Hydrochloric acid


It is used in the manufacture of phosphoric acid, chlorine dioxide, ammonium chloride, fertilisers, dyes, and artificial silk and pigments for paints. It is used as a refining ore in the production of tin and tantalum, as a lab reagent, and as a metal treating agent. It is used to remove scale and dust from boilers and heat exchange equipment, to clean membranes in desalination plants, to increase oil well output, to prepare synthetic rubber products by treating isoprene, and to clean and prepare other metals for coatings. It is used in the neutralisation of waste streams, the recovery of zinc from galvanised iron scrap, the production of chloride chemicals, the production of vinyl chloride from acetylene and alkyl chlorides from olefins, the manufacture of sodium glutamate and gelatine, the conversion of cornstarch to syrup, sugar refining, electroplating, soap refining, leather tanning, and the photographic, textile, brewing, and rubber industries. It is used to maintain pH balance in swimming pools, spas, etc. It is also used as a bactericide, a fungicide, and a virucide to disinfect bathrooms, kitchens and food preparation areas, and other areas in commercial and industrial buildings, in hospitals, in nursing homes, and in and around household dwellings. It is used in food processing as a starch modifier.

Substance details

Substance name: Hydrochloric acid

CASR number: 7647-01-0

Molecular formula: HCl

Synonyms: muriatic acid; chlorohydric acid; hydrochloride; spirits of salts; hydrogen chloride (acid); hydrogen chloride; hydrogen chloride gas only

Physical properties

Hydrochloric acid is a solution of hydrogen chloride in water. Hydrogen chloride occurs as either a colourless liquid with a an irritating, pungent odour, or a colourless to slightly yellow gas which can be shipped as a liquefied compressed gas; highly soluble in water.

Melting Point: -114.24°C

Boiling Point: -85.06°C

Specific Gravity: 1.2

Vapour Density: 1.268

1 ppm = 1.49 mg/m3

Chemical properties

Hydrochloric acid is one of the most corrosive of the non-oxidising acids in contact with copper alloys, and is handled in dilute solutions. Contact with metals produces hydrogen gas, which creates the chance of an explosion. It produces poisonous gas, including chlorine, in a fire. It is soluble in benzene, alcohol, and ether; it is insoluble in hydrocarbons, and incompatible or reactive with metals, hydroxides, amines, and alkalis. Hydrochloric acid's fumes have an acid, penetrating odour. Aqueous solutions of hydrochloric acid attack and corrode nearly all metals, except mercury, silver, gold, platinum, tantalum, and certain alloys. It may be coloured yellow by traces of iron, chlorine, and organic matter.

Non-flammable gas.

Further information

The National Pollutant Inventory (NPI) holds data for all sources of hydrochloric acid emissions in Australia.


Exposure to concentrated hydrochloric acid can cause circulatory collapse, which may lead to death; it can also cause death by asphyxia due to glottic oedema. Less concentrated solutions, can also cause conjunctivitis and corneal burns, inflammation and ulceration of the respiratory tract, dermatitis, skin burns, rhinitis, laryngitis, tracheitis, bronchitis, pulmonary oedema, dental erosion, hoarseness, a feeling of suffocation, nausea, vomiting, abdominal pain, diarrhoea, dehydration, convulsions, oliguria, hypotension, chills, shock, lethargy, stupor, permanent visual damage, cough, and choking. Ingestion or skin contact with hydrochloric acid can cause corrosion of mucous membranes of the mouth, throat, and oesophagus, with immediate pain and dysphagia; it can also cause gastric haemorrhage and intense thirst.

Entering the body

Probable routes of human exposure to hydrochloric acid are skin contact and inhalation of hydrogen chloride gas.


Probable routes of human exposure to hydrochloric acid are inhalation and skin contact during any of the consumer uses of the chemical outlined above.

Health guidelines

Worksafe Australia has set the exposure standard for hydrochloric acid (hydrogen chloride) to 5 ppm (7.5 milligram/m3 (TWA).

Note: For some rapidly acting substances and irritants, averaging of airborne concentration over an eight hour period is inappropriate. These substances may induce acute effects after relatively brief exposure to high concentrations and so the exposure standard for these substances represents a maximum or peak concentration to which workers may be exposed.

Irritant: concentration cut-off level: 1% weight/weight

Corrosive: concentration cut-off level: 5% weight/weight


Hydrochloric acid has a high acute toxic effect on all forms of life. There is no information on long term effects. It will also accelerate the dissolution of many minerals, such as the carbonates (including limestone) and all aluminosilicates (such as clays and many igneous rocks). It thus contributes to the decay of limestone buildings, other structures such as bridges, and art works. It also contributes to the processes that cause photochemical smog.

Entering the environment

Hydrogen chloride is carried in the air. If released to soil, it will usually quickly react with alkaline and other buffering components, if present. It can be mobile in soil, however, and may contaminate groundwater.

Where it ends up

Hydrogen chloride released into the atmosphere as a gas will undergo wet and dry deposition, and will be readily incorporated into cloud, rain, and fog water. It thus forms a component of acid rain. It also contributes to the processes that cause photochemical smog.

Environmental guidelines

No national guidelines.

Industry sources

Manufacturers of industrial inorganic chemicals; electric services companies; and manufacturers of guided missiles, space vehicles, and parts. Also, the combustion of fuels, refuse incineration, smelting of metal scrap, thermal decomposition of gases, and pyrolysis of wire insulation materials such as polyvinyl chloride, chlorinated acrylics, and retardant treated materials. It is also produced as a by-product in dehalogenation processes.

Diffuse sources, and industry sources included in diffuse emissions data

From its use to maintain pH balance in swimming pools, spas, etc; and its use as a bactericide, a fungicide, and a virucide to disinfect bathrooms, kitchens and food preparation areas, and other areas in commercial and industrial buildings, in hospitals, in nursing homes, and in and around household dwellings.

Natural sources

In the gases evolved from volcanoes and related geothermal activity. It does not occur free in nature but is a component of the minerals halite, sylvite, and carnallite, and as chloride ion in seawater.

Transport sources

Vehicle exhaust (from thermal decomposition processes).

Consumer products

Disinfectants, other polishing preparations and related products, toilet bowl cleaners, and stain-removers for brickwork and paving.

Sources used in preparing this information

  • ChemFinder WebServer Project (1995) (accessed, June, 1999)
  • Chemical Backgrounder (accessed, June, 1999)
  • Environmental Defense Fund - Summary, Uses, Consumer Products, Rank (industrial, by quantity) (accessed, June, 1999)
  • IPCS International Chemical Safety Card (accessed, June, 1999)
  • National Environment Protection Council (1998a), National Environment Protection Measure for the National Pollutant Inventory (accessed, June, 1999)
  • National Toxicology Program Health and Safety Information Sheet (accessed, June, 1999)
  • New Jersey Health and Safety (accessed, June, 1999)
  • Technical Advisory Panel (1999), Final Report to the National Environment Protection Council.
  • US EPA Health Effects Notebook for Hazardous Air Pollutants (accessed, June, 1999)
  • US EPA Integrated Risk Information System Report (accessed, June, 1999)
  • US EPA Toxic Release Inventory Fact Sheet (accessed, June, 1999)
  • WorkSafe Australia Exposure Standards Database: Hydrogen chloride (accessed, June, 1999)