Hydrochloric Acid (HCl) Engr. Muhammad Sajid Lecturer Department of Chemical Engineering University of Gujrat, Pakistan Contents Introduction History Properties Production Process Uses Health Safety and Environment Introduction Hydrochloric acid is a clear, colorless, highly pungent solution of hydrogen chloride (HCl) in water. It is a highly corrosive, strong mineral acid with many industrial uses. Hydrochloric acid is found naturally in gastric acid. About 20 million tonnes of hydrochloric acid are produced worldwide annually. introduction Hydrochloric acid (HCl) is listed as a Title III Hazardous Air Pollutant. Hydrochloric acid is a versatile chemical used in a variety of chemical processes, including hydrometallurgical processing (e. g., production of alumina and/or titanium dioxide), chlorine dioxide synthesis, hydrogen production, activation of petroleum wells, and miscellaneous cleaning/etching operations including metal cleaning (e. g., steel pickling). Also known as muriatic acid, HCl is used by masons to clean finished brick work, is also a common ingredient in many reactions, and is the preferred acid for catalyzing organic processes. One example is a carbohydrate reaction promoted by hydrochloric acid, analogous to those in the digestive tracts of mammals. history It was historically called acidum salis, muriatic acid, and spirits of salt because it was produced from rock salt and green vitriol (by Basilius Valentinus in the 15th century) and later from the chemically similar substances common salt and sulfuric acid (by Johann Rudolph Glauber in the 17th century). Free hydrochloric acid was first formally described in the 16th century by Libavius. Later, it was used by chemists such as Glauber, Priestley, and Davy in their scientific research History Aqua regia, a mixture consisting of hydrochloric acid and nitric acid, prepared by dissolving sal ammoniac in nitric acid, was described in the works of Pseudo-Geber, the 13th-century European alchemist.Other references suggest that the first mention of aqua regia is in Byzantine manuscripts dating to the end of th Free hydrochloric acid was first formally described in the 16th century by Libavius, who prepared it by heating salt in clay crucibles. Other authors claim that pure hydrochloric acid was first discovered by the German Benedictine monk Basil Valentine in the 15th century, by heating common salt and green vitriol, whereas others claim that there is no clear reference to the preparation of pure hydrochloric acid until the end of the sixteenth centurye thirteenth century. Appearance: colorless, fuming liquid Odor: pungent odor Boiling point: 53C (127F) Melting point: -74C (-101F) Solubility: infinite in water with slight evolution of heat Vapor pressure: 190 mm Hg @ 25C (77F) Density: 1.18 (water = 1) Physical Properties Its boiling, melting points, density and pH depends on concentration of HCl in aqueous Solution. M.P B.P Density Vapor Density Vapor F.P pressure Storag e Temp. Form Water Solubility -35°C 57°C 1.2 g/mL at 25 °C(lit.) 1.3 vs air 613 psi 21.1°C 2-8°C Liquid Miscible -40°C Production Of HCl Hydrochloric acid may be manufactured by several different processes, although over 90 percent of the HCl produced in the world is a byproduct of the chlorination reaction. Production Of HCl Synthesis from elements (Burning Process) Organic By-product Synthesis. Metallic chlorides with Sulfuric acid. Waste Incineration. Thermal decompsition of hydrated heavy metals Organic by-product Synthesis Hydrochloric acid is made during chlorination of organic products as follows: RH â‚‚ + Cl â‚‚ →RCl + HCl Hydrochloric acid is also made during fluorination of chlorinated organic products to manufacture (hydro) chlorofluorocarbons as follows: RCl + HF → RF + HCl Where RCl stands for chloroform, trichloro ethane, etc and RF stands for (hydro) chlorofluorocarbons Organic by-product Synthesis Chlorination Gases Chlorination Process HCl Absorption HCl & Cl2 Vent Gas Scrubber Dilute HCl Concentrated HCL Sulfuric Acid Method HCl is Generally made in Industries by the Action of Sulphuric Acid on Common salt NaCl. 1) NaCl +H2S04 ------> NaHS04 +HCl 2) NaHS04 +NaCl -------> Na2S04 + HCl These reactions may be carried out by heating the mixture of salt and sulfuric acid either in an "open roaster," or in a muffle or "close roaster." These are both called "salt-cake furnaces." Organic Waste Incineration Hydrochloric acid is made during Incineration, at high temperatures, of chlorinated wastes as follows. HCCl=CCI2 + 3.502+ CH4 3C02 + 3HCl + H20 HCCl=CCI2 + 1.502+ H20 2C02 + 3HCl C4H6Cl2 + 5O2 4CO2 + 2HCl Thermal decomposition of hydrated heavy metal chlorides HCl is also produced by thermal decomposition of hydrated heavy metal chlorides from spent pickle liquor in metal treatment as; 2FeCl3 + 6H2O Fe2O3 + 3H2O + 6HCl Burner Process Chlorine and hydrogen react exothermally to form hydrogen chloride gas as follows: Clâ‚‚+ Hâ‚‚ → 2HCl Both gases pass through a burner nozzle, and are ignited inside a graphite combustion chamber, which is cooled by water. The hydrogen chloride gas produced is cooled, and absorbed into water to give hydrochloric acid at the desired concentration. Synthesis from elements Uses For pickling Steel For the manufacturing of PVC pipes For the production of compounds that used in waste water treatment For manufacturing of Dyes and Fertilizers It is used in textile and rubber industries USES Uses by Country Health Safety & Environment Concentrated hydrochloric acid (fuming hydrochloric acid) forms acidic mists. Both the mist and the solution have a corrosive effect on human tissue, with the potential to damage respiratory organs, eyes, skin, and intestines irreversibly. Upon mixing hydrochloric acid with common oxidizing chemicals, such as sodium hypochlorite (bleach, NaClO) or potassium permanganate (KMnO4), the toxic gas chlorine is produced. NaClO + 2 HCl → H2O + NaCl + Cl2 2 KMnO4 + 16 HCl → 2 MnCl2 + 8 H2O + 2 KCl + 5 Cl2 PbO2 + 4 HCl → 2 H2O + PbCl2 + Cl2 Health Safety & Environment Personal protective equipment such as latex gloves, protective eye goggles, and chemical-resistant clothing and shoes will minimize risks when handling hydrochloric acid. The United States Environmental Protection Agency rates and regulates hydrochloric acid as a toxic substance.[36] The UN number or DOT number is 1789. This number will be displayed on a placard on the container.
