After being ionized in water, it has surface activity and with negative charged which is called an anionic surfactant.
Anionic surfactants are the products with the longest history, the largest capacity and the most varieties among surfactants. Anionic surfactants are divided into sulfonate and alkyl Sulfate according to the structure of their hydrophilic groups, which are currently the main categories of anionic surfactants. The various functions of the surfactant are mainly found expression in changing the properties of the liquid surface, liquid-liquid interface and liquid-solid interface, of which the surface (boundary) properties of the liquid are the key point.