What is Hydrochloric acid?

Hydrochloric acid is a strong, colorless liquid with a pungent smell, derived from dissolving hydrogen chloride gas in water. It is among the most important industrial chemicals, and its application is found everywhere due to its strong acidic nature. Hydrochloric acid, in its natural form, is present as gastric acid in the stomach and plays a very significant role in the digestion of food material. Its versatility extends to varied industries, from steel production to chemical manufacturing and food processing.

History

History itself shows that hydrochloric acid has been in use for more than a millennium. About 800 AD, the famous alchemist Jabir ibn Hayyan documented for the first time the production of HCl by combining common salt with vitriol (early sulfuric acid). His pioneering writings preserved valuable knowledge about HCl for centuries.

In the 18th century, British chemist Joseph Priestley isolated hydrochloric acid in its gaseous state and called it “marine acid air.” In 1818, Sir Humphry Davy, using more sophisticated chemistry, identified hydrogen and chlorine as the key elements of HCl. Hydrochloric acid was a major byproduct of the Leblanc process developed during the Industrial Revolution. The capture of the chemical was regulated under the 1863 Alkali Act and it thus turned into a very useful industrial chemical.

physical and chemical properties

Physical Properties

• Color: Colorless
• Odor: Pungent
• State: Liquid
• Melting point: -74 °C (-101 °F)
• Boiling point: 85 °C (185 °F)
• Density: 1.18 g/cm³
• Appearance: HCI is a colorless liquid.
• Viscosity: HCI has a slightly higher viscosity than water.
• Solubility: HCI is miscible with water in all proportions.
• Electrical conductivity: HCI is a good conductor of electricity because it dissociates into hydrogen and chloride ions in solution.

Chemical Properties

• Chemical formula: HCl
• Acidity: HCI is a strong acid, meaning it readily donates a hydrogen ion (H+) to other substances.
• Corrosiveness: HCI is a corrosive substance that can attack metals, skin, and other materials.
• Reactivity: HCI reacts with many metals to produce hydrogen gas. It also reacts with bases to produce salts.

Production Process

Hydrochloric acid is mainly produced by the chlor-alkali process, involving the electrolysis of brine-sodium chloride solution. The products obtained from this process are sodium hydroxide, commonly known as caustic soda, chlorine gas (Cl2), and hydrogen gas (H2). Hydrogen and chlorine gases are combined to produce HCl, which is dissolved in water to desired concentrations. Industrial hydrochloric acid is usually about 99% pure.

Applications and uses of hydrochloric acid

Industrial Applications:

• Steel Pickling: HCI is an essential part of steel pickling. In this process, steel is prepped for further processing by removing impurities like rust or iron oxide scale. The acid dissolves these unwanted elements, leaving behind clean steel ready for tasks like extrusion, rolling, or galvanizing.
• Chemical Production: HCI acts as a key building block in the production of a vast array of chemicals. It contributes to the creation of everyday items like PVC plastic and polyurethanes, used in everything from building materials to clothing. It’s also involved in the production of certain food additives, though these applications ensure minimal HCI remains in the final product.
• Oil Production: Oil extraction can be enhanced through a process called acidizing, which utilizes HCI. The acid is injected into the rock formations surrounding an oil well. This dissolves a portion of the rock, creating larger pores that allow for easier oil flow to the well, ultimately increasing oil production efficiency.
• Regenerating ion exchangers: These are used in water treatment, and HCI helps restore their effectiveness in removing impurities from water.
• Wastewater management: Here, hydrochloric acid helps adjust the pH levels of wastewater streams, ensuring they comply with environmental regulations before release.
• Salt purification: Hydrochloric acid plays a role in purifying table salt by removing unwanted minerals.
• Leather processing: In the leather tannin. In the Ng industry, hydrochloric acid helps prepare animal hides for processing into leather.

Household Applications (diluted form):

• Cleaning: Hydrochloric acid’s ability to dissolve mineral deposits makes it a valuable ingredient, in diluted forms, for some household cleaners. It tackles tough stains on bathroom tiles, porcelain sinks, and toilet bowls, leaving surfaces disinfected and gleaming.
• Food Processing: Hydrochloric acid finds application in the food industry but in strictly controlled settings and minimal quantities. Here, it acts as an acidifier in certain foods and beverages. This can serve various purposes, from controlling flavor profiles to enhancing preservation in some products.

hydrochloric acid Packing

• Plastic drums: High-density polyethylene (HDPE) drums are common for commercial quantities of HCI. They come in various sizes and offer good chemical resistance.
• IBC tanks: Intermediate Bulk Containers (IBCs) are large plastic totes used for transporting bigger volumes of hydrochloric acid (up to several hundred gallons). They are typically placed on pallets for easy handling.
• Stainless steel tanks: For very large volumes or high-concentration hydrochloric acid, manufacturers may use corrosion-resistant stainless steel tanks for transport.

hydrochloric acid Safety 

Gear up: Wear gloves, goggles, and a lab coat/apron. Consider a respirator for concentrated solutions or poor ventilation.

Work ventilated: Fumes are irritating, use a fume hood or ensure good ventilation.

Mix with care: Never mix hydrochloric acid with other chemicals unless you know it’s safe. Always add acid slowly to water, never the other way around.

Clean spills carefully: Wear PPE first, then neutralize spills with baking soda solution.

Store smart: Keep it cool, dry, and sealed in the original container. Out of reach of children and pets.

Dispose responsibly: Don’t pour it down the drain! Follow local regulations for hazardous waste disposal.

In case of emergency: Know where the safety shower and eyewash station are. If in contact with hydrochloric acid, get medical attention immediately.