Acids, Bases and Salts — Tech Evolutions

Entry	Year	Description	Impact
Contact Process for H2SO4	Early 20th Century (Industrialization)	The Contact Process is the primary industrial method for producing sulfuric acid (H₂SO₄). It involves the catalytic oxidation of sulfur dioxide (SO₂) to sulfur trioxide (SO₃) using vanadium pentoxide (V₂O₅) as a catalyst, followed by absorption of SO₃ in concentrated H₂SO₄ to form oleum, which is then diluted to produce sulfuric acid.	Revolutionized industrial chemistry, making H₂SO₄ widely available for fertilizers, detergents, and other chemical industries. Its efficiency and high yield are critical for modern manufacturing. This process is a cornerstone of the chemical economy.
Chlor-alkali Process for NaOH	Late 19th Century (Industrialization)	The Chlor-alkali process is an industrial method for the electrolysis of aqueous sodium chloride (brine) to produce sodium hydroxide (NaOH), chlorine gas (Cl₂), and hydrogen gas (H₂). Modern variants include diaphragm, mercury, and membrane cell processes, with membrane cells being the most environmentally friendly.	Essential for the production of NaOH (caustic soda), a strong base used in soap, paper, textiles, and alumina production. It also yields chlorine, vital for PVC, disinfectants, and water treatment, and hydrogen, an emerging energy carrier. This process is a key indicator of industrial chemical capacity.
Flue Gas Desulfurization (FGD)	Mid-20th Century (Environmental Awareness)	FGD is a set of technologies used to remove sulfur dioxide (SO₂) from the exhaust flue gases of fossil fuel power plants and other sulfur oxide emitting processes. Common methods involve wet scrubbing with limestone (CaCO₃) or lime (CaO) slurries, which react with SO₂ to form calcium sulfite/sulfate.	Crucial for mitigating acid rain and improving air quality. It directly addresses the environmental impact of industrial acid gas emissions, demonstrating the application of acid-base chemistry in pollution control and sustainable development. This technology is mandated in many countries to meet emission standards.