Sodium carbonate

Sodium carbonate, better known by its commercial name "soda ash", is among the most-produced chemicals worldwide — about 60 Mt/yr. Its industrial centrality comes mainly from the glass industry (~50 % of world consumption): added to silica at ~15 %, it lowers sand's melting point from 1700 to 1500 °C, massive energy savings at furnace scale. This property democratised soda-lime glass from late antiquity onward and makes it today's bottle, window and windshield glass.

The history of its production tells two centuries of industrial battle. Until the 18th century, it was extracted from marine seaweed ashes (the "plant soda" of Venetian glassmakers) or from evaporitic deposits (Egyptian natron, Wyoming salt lakes). The Leblanc process (1791), from NaCl + H₂SO₄ + CaCO₃, enabled the first massive industrial production — at the cost of catastrophic toxic emissions (HCl) and acidic effluents (CaS). The Solvay process (1861) supplanted it using NaCl + CaCO₃ + recirculated NH₃ in a closed loop, with CaCl₂ as the only discharge — an efficiency model that still dominates today (>80 % of world production).

In the United States, half the production directly mines trona evaporitic deposits (Wyoming), bypassing the Solvay step: these deposits formed when salt lakes dried out in the Pliocene and offer near-pure Na₂CO₃ recoverable by dissolution-crystallisation. This "natural" route is more energy-efficient (~30 % less energy) and emits half the CO₂ of Solvay — hence Europe's chronic Na₂CO₃ trade deficit vs the United States. Beyond glass, Na₂CO₃ also feeds detergents (water softener, builder), acid-effluent treatment, the cellulose industry and fine inorganic chemistry.