Inorganic Chemicals for Industrial Use—General Method for the Determination of Whiteness (Draft for Comments)

Applicable to the determination of whiteness of powder products among inorganic chemical products, this draft is intended for quality testing by manufacturers, users and testing institutions using whiteness meters. It specifies terms including whiteness and whiteness value, as well as technical requirements for whiteness meters, standard white plates and constant-pressure powder sample presses. Samples are required to be thoroughly mixed and prepared with a flat surface, with a recommended particle size below 180 μm, followed by instrument adjustment, sample pressing and repeat measurements. The draft specifies calculation methods and permissible differences for blue-light whiteness, Ganz whiteness and building-material whiteness, and proposes to replace GB/T 23774—2009 while tightening certain repeatability and measurement-difference requirements.