GB/T 3780.5 - 2008 regulates the process of measuring the specific surface area of carbon black by the CTAB method. Specific surface area is a key characteristic of carbon black and is related to its application performance in various fields. This standard makes detailed and unified regulations on CTAB reagent preparation, sample processing, test steps and data calculation. It provides a reliable method for accurately measuring the specific surface area of carbon black for carbon black production enterprises, scientific research institutions and related application industries, which helps to accurately evaluate the carbon black mass, optimize product formulations, improve the application effect of carbon black in rubber, Coating and other industries, and promote the development of industrial standardization.