The US schedule splits bismuth at the 99.99% purity level: material at or above this threshold classifies under 810610, while lower-purity bismuth and scrap fall under 810690. Purity is verified by the supplier's certified chemical analysis (typically ICP-OES or fire assay), which should accompany the commercial invoice. CBP may request laboratory testing if documentation is insufficient.

The primary end uses for 99.99%+ bismuth include pharmaceutical active ingredients (bismuth subsalicylate and related compounds), semiconductor manufacturing as a dopant, and specialty fusible alloys used in fire-suppression systems and precision casting. These applications require tight impurity controls that lower-grade bismuth cannot meet, which is why the purity distinction carries commercial and regulatory significance.