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Element Index
Hafnium
Holmium
Hydrogen
Nitrogen
Chemical's truth
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Combinatorial chemistry is the study of techniques capable of rapidly synthesizing and generating millions of related compounds. |
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Hydrogen chloride
CAS no: 7647-01-0 Formula: HCl Molecular weight: 36.461
Physical Data
Appearance: Colorless gas, corrosive, nonflammable with pungent odor.
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Melting point: -114.17°C
Boiling point: -85.0°C
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Density: 1.490 g/L
Solubility: 442 vol. per unit vol. H2O (20°C)
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Thermodynamic Data (gas phase)
Enthalpy of formation: -92.3 kJ/mol
Gibbs energy of formation: -95.3 kJ/mol
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Entropy: 186.9 J/mol K
Heat capacity: 29.1 J/mol K
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Production and preparation
It is mostly manufacture from the reaction of sodium chloride with sulfuric acid (salt-cake method), a reaction discovered by Johann R Glauber (1604-1668),
a German-Dutch chemist.
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High-purity hydrogen chloride can be obtained by burning hydrogen and chlorine and as byproducts of chlorinated hydrocarbons.
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Behavior and Chemical Properties
Hydrogen chloride is extremely soluble in water, giving strong hydrochloric acid. Concentrated acid contains 28-35% by weight of HCl which appears as a fuming,
yellowish solution. The compound is extensively dissociated and the hydrogen ions stabilized by water to form hydronium ion ([H3O]+).
Completely dry hydrogen chloride is usually unreactive, but reacts with most metals and their oxides, carbonates etc in the presence of moisture.
When both reagent bottles contain concentrated hydrochloric acid and ammonia solutions are brought near to each other, white fumes of ammonium chloride are formed
near to the mouth of the opened bottles.
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Hydrochloric acid is a strong acid which attacks many metals to release hydrogen gas and with basic oxides and hydroxides to give water. For example, the reaction between zinc oxide
and hydrochloric acid produces zinc chloride (a salt) and water (neutralization reaction):
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History and Uses
The use of hydrogen chloride is usually in the form of solution. Liquidfied anhydrous hydrogen chloride is expensive to handle and the use of the chemical in this form is limited. The gas is used to manufacture anhydrous chemicals such as ammonium chloride and metal chlorides.
It is one of the important chlorinating agent in the manufacture of chloride compounds, such as vinyl chloride, alkyl chlorides etc. It is used in the industrial processing of metals and refining certain ores such as productions of tin and tantalum, which involve
reactions characteristics of complex chloride ions.
Albeit its toxicity, hydrochloric acid is present, in small amount, in the digestive juices of the human stomach. It provides acidic medium in aiding enzymic process of digestion.
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Hazard, Storage and Handling
Concentrated hydrochloric acid release hydrogen chloride gas (fumes). Avoid contact with water and store away from incompatible substances such as alkalis and most metals.
Both solution and gas are toxic and corrosive. Very harmful by inhalation, ingestion and through skin contact can cause serious burns and inflammation of the skin. Exposure to 0.1% by volume of the gas may cause death in a
few minutes. ID50 for mouse (intraperitoneal) is 40 mg/kg.
Safety googles and protective clothing must be worn and ensure effective ventilation when working with the substance.
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(Last update: January 2003) |
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