Sodium hydroxide bottle and pellets. The bottle contains sodium hydroxide solution (NaOH, caustic soda). The watch glass contains sodium hydroxide pellets. Sodium hydroxide is the most-used base (alkali) in chemical laboratories. It is used to drive chemical reactions and also for the neutralisation of acidic materials. It is highly corrosive and is commonly used to unblock drains. It was also traditionally used in soap making and is used in paper production among other applications.