GB/T 1146.1-1997 "National Standard for Ultrapure Water in China's Electronics Industry" stipulates two grades of ultrapure water: EW-I and EW-II. Among them, the EW-I grade requires a resistivity of not less than 18 MΩ .cm when it reaches 25 ° C, and not less than 17 MΩ .cm 95% of the time; There are detailed limit requirements for silicon, number of particles, number of bacteria, and various indicators such as copper, zinc, nickel, sodium, potassium, chlorine, nitrate, phosphoric acid, and sulfate. The standard aims to ensure the mass Stability and safety of ultrapure water in the application of the electronics industry.