Alkalies

Alkalis are bases that dissolve in water to form alkaline, or basic, solutions. They release hydroxide ions (OH−) in aqueous solution and neutralize acids, increasing the pH. The term is usually reserved for soluble bases, especially hydroxides and certain carbonates of alkali metals such as lithium, sodium, potassium, rubidium, and cesium. Common examples include sodium hydroxide (NaOH) and potassium hydroxide (KOH), which are strong alkalis, and ammonium hydroxide (NH4OH), a weaker alkali. Soluble carbonates, such as sodium carbonate (Na2CO3) and potassium carbonate (K2CO3), also function as alkalis because they generate OH− in water.

Alkalis contrast with many bases that are insoluble in water; those bases are not typically classified as alkalis. Alkalis in solution form basic environments that can turn red litmus blue and have high pH values. Strong alkalis are highly caustic and can react vigorously with acids and organic materials; weaker alkalis also pose hazards but to a lesser degree.

Occurrence and uses: Alkalis occur in nature as components of alkaline soils and certain minerals. In industry, they are used for pH control, chemical synthesis, and cleaning. Common applications include caustic solutions in soap making, water treatment, and food preparation (for example, baking soda, NaHCO3, as a mild alkali).

Safety: Handling alkalis requires protective equipment due to their caustic nature. They should be stored protected from moisture and incompatible substances, especially acids, to prevent dangerous reactions. The word alkali derives from historical terms referring to ashes used to produce alkali in processing.