Uses of Hydrochloric Acid in Chemistry and Industry

Hydrochloric acid, also commonly known as muriatic acid, is produced by dissolving hydrogen chloride gas in water. It is a strong and volatile acid with a distinctive pungent odour. It is isolated from its solution using the process of membrane distillation. In its gaseous form, hydrochloric acid is colourless and an extremely important laboratory reagent. It is found in the human body as a component of gastric secretion. Hydrochloride uses vary extensively and widely for the preparation of other chemical compounds and is of high commercial importance. The molecule of HCl has hydrogen and chlorine combined in a 1:1 ratio. It is also said to be salt if protonated with water and chloride. 

Here’s the Lewis Dot Structure of an HCL Molecule - 

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Uses of Hydrochloric Acid

Hydrochloric acid has extensive uses in diverse fields. Listed below are the purposes for what is hydrochloric acid used for-

• In the synthesis of Organic Compounds: Hydrochloric acid is used for the synthesis of a variety of organic compounds which in turn have varied uses. It is used to prepare dichloromethane, vinyl chloride, polyvinyl chloride, etc. These organic compounds have high commercial significance. These are used in the plastic industry. Hydrochloric acid is also used to synthesise bisphenol A which in turn is used to produce plastic.

• In preparation of aqua regia: Aqua regia is a yellow fuming liquid made by mixing concentrated nitric acid and concentrated hydrochloric acid in ratio 1:3. It can dissolve noble metals like platinum and gold. Aqua regia is used for cleaning and making jewellery.

• To purify table salt: HCl is used for the purification of table salts. In this, the impure salt is dissolved in water containing hydrochloric acid dissolved. Due to the common ion effect, NaCl ionisation is suppressed which results in the deposition of pure salt. 

• To maintain the pH of pharmaceutical products: Hydrochloric acid is known for its ability to maintain the acidic pH of a substance. Hence it is used to maintain the pH of a lot of substances.

• Synthesis of inorganic compounds: Numerous inorganic compounds are synthesized with hydrochloric acid being a primary reactant or catalyst. Examples of such compounds are poly aluminium chloride (PAC), iron (III) chloride, etc.

• Leather tanning industry: Hydrochloric acid is used for the tanning of leather. It changes the pH of the leather to prevent any bacterial growth on it.

• For purification of sugar: Hydrochloric acid is used for purification of sugar. Post the removal of xylose and glucose by acid hydrolysis of the sugarcane juice the rest of the organic substances in the solution are removed by hydrochloric acid which gives a concentrated solution.

• For pickling of steel: This is one of the most important uses of hydrochloric acid. Hydrochloric acid is a very strong acid and can you remove stains from metal bodies like iron, copper, and alloys like brass. For example, it can remove rust from iron. We should keep in mind that even for cleaning purposes it is used in a very dilute form. Technically 18% concentration of HCl is used in the pickling of carbon steel grades.

Fe3O4 + Fe +HCl 4   🡪   FeCl3 + 4H2O

• Cleaning properties: Due to its strength hydrochloric acid is used for cleansing purposes. It is used to clean tiles, bricks, etc. It is also used in the manufacture of chlorine dioxide gas which is an extremely strong disinfectant.

2NaClO3 + 4HCl 🡪  2ClO + 2NaCl + 2H2O

• Production and extraction of mineral oil: Hydrochloric acid is a great corrosive agent. It is hence injected into rocks containing mineral oil (petroleum). HCl formed large pores which assist oil production and extraction.

• To remove the hardness of water: Uses of HCl also extends to water cleaning. Hydrochloric acid is effective in regenerating resins in the ion exchange method. HCl  is used to remove the permanent hardness of the water.

• Chemical wastewater treatment: Due to high corrosiveness hydrochloric acid is used to remove scales in water formed due to various salts in the water. It acts as an emulsion breaker in the wastewater.

• In batteries: Hydrochloric acid is a powerful acid that dissociates to yield hydrogen ions which are the charge carriers in the battery. These ions complete the circuit to generate current.

Hydrochloric Acid: An Interesting Fact

Hydrochloric acid plays a very vital role in human digestion by triggering the digestive enzyme pepsin and helps in killing the bacteria entering the stomach. Hydrochloric acid is produced by the parietal cells of the gastric gland present in the stomach lining. In case of insufficient hydrochloric acid in the stomach which is known as Achlorhydria, the individual needs supremely diluted hydrochloric acid as a medicine. And here comes the hydrochloride tablet used as substitutes. A hydrochloride solution is also used in such a case. 

Hydrochloric acid is a very important chemical compound owing to its diverse usage in the laboratory and manufacturing industries. However, it should be handled with the utmost care and only under professional supervision. It is a highly corrosive acid and can cause serious skin burns. Direct contact with the skin should be avoided at any cost.