Sodium hydroxide, also known as lye or caustic soda (NaOH), is a white caustic metallic base used extensively in various industries, including pulp and paper, textiles, and as a drain cleaner. It is available in different forms and is highly soluble in water and other solvents; it also absorbs moisture from the air. Global production in 2004 was around 60 million tonnes, with a demand of 51 million tonnes.