This standard specifies the requirements, sampling, test methods, inspection rules, signs, labels, packaging, transportation and storage of optical brightener 351 (CI optical brightener 351) products. This standard applies to product quality control of fluorescent whitening agent 351. Structural formula: Molecular formula: CHNaOS Relative molecular mass: 562.56 (according to the 2007 international relative atomic mass) CAS RN: 27344-41-8