STRAW CAUSTIC

Pure sodium hydroxide is a colorless crystalline solid that melts intact at 318°C. Highly soluble in water, low solubility in ethanol and methanol, but insoluble in ether and other non-polar solvents.

Similar to the hydration of sulfuric acid, dissolving solid sodium hydroxide in water is an extremely exothermic reaction and can generate large amounts of heat, posing a threat to safety and spattering. The resulting solution is usually colorless and odorless. Like other alkaline solutions, it becomes slippery when in contact with the skin.

Sodium hydroxide reacts with protic acid to form water and related salts. For example, when sodium hydroxide reacts with hydrochloric acid, sodium chloride is formed:

NaOH (aqueous solution) + HCl (aqueous solution) → NaCl (aqueous solution) + H2O (l)

Usually, such a neutralization reaction is represented by a simple net ionic equation:

OH- (aqueous solution) + H + (aqueous solution) → H2O (I)

This reaction with strong acids generates heat and therefore exotherms. These acid-based reactions can also be used for titration. However, sodium hydroxide cannot be used as the main standard, as it is hygroscopic and can absorb carbon dioxide from the air.