Hydrochloric acid
General
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|
|---|---|
| Name | Hydrogen chloride |
| Chemical formula | HCl |
| Appearance | Colourless gas |
Physical
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|
| Formula weight | 36.5 amu |
| Melting point | 203.15 K (-70 °C) |
| Boiling point | 326.15 K (53 °C) |
| Density | 1.2 ×103 kg/m3 (liquid) |
| Solubility | 70 g in 100g water |
Thermochemistry
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|
| ΔfH0gas | -92.31 kJ/mol |
| ΔfH0liquid | ? kJ/mol |
| ΔfH0solid | ? kJ/mol |
| S0gas, 1 bar | 186.9 J/mol·K |
| S0liquid, 1 bar | ? J/mol·K |
| S0solid | ? J/mol·K |
Safety
| |
| Ingestion | Toxic, can be fatal. |
| Inhalation | Fumes may be fatal. Do not give unprotected mouth-to-mouth resuscitation. |
| Skin | May cause severe burns. |
| Eyes | Extremely dangerous. |
| More info | Hazardous Chemical Database |
| SI units were used where possible. Unless otherwise stated, standard conditions were used. | |
The chemical compound hydrochloric acid is a highly acidic aqueous solution of hydrogen chloride (HCl). It is highly corrosive and should be handled only with appropriate precautions. Hydrochloric acid is a commonly used chemical reagent and is one of the strong acids that ionize completely in aqueous solution. Concentrated hydrochloric acid has a pH of less than 1.
Hydrochloric acid was discovered around 800 CE by Islamic alchemist Jabir Ibn Hayyam (Geber), by distilling common salt (NaCl) with sulphuric acid. It was known to European alchemists as spirit of salt or acidum salis. Gaseous HCl was called marine acid air. The old (pre-systematic) muriatic acid has the same origin (muriatic means "pertaining to brine or salt"). Hydrochloric acid is still sold under that name at industrial suppliers and hardware stores, for removing mortar stains and film from brickwork, masonry, and stonework.
Aqua regia is a mixture of hydrochloric and nitric acids.
Human digestive fluids consist of a mixture of hydrochloric acid and various enzymes which help break down proteins present in food.
Hydrochloric acid is now manufactured by combustion of chlorine gas in hydrogen to make hydrogen chloride gas followed by dissolution of the gas in water.
Hydrochloric acid is generally purchased in a concentrated form and is diluted in a fume cupboard (see making up solutions).