Disposal

Can be destroyed by oxidizing it with excess bleach or hydrogen peroxide to potassium cyanate.

References

Relevant Sciencemadness threads