Caustic soda is widely used in wood pulping to make paper or recycled fibers. Together with sodium sulfide, sodium hydroxide is a key component of the white liquid solution used to separate lignin from cellulose fibers in the kraft paper process. It also plays a key role in several later stages of bleaching the brown pulp produced by the pulping process. These stages include oxygen delignin, oxidative extraction and simple extraction, all of which require a strongly alkaline environment with a pH > 10.5 at the end of the stage.

organization

In a similar manner, sodium hydroxide is used to digest tissue, as in a process used on farm animals. The process involves placing the body in an airtight chamber and then adding a mixture of sodium hydroxide and water (which breaks the chemical bonds that hold the body together). This eventually turns the body into a liquid similar in appearance to coffee, with the only solid left being bone shells that can be crushed between fingertips.

Sodium hydroxide is often used to break down road debris dumped in landfills by animal treatment contractors. Because of its availability and low cost, it has been used by criminals to dispose of dead bodies. Italian serial killer Leonarda Cianciulli used the chemical to turn bodies into soap. In Mexico, a man working for a drug cartel admitted using it to dispose of more than 300 bodies.

Sodium hydroxide is a dangerous chemical because it can hydrolyze proteins. If the diluted solution spills onto the skin, it may cause burns if the area is not thoroughly cleaned and rinsed with running water for several minutes. Splash into the eye can be more serious and can lead to blindness.

Esterification and transesterification reagents

Sodium hydroxide is traditionally used to make soap (cold soap, saponification). It was made in the 19th century for hard surfaces rather than liquid products because it was easier to store and transport.

For biodiesel production, sodium hydroxide is used as a transesterification catalyst for methanol and triglycerides. This only works with anhydrous sodium hydroxide, because when combined with water, the fat turns into soap, and the soap becomes contaminated with methanol. NaOH is more commonly used than potassium hydroxide because it is cheaper and requires less. NaOH made from salt is cheaper than potassium hydroxide because of production costs.