Hydrogen chloride / HCl

Hydrogen chloride

Gas Identification

Other denomination

Hydrogen chloride

CAS Registry Number
SCBA type

Chemical properties

Molecular formula
Molecular mass
36,5 g/mol

Physical properties

Boiling point
-85 °C
Autoignition temperature
Gas/Vapour density
10,18 eV

Flammability limit


Threshold limit value

0 ppm • 0 mg/m³
5 ppm • 7,6 mg/m³

Hydrogen chloride : Description and use


Hydrogen chloride, like hydrochloric acid, is an important chemical in chemistry, industry and science. The name HCl sometimes wrongly refers to hydrochloric acid instead of pure hydrogen chloride. Chemists sometimes speak of gaseous or anhydrous hydrochloric acid to refer to hydrogen chloride.
It is a colourless gas, with an acrid odour which gives off fumes when it comes into contact with humid air.

Flammability and explosiveness: Anhydrous hydrochloric acid is a non-flammable and non-explosive compound. However, if exposed to humidity, it is corrosive to almost all metals and the reaction releases hydrogen, an extremely flammable and explosive gas.


Anhydrous hydrochloric acid and its aqueous solutions are used in many industries (pharmaceutical, phytopharmaceutical, food, chemical, electronics, metal, mining, oil, polymer, colouring agent, leather, textile, etc.). They are used in several reactions in organic chemistry and mineral chemistry.

Anhydrous hydrochloric acid is the base product in the manufacture of:

  • alkynyl chlorides
  • vinyl chlorides
  • trichlorosilane
  • chlorosulphonic acid
  • pharmaceutical products
  • fertiliser
  • phytopharmaceutical products

Hydrogen chloride in its aqueous solution (or aqueous solution hydrochloric acid):

  • for cleaning and pickling metals
  • for producing mineral chlorides
  • for extracting and purifying some ores
  • for recovering semi-precious metals from spent catalysts
  • for treating water (regenerating ion-exchange resins)
  • for manufacturing flocculants

Hydrogen chloride : Warnings and caution

GHS hazard statements

H280 - Contains gas under pressure; may explode if heated.
H331 - Toxic if inhaled.
H314 - Causes severe skin burns and eye damage.

GHS precautionary statements

P101 - If medical advice is needed, have product container or label at hand.
P280 - Wear protective gloves/protective clothing/eye protection/face protection.
P304+P340 - IF INHALED: Remove victim to fresh air and keep at rest in a position comfortable for breathing.
P305+P351+P338 - IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
P403+P233 - Store in a well-ventilated place. Keep container tightly closed.
P309+P311 - IF EXPOSED OR IF YOU FEEL UNWELL: call a POISON CENTRE or doctor/physician.

SGH04 : Gaz sous pression
SGH06 : Toxique
SGH05 : Corrosif