Hydrochloric acid

Hydrochloric acid (hydrogen chloride).
Molecular formula : HCL
(Cl = 97,23 %, H = 2,76 %)

Molar mass = 36,461 ± 0,002 g·mol^-1

Formerly called "spirit of salt" or muriatic acid. This acid is a colorless liquid with a pungent odor. Concentrate can have a pH less than 1, and very corrosive.
Pure hydrochloric acid does not exist on Earth in natural state. However, this is a chemical species that has been frequently used in history from the beginnings of chemistry (using salts in presence of sulfuric acid, Jabir Ibn Hayyan Persian alchemist discovered hydrochloric acid from sodium chloride, about the year 800).
Note : HCl is the major component of gastric acid. It is present in the stomach where it helps the digestion of food.

Preparation.
Reacting the Cl₂ chlorine gas which reacts with slight excess of H₂ dihydrogen, to produce hydrogen chloride gas HCl (the reaction takes place in a burner, to 2000 ° C).

Then the latter is absorbed in water:

Other methods based on same principle of "burning" of carbon (coke) and sulfur dioxide in presence of chlorine and water vapor:

Reaction between H2SO4 (sulfuric acid) and chloride Cl:
(2-step reaction with salt containing chloride [mCl])

Note:
The first reaction takes place at 150 to 300° C, while second stage requires a temperature of about 550 to 600° C and excess salt.
The Mannheim and Berlin process using this synthetic route.

Main features:
The physical properties of hydrochloric acid, such as boiling point or melting, depend on the concentration (or molar aqueous HCl solution). They since the physical properties of water varies from 0% HCl to those of fuming hydrochloric acid for higher fractions of 40% HCl.

The reference temperature and pressure for the above table are 20 °C and 1 atmosphere (101.325 kPa).

Technical solutions :

• 10 to 12% (density: about 1048 kg/m3)
• 30-34% (density: 1149 à 1169 kg/m3)

In water treatment, it is used in the injection water as dilute commercial solutions.

A formulation for the water treatment.
Reaction mechanism of calcium bicarbonates (simplified equations):

With 1 mg as HCl added, there has (10/73) = 0.137°F for lower TAC, and 1.205 mg as free CO2 and (71/73)= 0.97 mg/L as Cl chloride formed.

Storage.
Tightly closed and dry in a well ventilated area.
For current storage: no metal containers.

Uses.

• water treatment (drinking, waste and industrial) and treatment pools
• household cleaner
• used in many industrial processes, including:
  • construction
  • leather processing
  • fertilizer manufacturing
  • oil production
  • pickling and descaling metal
  • producing inorganic compounds
  • regeneration of ion exchange resins
  • manufacture of various chlorides and metallic salts
  • production of food ingredients and food additives

Health-wise.

• Inhalation: vapors may be fatal
• Ingestion: toxic, sometimes fatal
• Skin: May cause severe injury
• Eyes very dangerous

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Sources : personal and Wikipedia, the free encyclopedia.

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