This standard specifies methods for the determination of residual chlorine and free chlorine in industrial cycle chilled down water and raw water, with a determination range of 0.03 mg/L to 2.5 mg/L. This standard applies to the analysis of residual chlorine in industrial cycle chilled down water, replacing the GB/T 14424-1993 version. Compared with the previous version, this standard eliminates DPD visual Colorimetry and o-dimethylaniline visual Colorimetry, and expands the measurement range to apply to a wider range of industrial water treatment applications.