Alkali salt

Lore & Background

Alkali salts are the product of incomplete neutralization of a strong base and a weak acid. Their defining characteristic is their basic nature, which distinguishes them from neutral salts. This basicity occurs because the conjugate base derived from the weak acid undergoes hydrolysis in water, yielding a basic solution.

For instance, in sodium carbonate, the carbonate ion from carbonic acid hydrolyzes to create a basic solution, while the chloride ion from hydrochloric acid in sodium chloride does not hydrolyze, leaving sodium chloride neutral. A basic salt is distinct from an alkali: an alkali is a soluble hydroxide compound of an alkali metal or alkaline earth metal, whereas a basic salt is any salt that hydrolyzes to form a basic solution. These materials are highly soluble in polar solvents.

However, many alkali salts are insoluble and are obtained through precipitation reactions. In practical applications, alkaline salts—often the major component of alkaline dishwasher detergent powders—may include alkali metasilicates, alkali metal hydroxides, sodium carbonate, and sodium bicarbonate. Other strongly alkaline salts include sodium percarbonate, sodium persilicate, and potassium metabisulfite.

Reader's Guide

The distinction between a basic salt and an alkali is important: an alkali is the soluble hydroxide compound of an alkali metal or an alkaline earth metal, while a basic salt is any salt that hydrolyzes to form a basic solution. Another definition describes a basic salt as one that contains both hydroxide and other anions, such as white lead (basic lead carbonate or lead carbonate hydroxide). Alkali salts are insoluble and are obtained through precipitation reactions. They are widely used in products like alkaline dishwasher detergent powders, where common examples include alkali metasilicates, alkali metal hydroxides, sodium carbonate, and sodium bicarbonate.