Both caustic soda and soda from caustic soda factories are soluble in water and are strongly alkaline, providing Na + ions. These properties make them widely used in soap making, textile, printing and dyeing, bleaching, paper making, refined petroleum, metallurgy and other chemical industries. Common soap is sodium salt of high fatty acid, which is usually made by saponification of oil under the action of slightly excessive caustic soda. If fatty acid is used as raw material directly, soda can also be used instead of caustic soda to make soap.

In metallurgical industry, the effective components in ores are often converted into soluble sodium salts in order to remove insoluble impurities. Therefore, soda (which is also a flux) is often added, and sometimes caustic soda is also used. For example, in the process of aluminium smelting, both soda and caustic soda are used in the preparation of cryolite and the treatment of bauxite. For example, when tungsten is smelted, the concentrate and soda are first roasted into soluble sodium tungstate, then the powdered tungsten is prepared by acidification, dehydration and reduction. In chemical industry, caustic soda is used to make sodium metal and electrolytic water. Many inorganic salts, especially sodium salts (such as borax, sodium silicate, sodium phosphate, sodium dichromate, sodium sulfite, etc.) are produced by caustic soda or soda ash. Soda or soda are also used in synthetic dyes, drugs and organic intermediates.