Sodium hydroxide is sometimes called caustic soda or lye. It is a common ingrediet in cleaners and soaps. At room temperature, sodium hydroxide is a white, odorless solid. Liquid sodium hydroxide is colorless and has no odor.
Sodium hydroxide is an alkali substance, also known as lye, that is commonly used to make soap. Alkali is necessary for soap because it reacts with the oil (fat) and creates soap in a process called saponification