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Prudent Practices in the Laboratory: Handling and Disposal of Chemicals
LABORATORY CHEMICAL SAFETY SUMMARY: SODIUM CYANIDE AND POTASSIUM CYANIDE
NaCN: bp 1496 °C, mp 564 °C
KCN: bp 1625 °C, mp 634 °C
Soluble in water (NaCN: 37 g/100 mL; KCN: 41 g/100 mL)
The dry salts are odorless, but reaction with atmospheric moisture produces HCN, whose bitter almond odor is detectable at 1 to 5 ppm; however, 20 to 60% of the population are reported to be unable to detect the odor of HCN.
LD50 oral (rat)
6.4 mg/kg (NaCN)
5 mg/kg (KCN)
5 mg/kg (KCN)—skin
Highly toxic; exposure by eye or skin contact or ingestion can be rapidly fatal.
The acute toxicity of these metal cyanides is high. Ingestion of NaCN or KCN or exposure to the salts or their aqueous solutions by eye or skin contact can be fatal; exposure to as little as 50 to 150 mg can cause immediate collapse and death. Poisoning can occur by inhalation of mists of cyanide solutions and by inhalation of HCN produced by the reaction of metal cyanides with acids and with water. Symptoms of nonlethal exposure to cyanide include weakness, headache, dizziness, rapid breathing, nausea, and vomiting. These compounds are not regarded as having good warning properties.
Effects of chronic exposure to sodium cyanide or potassium cyanide are nonspecific and rare.
Flammability and Explosibility
Sodium cyanide and potassium cyanide are noncombustible solids. Reaction with acids liberates flammable HCN.
Reactivity and Incompatibility
Reaction with acid produces highly toxic and flammable hydrogen cyanide gas. Reaction with water can produce dangerous amounts of HCN in confined areas.
Storage and Handling
Sodium cyanide and potassium cyanide should be handled in the laboratory using the "basic prudent practices" described in Chapter 5.C, supplemented by the additional practices for work with compounds of high toxicity (Chapter 5.D). In particular, work with cyanides should be conducted in a fume hood to prevent exposure by inhalation,