Sodium hydroxide (NaOH), commonly known as the caustic soda, caustic soda, KeXingNa because of another name, caustic soda and in Hong Kong and called elder brother, under normal temperature is a white crystal, has the strong corrosive. Soluble in water, the solution is strongly alkaline, can make phenolphthalein red. Sodium hydroxide is a very common chemical laboratory, is the alkali one of essential drugs. Its solution can be used as a twist.