Hydrochloric acid

Features of Hydrochloric acid

Hydrochloric acid, HCI, is a toxic and corrosive gas.

Physical and chemical properties

Physical state: Liquefied gas
Molecular weight: 36,5 g/mol
Smell: Pungent
Appearance/color: colorless


Hydrochloric acid is used:

  • in the chemical industry, to produce a wide variety of chlorinated organic compounds (methyl and ethyl chloride, benzene chlorides, etc.);
  • to produce chlorinated metals (e.g. aluminum or silicon chloride);
  • in hydro-metallurgical processes, to increase the separation coefficient of minerals;
  • in hot-dip galvanizing processes;
  • in calibration mixtures for environmental monitoring;
  • in the semiconductor fabrication cycle, for native oxide etching prior to epitaxial deposition, for cleaning in the reactors for chemical vapor deposition and moisture sequester phase in the oxides obtained by CVD (chemical vapor deposition);
  • in excimer lasers, combined with Xenon.


Stability and reactivity

It reacts with the major part of metals in the presence of humidity releasing hydrogen, an extremely flammable gas.
Combined with water, it causes rapid corrosion of some metals.
It reacts with water to form corrosive acids.
It can reacts violently with alkali.