Hydrochloric acid is an aqueous solution of hydrogen chloride (HCl), which has a wide range of industrial uses. It is commonly used in metal pickling, alkaline sewage treatment, and production of various daily chemicals. Hydrochloric acid is a colorless and transparent liquid with strong pungent smell and high corrosiveness. Concentrated hydrochloric acid (mass fraction: about 37%) has strong volatility.
Hydrochloric acid comes from the chlor alkali industry. The chlor alkali industry converts seawater into chlorine gas, hydrogen and sodium hydroxide solution, and then further converts it into various chlorine containing substances such as hydrochloric acid. Since the consumption of sodium hydroxide in the products of the chlor alkali industry is greater than that of the chlorine containing substances, the price of hydrochloric acid is easily low due to oversupply. Therefore, if only acid is needed in industry, sometimes hydrochloric acid is used instead of sulfuric acid and other materials to reduce the cost to a certain extent.