Hydrochloric Acid is a Clear, Colorless, Highly Pungent solution of hydrogen chloride (HCl) in water.

It is a highly corrosive, strong mineral acid with many industrial uses.

It was historically called acidum salis, muriatic acid, and spirits of salt


Systematic Name
Hydrochloric acid

Other Names
Muriatic acid, Spirit of salt

Molecular formula
HCl in water (H2O)

Molar mass
36.46 g/mol (HCl)
Appearance Clear colorless to
light-yellow liquid

CAS number [7647-01-0]


Boiling point :

110 °C (383 K),
20.2% solution;
48 °C (321 K),
38% solution.

Density, phase 1.18 g/cm³,
37% solution.

Solubility in water
Fully miscible.

Melting point −
26 °C (247 K)
38% solution.

Acid dissociation
constant pKa −8.0

Viscosity 1.9 mPa•s at 25 °C,
31.5% solution


Chemical Properties and Reactions :

Hydrogen chloride (HCl) is a monoprotic acid, which means it can dissociate (i.e., ionize) only once to give up one H+ ion (a single proton).

In aqueous hydrochloric acid, the H+ joins a water molecule to form a hydronium ion, H3O+:[23][24]
HCl + H2O → H3O+ + Cl−

The other ion formed is Cl−, the chloride ion. Hydrochloric acid can therefore be used to prepare salts called chlorides, such as sodium chloride.