According to Encyclopædia Britannica, an alkali is a classification word in chemistry used for any of the alkali metals that are soluble by hydroxide or water. They are strong bases that turn litmus paper from red to blue. Examples of alkali are lithium, sodium, potassium, rubidium and cesium.
Encyclopædia Britannica explains that some stages of alkali are used frequently in consumer goods. Soda ash and caustic soda are industrially manufactured alkali, and they are used to make: glass, soap, miscellaneous chemicals, rayon, cellophane, paper, pulp, aluminum and other metals, cleansers, detergents, textiles, water softeners, bicarbonate of soda, gasoline and other forms of fuel. Other manufactured alkali include potassium hydroxide, potash and lye.