GB/T 15452-2009 The EDTA Titrimetric method is used to determine the content of calcium and mg ions in industrial circulating chilled down water. It is suitable for various industrial circulating chilled down water systems. Taking advantage of the characteristics that EDTA can form stable complexes with calcium and mg ions, calcium and mg ions are titrated successively with EDTA standard solution by controlling the pH value of the solution. The standard specifies the requirements of Burette and other instruments, and specifies the preparation of reagents. Detailed description of water sample collection, storage and pretreatment steps. Standardize the titration operation process, including titration speed, indicator selection and endpoint judgment. According to this standard, the content of calcium and mg ions can be accurately determined, providing key data for water quality monitoring, water treatment process optimization and equipment scale prevention maintenance.