Potassium cyanide

Potassium cyanide

Names
IUPAC name Potassium cyanide
Properties
Chemical formula	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)
Solubility in water	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
Std molar entropy (So298)	127.8 J·K−1·mol−1
Std enthalpy of formation (ΔfHo298)	−131.5 kJ/mol
Hazards
Safety data sheet	Sigma-Aldrich
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (Median dose)	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

• Purer KCN
• Test Potassium Cyanide