Caustic Soda Liquid (Lye)

About This Product

Caustic soda liquid, also called caustic soda lye or sodium hydroxide solution, is NaOH dissolved in water; the CAS number 1310-73-2 refers to the hydroxide itself. It is a clear, colourless, odourless liquid, strongly alkaline and appreciably denser than water. The case for buying caustic as a solution rather than a solid is that somebody has already done the dissolving. Sodium hydroxide releases a large amount of heat as it dissolves, enough to boil a poorly agitated make-up tank, and solid caustic is a dusty, deliquescent, corrosive material to charge by hand. A plant taking 32 or 50 percent lye pumps it straight into the process, meters it accurately and never opens a drum. The two strengths behave differently in the cold, and that usually decides which one a site can take. Fifty percent lye crystallises at about 12 degrees Celsius and needs heated or traced tanks and lines through a temperate winter; 32 percent stays liquid down to around minus 20 degrees but carries nearly twice the water for the same NaOH, so freight costs more per tonne of active alkali. Sites in warm climates and those with steam tracing generally take 50 percent, and those without take 32 percent. It is used for pH correction and neutralisation in water and effluent treatment, in mercerising and scouring in textile dyeing and printing, in soap and detergent manufacture, and as the alkali in a wide range of chemical processes. Bio Green Chem supplies caustic soda lye at 32 and 50 percent NaOH in 1.5 tonne IBC totes, twenty to a container, or in bulk. It is UN 1824, Class 8, and is corrosive to skin and eyes; handle to the safety data sheet.