Hydrocyanic acid . Hydrogen cyanide [HC≡N (g)] or hydrocyanic acid [HC≡N (ac)], prussic acid, methanonitrile or formonitrile is a chemical compound whose formula is: HCN. The dissolution of hydrogen cyanide in water is called hydrocyanic acid. The cyanide pure hydrogen is a colorless liquid, highly poisonous and highly volatile, boiling at 26 ° C. It has a slight bitter almond odor, which some people cannot detect due to a genetic trait. Hydrogen cyanide is slightly acidic. Its salts are known as cyanides.
Summary
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- 1 History of hydrocyanic acid
- 2 Main physical properties
- 1 Physical properties
- 3 Main methods of obtaining
- 4 Health risk
- 5 Source
Hydrocyanic acid history
Hydrocyanic acid was first isolated from the blue dye (Prussian blue), this dye was known as early as 1704 but its molecular structure was completely unknown. Today it is known as a coordination polymer with a complex structure and an empirical formula derived from the hydration of ferrocyanide. In 1752, the French chemist Pierre Macquer took an important step by showing that Prussian blue could be converted into an iron oxide plus a volatile compound that could be used as a dye restorative.
The new component was known as hydrogen cyanide. The following discoveries after Macquer were the isolation and characterization of hydrocyanic acid in its purest form since Prussian blue in 1783 by the Swedish chemist Carl Wilhelm Scheele, and during that time it was eventually given the German name: ( in German) Blausäure (literally “blue acid”) due to its acidic nature in water and its derivation from Prussian blue. In English it became popularly known as prussic acid.
In 1787 the French chemist Claude Louis Berthollet demonstrated that prussic acid did not contain oxygen, an important contribution to acid theory, by promulgating that acids come from oxygen. (The word oxygen derives from the classical Greek and means “the acid-forming” and is used in languages such as German as a semantic trace such as: Sauerstoff). In 1815 Joseph Louis Gay-Lussac deduced the chemical formula for acid. The cyanidric radical: ‘cyan’ comes from the classical Greek which means blue, due to its origin from Prussian blue.
Name (IUPAC) Hydrogen cyanide Other names Hydrogen cyanide
- prussic acid
- methanonitrile
- Blue acid
- Cyclone
- Cyan
- Anni methacholine
- Formonitrile
- Chemical formula:HCN
- Appearance:Colorless liquid
Main physical properties
Physical properties
- Molecular weight:0 amu
- Melting point:260 K (-13 ° C)
- Boiling point:299 K (26 ° C)
- Density:7 × 10³ kg / m³
- Solubility:Very soluble
Main methods of obtaining
Hydrogen cyanide is produced in large quantities worldwide by the chemical industry. It can be produced by causing the reaction between a cyanide and a strong acid, or directly from ammonia and carbon monoxide.
The most used processes:
The most important process is the Andrussov oxidation, invented by Leonid Andrussow at IG Farben in which methane and ammonia react in the presence of oxygen around 1200 ° C on a platinum catalyst: 2 CH4 + 2 NH3 + 3 O2 → 2 HCN + 6 H2O The energy required for the reaction is provided by the partial oxidation of methane and ammonia.
Of lesser importance is the Degussa process (BMA process) in which oxygen is not added and energy must be transferred indirectly through the reactor wall: CH4 + NH3 → HCN + 3H2 This reaction is similar to that of steam reforming , in which methane reacts with water to give carbon monoxide and hydrogen. In the Shawinigan process, ammonia and natural gas carry more coke. As practiced at BASF, the formamide is heated and is divided into hydrogen cyanide and water: CH (O) NH2 → HCN + H2O
In the laboratory, small amounts of HCN are produced by adding acids over cyanide salts of the alkali metals: H + + NaCN → HCN + Na +
This reaction can lead to accidental poisoning because the acid converts the cyanide salt into gaseous HCN. Utilization.
HCN is the precursor to sodium cyanide and potassium cyanide, which are mainly used in mining. Through the intermediation of cyanohydrins, a variety of useful organic compounds are prepared from HCN including methyl methacrylate monomer, acetone, aminoacidomethionine, through Strecker synthesis, and chelating agents EDTA and NTA. Through the hydrocyanation process, HCN is added to butadiene to give adiponitrile, a precursor to Nylon 66. It is used in dyes, explosives, plastics production.
Health risk
A concentration of 300 parts per million in the air is enough to kill a human in a matter of minutes. Its toxicity is due to the CN- cyanide ion, which inhibits cellular respiration. Its poisoning capacity is superior to that of CO in fires and allows to immobilize a victim in a short period of time, this effect must be taken into account by firefighters. It is usually produced by the combustion of synthetic products such as clothes, carpets, rugs, etc. its intake is usually due to inhalation.
Hydrocyanic acid or prussic acid is a toxic cyanide gas that is among the most potent and fastest-acting poisons. It was used in Nazi death camps, and in the United States it is used in executions in gas chambers
