Key Properties and Industrial Applications of Sodium Cyanide
What Is Sodium Cyanide?
The chemical name of cyanide is Sodium Cyanide, and it is a highly toxic chemical. Sodium cyanide is known by many different names such as Cyanobrik, Cyanide of sodium, cyanide salt, or Cyanogen. It is basically a sodium salt as well as a one-carbon compound. It is an inorganic compound, as it is a typical chemical compound that does not have an established carbon and hydrogen bond. This sodium salt is white in colour and is soluble in water. It is one of the highly toxic salts as it has a high affinity (highly reactive) for metals. Sodium cyanide is also a moderately strong base, and when it is treated with an acid (such as sulfuric acid), it forms a highly toxic gas known as hydrogen cyanide.
Sodium Cyanide Formula
What is NaCN? Well, the formula of sodium cyanide is NaCN, where Na is sodium, and CN is cyanide.
Chemical Properties of Sodium Cyanide
When one treats sodium hydroxide with hydrogen cyanide, he gets sodium cyanide. All around the world, in the year 2006, almost 5 lakh tons of NaCN was produced. Therefore, we can assume the salt has vast application. After hydrolysis NaCN forms HCN (hydrogen cyanide acid) because this salt is derived from a very week acid. The HCN that is formed after hydrolysis smells like bitter almonds. Also, when NaCN is detoxified with Hydrogen Peroxide sodium cyanate and water is produced.
Sodium Cyanide Uses
Gold Mining- In the mining industry sodium cyanide has exorbitant uses. The main use of the cyanide is reflected in the process of extraction of gold as well as other precious metals from mines. Gold is highly reactive to cyanide, therefore, sodium cyanide is explicitly used in gold mining. When gold reacts with sodium cyanide in the presence of oxygen and water it produces sodium gold cyanide and sodium hydroxide.
Chemical Feedstock- Sodium cyanide helps in producing a number of commercially significant chemical compounds such as cyanogen chloride, many types of nitriles and also cyanuric chloride. Cyanide is a very strong nucleophile that donates a pair of electrons to form a chemical bond in relation to a reaction. In organic synthesis cyanide (nucleophile) helps in preparing nitriles. Nitriles are present in many chemicals, and it has vast usage in the pharmaceutical industry.
Other Uses- Sodium cyanide is a highly toxic chemical, it is therefore used for any illegal purposes such as killing by poisoning. Due to its poisonous nature, many use the chemical for killing insects and rodents. In many industries, it is used for cleaning metals. In the dye industry, the chemical is used to produce dyes. In many other sectors, the chemical is used to manufacture the electroplating solution. It is also used as an agricultural chemical and farmers use it as a pesticide to kill pests that damage the crop. This said the chemical can also be used for producing the hydrocyanic acid.
Other Properties of Sodium Cyanide
Sodium cyanide or NaCN is a toxic chemical. Its molecular weight is 46.006 g/mol. The density of this highly reactive chemical is 1.880 gram per cubic decimeter. The boiling point of the chemical is 21.15 degrees Celsius and its melting point is -9.3 degrees Celsius.
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Sodium Cyanide and the Health Hazards
Sodium cyanide or cyanogran is an extremely toxic chemical. For a human with an average weight of 70 kg, a dose less than 5 mg/kg is considered to be a safe amount of oral lethal dose. Now, any particular quantity above this limit can prove to be highly dangerous. Many a time, a portion of the chemical is found to be in the fruits or vegetables due to sprinkling of pesticides on them. Therefore such fruits and vegetables prove to be fatal. Government has therefore restricted the use of sodium cyanide as a pesticide for farms and agricultural lands. If a person inhales this chemical, absorbs through the skin or swallows it, it can be fatal and result in the death of a person. Direct contact with the chemical causes eyes and skin to burn. When the chemical reacts with humid air or water it releases flammable, corrosive, toxic gases.
FAQs on Sodium Cyanide: Formula, Properties, Uses & Health Effects
1. What is sodium cyanide and what is its chemical formula?
Sodium cyanide is an inorganic compound and a highly toxic salt of sodium and hydrocyanic acid. Its chemical formula is NaCN. It is typically a white, water-soluble solid. Due to its reaction with moisture in the air, it can sometimes have a faint, bitter almond-like odour, which is actually the smell of hydrogen cyanide gas being produced.
2. What are the main physical and chemical properties of sodium cyanide?
Sodium cyanide exhibits several key properties relevant to its use and handling in chemistry:
- Appearance: It exists as a white crystalline solid or powder.
- Solubility: It is very soluble in water but only sparingly soluble in alcohols like ethanol.
- Odour: While it can have a faint bitter almond smell, this is not a reliable indicator as not everyone can detect it and its absence does not mean danger.
- Melting Point: It has a high melting point of 563.7 °C (1,046.7 °F).
- Chemical Nature: As a salt derived from a strong base (NaOH) and a weak acid (HCN), its aqueous solution is distinctly alkaline (basic) because the cyanide ion hydrolyzes in water.
3. What are the primary industrial applications of sodium cyanide?
Despite its high toxicity, sodium cyanide is a crucial chemical in several major industries. Its most important uses include:
- Mining: It is essential for gold and silver extraction from low-grade ores. This process, known as cyanidation or the MacArthur-Forrest process, uses a dilute solution of NaCN to dissolve the precious metals.
- Electroplating: In this process, it is used in plating baths to help deposit thin, smooth, and adherent layers of metals like gold, silver, and zinc onto other surfaces.
- Chemical Synthesis: It serves as a key starting material (precursor) in the manufacturing of various organic and inorganic chemicals, including certain dyes, pharmaceuticals, and pesticides.
4. Why is an aqueous solution of sodium cyanide basic and not neutral?
An aqueous solution of sodium cyanide is basic due to a process called salt hydrolysis. Sodium cyanide (NaCN) is a salt formed from a strong base (Sodium Hydroxide, NaOH) and a weak acid (Hydrocyanic Acid, HCN). When NaCN dissolves in water, it dissociates into Na⁺ and CN⁻ ions. The cyanide ion (CN⁻) is the conjugate base of a weak acid, so it reacts with water molecules, accepting a proton to form HCN and leaving behind hydroxide ions (OH⁻). This increase in the concentration of OH⁻ ions makes the solution alkaline, or basic. The equilibrium reaction is: CN⁻ + H₂O ⇌ HCN + OH⁻.
5. How does sodium cyanide make it possible to extract gold from rock?
Sodium cyanide is used in a chemical process called cyanide leaching to extract gold from ore. Even though gold is chemically unreactive, it readily reacts with the cyanide ion (CN⁻) in the presence of an oxidizing agent, typically oxygen from the air. When finely crushed ore is mixed with a dilute sodium cyanide solution, the gold atoms are oxidized and dissolve to form a stable, water-soluble complex ion called dicyanoaurate(I), [Au(CN)₂]⁻. The simplified chemical equation for this reaction is: 4 Au + 8 NaCN + O₂ + 2 H₂O → 4 Na[Au(CN)₂] + 4 NaOH. The gold is then recovered from this solution by reacting it with a more reactive metal like zinc.
6. What are the health effects and mechanism of toxicity for sodium cyanide?
Sodium cyanide is a fast-acting and potent poison. Its toxicity stems from the cyanide ion (CN⁻). When it enters the body, it acts as a cellular asphyxiant by binding to the iron in cytochrome c oxidase, a crucial enzyme in the electron transport chain of cellular respiration. This binding prevents cells from using oxygen to produce ATP (energy). The primary health effects of exposure include:
- Dizziness, headache, and shortness of breath.
- Rapid heartbeat and nausea.
- Severe exposure can quickly cause convulsions, loss of consciousness, respiratory arrest, and death.
7. What is the fundamental difference between sodium cyanide (NaCN) and sodium chloride (NaCl)?
While both are white, crystalline sodium salts, they have critical differences:
- Origin and pH: NaCl is a salt of a strong acid (HCl) and a strong base (NaOH), making its solution neutral (pH ≈ 7). NaCN is a salt of a weak acid (HCN) and a strong base (NaOH), so its solution is basic (alkaline) due to hydrolysis.
- Toxicity: Sodium chloride (table salt) is essential for life. In stark contrast, sodium cyanide is a highly lethal poison that blocks cellular respiration.
- Reactivity: The chloride ion (Cl⁻) is generally unreactive and acts as a spectator ion in many reactions. The cyanide ion (CN⁻) is a highly reactive nucleophile and a strong ligand, which is why it can form stable complexes with metals like gold, a property central to its industrial use.
