GB/T 9758.5-1988 is a Chinese national standard that specifies the determination method of hexavalent chromium content in the pigment part of liquid Paints or in powdered Paints, using diphenylcarbazide Spectrophotometric method, spectrophotometry. The standard is suitable for the determination of hexavalent chromium content in Paints and varnishes to ensure the safety and environmental friendliness of Coating products. The standard describes the experimental procedures, reagent preparation and result calculation methods in detail, emphasizing the color development process in which hexavalent chromium reacts with diphenylcarbazide to form a purplish-red complex under acidic conditions. By implementing this standard, the content of hexavalent chromium in Coatings can be effectively monitored to prevent its potential harm to the environment and human health.