This standard specifies the drying loss method for the determination of moisture in thermally stable solid chemical products. The principle involves heating the sample to drive off volatile substances, including moisture, and calculating the moisture content based on the mass loss before and after drying, thereby providing a fundamental testing approach for quality control of chemical products. The method is straightforward and intuitive. In practical testing, it typically requires an electric thermostatic drying oven capable of precisely controlling the temperature at 105°C ± 2°C, as well as a high-precision analytical balance with a readability of 0.1 mg for weighing. With technological advancements, many modern instruments, such as halogen moisture analyzers, are also widely used. These devices integrate heating and weighing units, automatically calculate and display moisture content, significantly improving testing efficiency.