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Hydrochloric acid

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Hydrochloric acid (HCl) is a chemical compound composed of chlorine (Cl) and hydrogen (H).

Other names: hydrogen chloride, muriatic acid.

Hydrochloric acid
Hydrochloric acid

It has the chemical formula HCl and is one of the most common and essential acidic compounds. Hydrochloric acid is highly acidic and finds widespread use in various industrial and laboratory processes. It has a pungent odor and corrosive properties. In aqueous solutions, HCl dissociates into hydrogen ions (H+) and chloride ions (Cl-), which gives it its acidic nature.

Discovery of Hydrochloric Acid

It is difficult to ascertain who first obtained HCl and when. It is known that in the late 15th century, alchemist Basil Valentine and in the 16th century, Andreas Libavius, in their diligent search for the elixir of life, heated common salt with alum and copperas in their alchemical devices, obtaining a product they described as “spirit of salt.” This was, in fact, the hydrochloric acid we are familiar with today, although impure.

Later, in the 17th century, hydrochloric acid was discovered by Johann Rudolf Glauber, a German chemist and apothecary. Glauber obtained hydrochloric acid by burning salt containing chlorine with water. He described the obtained liquid as “marine acid” due to its origin from sea salt (sodium chloride). Since then, hydrochloric acid has become a subject of further research and finds extensive applications in various industrial and scientific fields.

Chemical Properties of Hydrochloric Acid

HCl possesses the following chemical properties:

  • Acidity: Hydrochloric acid is a strong acid. In aqueous solutions, it dissociates into hydrogen ions (H+) and chloride ions (Cl-), leading to a decrease in the pH of the solution and making it acidic.
  • Corrosiveness: HCl exhibits high corrosive activity. It can dissolve many metals, forming metal chlorides and releasing hydrogen gas.
  • Oxidizing Properties: Hydrochloric acid can act as an oxidizing agent in certain reactions. For example, it can oxidize iron to its ionic form (ferrous chloride) while simultaneously being reduced to chloride ions.
  • Electrolytic Dissociation: In aqueous solutions, hydrochloric acid completely dissociates into H+ and Cl- ions. This means that hydrochloric acid solutions are electrolytes capable of conducting electric current.
  • Reactions with Bases: HCl reacts with bases to form salts and water. For example, the reaction of HCl with sodium hydroxide (NaOH) produces sodium chloride (NaCl) and water (H2O).
  • Formation of Chlorides: HCl can react with various compounds, leading to the formation of chlorides. For instance, it forms copper chloride (CuCl2) upon reacting with copper oxide (CuO).

These are just a few of the main chemical properties of hydrochloric acid.

Production of Hydrochloric Acid

HCl can be produced through several methods. The primary methods of producing hydrochloric acid include:

  • Direct Synthesis: This method involves mixing chlorine (Cl2) with water (H2O) under specific conditions. The reaction yields hydrochloric acid. In this process, hydrogen ions (H+) and chloride ions (Cl-) are formed. Cl2 + H2O → HCl + HClO The obtained hydrochloric acid can be concentrated by evaporating the solution.
  • Reaction of Chlorides with Acids: HCl can be obtained by reacting metal chlorides with strong acids, such as sulfuric acid (H2SO4).
  • Electrolysis: Hydrochloric acid can also be obtained through the electrolysis of a sodium chloride (NaCl) solution. When an electric current passes through the solution, hydrochloric acid, chlorine gas (Cl2), and hydrogen gas (H2) are formed.

2NaCl + 2H2O → 2HCl + Cl2 + H2

These methods are used for the industrial-scale production of hydrochloric acid.

Applications of Hydrochloric Acid

HCl has a wide range of applications in various industries. Some of the main applications of hydrochloric acid include:

  1. Industry: Hydrochloric acid is used in a large number of industrial processes, including the production of polyvinyl chloride (PVC), chlorides, and organic compounds, as well as in the manufacturing of fertilizers and pharmaceuticals.
  2. Water Treatment: HCl is used for water purification and disinfection in municipal systems, pools, and spa centers. It is also used for cleaning pipelines and equipment in industries.
  3. Laboratory Research: HCl is an important reagent in chemical and biological laboratories. It is used for pH regulation of solutions, sample preparation for analysis, and other chemical processes.
  4. Food Production: HCl is used in the food industry for pH regulation, preservation of food products, and the production of certain food additives.
  5. Electronics and Metallurgy: HCl is used for cleaning and surface treatment in the electronics industry and metallurgical processes, such as galvanic coatings.
  6. Medicine: HCl is used in some medical procedures, such as the removal of warts and tumors through coagulation.