Alcalis

Alcalis, or alkalis, are bases that dissolve in water to form alkaline solutions. In aqueous solution they typically produce hydroxide ions (OH−), resulting in a pH above 7. While all alkalis are bases, not all bases are alkalis. Alkalis can be strong, dissociating completely in water, or weak, dissociating only partly.

Common examples of alkalis include sodium hydroxide (NaOH) and potassium hydroxide (KOH), which are strong alkalis widely used in industry for pH control, soap making, and chemical synthesis. Calcium hydroxide (Ca(OH)2) is another alkali, though it is less soluble in water and often used in water treatment and soil stabilization. Ammonia (NH3) dissolved in water forms ammonium hydroxide (NH4OH) and acts as a weaker alkali. Other alkalis include lithium hydroxide and, in some contexts, various alkali metal carbonates and bicarbonates that generate hydroxide ions in solution.

Properties of alkalis include a tendency to neutralize acids, forming salts and water in neutralization reactions. They also react with acids in substitution or redox processes and can react with carbon dioxide to form carbonates, which is utilized in flue-gas scrubbing and water softening. Alkalis have wide-ranging applications in cleaning, paper production, food processing, petroleum refining, and pharmaceuticals.

Safety considerations are important: many alkalis are caustic and can cause chemical burns or eye damage. Proper handling, storage, and protective equipment are advised when working with concentrated solutions or solid alkalis.