Why is NaOH called caustic soda?

Sodium hydroxide (NaOH) is commonly called caustic soda because of its highly corrosive nature. It is a strong alkali that can react with organic tissues, including skin, proteins, and fats, causing chemical burns. This property of NaOH gives it the name “caustic,” which comes from the Latin word causticus, meaning “burning.”

NaOH is an inorganic base that dissociates completely in water to produce hydroxide ions (OH⁻). These hydroxide ions attack organic compounds by breaking down complex molecules like proteins and fats into simpler substances. This reaction with organic matter is the reason NaOH must be handled with care in laboratories and industries.

Although NaOH is used in various chemical processes, it is not called caustic soda because of its use in soda water, which involves sodium bicarbonate, not NaOH. It is also used in soap making, where it reacts with fats to form soap in a process called saponification, but the name “caustic soda” is specifically due to its corrosive action. Reactions with chlorine gas are part of chemical synthesis but are unrelated to the caustic name.

Caustic soda has numerous industrial applications, such as paper manufacturing, cleaning agents, water treatment, and chemical synthesis. Its corrosive property is utilized to remove impurities and organic residues. The ability of NaOH to corrode organic tissues is also fundamental in organic chemistry laboratories, where it is used to break down complex molecules.

The term “caustic soda” highlights the chemical property of corrosion. It emphasizes the need for protective handling due to its reactivity with organic matter, making NaOH one of the most important yet potentially hazardous inorganic chemicals.