The classification turns on physical form at the time of importation: solid flakes, pellets, or prills are classified under 281511, while any aqueous solution — regardless of concentration — falls under 281512. Importers should confirm the product's physical state in the commercial invoice and certificate of analysis, as misclassification between these two subheadings is a common audit finding.

Sodium and potassium peroxides are strong oxidizers classified as DOT Division 5.1 hazardous materials, requiring oxidizer labeling, segregation from flammables, and emergency response documentation. They may also trigger EPA TSCA certification. Because they can react violently with water, importers should verify that packaging meets UN performance standards and that storage facilities are appropriately rated.