GB/T 5211.3-2020 "General methods of test for pigments and extenders - Part 3: Determination of matter volatile at 105°C" applies to pigments and extenders and specifies the procedure for determining the content of matter volatile at 105°C. A specified amount of the sample is weighed and dried in an oven at 105±2°C until constant mass is achieved. The mass fraction of volatile matter is calculated based on the difference in mass before and after drying. The standard specifies requirements for balance accuracy, sample quantity, and drying time. The absolute difference between parallel test results must comply with the corresponding accuracy requirements to ensure the accuracy and comparability of the determination of volatile matter content.