Sodium Hydroxide Solution 50% is a highly concentrated, viscous, and colorless aqueous solution containing roughly 50% NaOH by weight. It is a powerful base (caustic soda/lye) used in industrial applications, such as chemical synthesis, pulp/paper manufacturing, detergents, and industrial cleaning. It causes severe skin burns and eye damage.In analytical chemistry, a 50% (w/w) sodium hydroxide solution is frequently called a Sorensen solution. It is the standard starting point for preparing precise diluted solutions, such as 1N or 0.1N NaOH. Because sodium carbonate is nearly insoluble in 50% NaOH, it settles to the bottom of the bottle. This allows chemists to pipette pure, carbonate-free hydroxide from the middle of the solution, which is essential for accurate titration