Caustic soda flakes (sodium hydroxide, NaOH, CAS 1310-73-2) are one of the most widely traded industrial alkalis. Flakes are dry, easy to dose and easy to pack, which is why they are the usual form for bagged export shipments.
Forms of caustic soda
Sodium hydroxide is sold as flakes, pearls (prills), solid blocks and as a solution, most often at 48 to 50 percent. Flakes and pearls travel in bags, while solution moves in tanks. For exporters and distant buyers, solid forms are usually easier to ship and store.
Specification points to compare
- NaOH content: commonly 98 to 99 percent on a dry basis. A bag marked minimum 99 percent is a higher grade than one at 98 percent.
- Sodium carbonate (Na2CO3): forms when caustic soda meets carbon dioxide in the air, so a high value can point to poor storage or ageing.
- Sodium chloride (NaCl): depends on the production route. Membrane-cell caustic usually carries much less chloride than diaphragm-cell caustic.
- Iron and heavy metals: matter for textile, chemical and food-related uses.
- Appearance and flake size: white, free-flowing flakes without lumps.
Main applications
- Soap and detergent manufacturing
- Pulp and paper
- Textile processing and mercerizing
- Alumina refining (Bayer process)
- Water treatment and pH adjustment
- Chemical and petroleum processing
Packaging, storage and transport
Caustic soda absorbs moisture and carbon dioxide from the air, so bags must stay sealed and dry. Typical export packaging is 25 kg bags or jumbo bags of about one ton. Solid sodium hydroxide is a corrosive dangerous good (class 8, UN 1823), so shipments need correct labelling and a current safety data sheet. The customs tariff heading is usually 2815.11.
