This standard specifies the basic requirements, technical requirements, test methods, inspection rules, marking, packaging, transportation, storage, quality commitment and service requirements for the optical brightener APA-U. This standard applies to fluorescent whitening agent APA-U products made from raw materials such as 4,4ˊ-diaminostilbene-2,2ˊ-disulfonic acid (DSD acid) and cyanuric chloride.