This is a national standard method for determining the whiteness of edible salt and industrial salt in the salt industry. The method objectively evaluates the whiteness value by measuring the spectral reflectance factor of salt samples under specific blue light conditions at a given wavelength. During the detection process, measurements must be performed using a specialized whiteness meter (such as the WSB-3 model mentioned in some references) with a spectral response condition of an effective wavelength of 457 nanometers and a half-wave width of 44 nanometers, in accordance with JJG 512 "Verification Regulation of Whiteness Meters." To ensure the reliability of the measurement results, the standard also clearly specifies the permissible error for parallel determinations of the same sample.