Alkalis: alkali metals, industrial soda and modern safety

This update explains what alkalis are, their etymology, historical manufacture (Leblanc) and the dominant Solvay (ammonia-soda) process. It covers modern production routes for sodium carbonate and sodium hydroxide (including brine electrolysis), common uses, and current first-aid guidance for alkali exposure.

What are alkalis?

In chemistry, "alkali" refers to strongly basic substances and historically to the group of alkali metals: lithium, sodium, potassium, rubidium, cesium and francium. Their hydroxides (for example, sodium hydroxide and potassium hydroxide) are white, deliquescent solids that dissolve readily in water to give slippery, soapy solutions that turn acid-base indicators (litmus, methyl orange and others) to their basic colors.

Name and early manufacture

The word alkali comes from the Arabic al-qaly, meaning "ashes," because soda (sodium carbonate) and potash were originally obtained from plant ashes. For centuries that was the only source of soda ash.

In the late 18th and 19th centuries two industrial processes dominated soda ash production. The Leblanc process, developed in the 1790s, converted salt into sodium carbonate by a multi-step reaction that also produced hydrogen chloride and sulfur as valuable by-products. It was largely replaced by the Solvay (ammonia-soda) process developed by Ernest Solvay in the 1860s.

The Solvay process and modern production

The Solvay process uses brine, ammonia and carbon dioxide to precipitate sodium bicarbonate:

NaCl + NH3 + CO2 + H2O → NaHCO3 + NH4Cl

The sodium bicarbonate is heated (calcined) to form sodium carbonate and release CO2 and water. Ammonia is regenerated by treating the ammonium chloride with lime in a causticizing step, which produces calcium chloride as a major waste stream. The Solvay process persisted because it yields a pure product and recovers most ammonia; large-scale production today still relies on variants of this process and on mining or synthetic routes depending on regional industry.

Caustic soda (sodium hydroxide, NaOH) is produced industrially by two main routes: causticizing sodium carbonate with slaked lime (Ca(OH)2) - Na2CO3 + Ca(OH)2 → CaCO3 + 2 NaOH - and by electrolyzing brine in modern membrane or diaphragm cells. Electrolysis produces NaOH together with chlorine gas and hydrogen, both commercially valuable.

Uses and hazards

Alkalis are essential in glassmaking, paper, soaps, detergent manufacture, water treatment and many chemical syntheses. They are corrosive: concentrated hydroxides and carbonates cause chemical burns on skin and severe injury if swallowed.

First aid for alkali contact focuses on immediate and prolonged irrigation with water, removal of contaminated clothing, and rapid medical assessment. Do not induce vomiting or attempt to neutralize a strong alkali with acid. For suspected ingestion, contact local poison control or emergency services immediately.

Brief note on household remedies

Historically, mild alkalis such as dilute ammonia or baking soda were suggested for insect stings, but modern first aid emphasizes cleaning the site, cold compresses and antihistamines for itching; treat systemic allergic reactions with epinephrine and urgent medical care.