What Is a Potassium Cyanide?
Potassium cyanide is an inorganic compound with the chemical formula KCN, also known as potassium cyanide or potassium cyanide. It is found as a colorless crystalline salt at room temperature and is soluble in water.
Although potassium cyanide has become synonymous with toxicity due to its strong toxicity, it is also an industrially important substance that is used in a wide range of fields, including organic synthesis, gold smelting, and electroplating.
Properties of Potassium Cyanide
Potassium cyanide is an ionic crystal composed of potassium and cyanide ions and is one of the typical alkali cyanide compounds. The carbon and nitrogen in the cyanide ion are linked by a triple bond.
Potassium cyanide is a white powdery crystal that is deliquescent, soluble in water, and strongly alkaline in aqueous solution. It is insoluble in organic solvents (methanol, ethanol, glycerin).
When it is tidied, it reacts with carbon dioxide in the air and releases hydrogen cyanide (HCN) while changing to potassium carbonate according to the following equation.
2 KCN + H2O + CO2 → K2CO3 + 2 HCN
Therefore, the product is odorless in the dry state, but in the air, it emits a characteristic almond odor due to hydrogen cyanide. Since the reaction is particularly likely to proceed under sunlight, the product should be stored away from sunlight to avoid exposure to air.
Production Process of Potassium Cyanide
Potassium cyanide is produced by treating hydrogen cyanide (HCN) with an aqueous solution of potassium hydroxide (KOH), followed by precipitation by evaporation of the solution in a vacuum.
HCN + KOH → KCN + H2O
Uses of Potassium Cyanide
Potassium cyanide is widely used in organic synthesis. Of particular importance is the reaction with alkyl halides to prepare nitriles (R-C≡N) according to the following formula:
R-X + KCN → R-CN + KX
Industrially, sodium cyanide (NaCN, sodium cyanide) is increasingly used in place of potassium cyanide.
It is also used as a photo-fixing agent. Potassium cyanide dissolves silver that is not insoluble in the developing solution. This makes the image clearer, more stable, and less sensitive to light. In modern times, sodium thiosulfate is increasingly used as a less toxic fixing agent.
It is also used as a smelting agent for gold, silver, and copper. Gold is leached from low-grade gold ores as a water-soluble salt according to the following formula:
4 Au (s) + 8 KCN (aq) + O2 (g) + 2 H2O (l) → 4 K[Au(CN)2] (aq) + 4 KOH (aq)
A similar process can also be used to leach as sodium gold cyanide NaAu(CN)2 using NaCN.
Potassium Cyanide Toxicity
When potassium cyanide enters the body orally, through the respiratory tract, or through the skin, cellular respiration is strongly inhibited and necrosis occurs. In the early stages of acute cyanide poisoning, the poisoned person’s complexion turns red because the tissues are unable to use oxygen from the blood. The brain is most affected, and death results from hypoxic encephalopathy. Symptoms of poisoning progress rapidly and will require immediate treatment. Symptoms usually appear within minutes of ingesting potassium cyanide. Respiratory distress, hypotension, loss of consciousness, and eventually brain death will occur.
The oral lethal dose of potassium cyanide is 200-300 mg for adults. The effects of sodium cyanide are similar to those of potassium cyanide.
If inhaled, fresh air should be immediately pumped into the lungs by artificial respiration. If ingested orally, the patient should vomit immediately (or be induced) and be artificially ventilated.