Explanatory notes
… kept in silver flasks. Its uses include etching on glass, manufacturing ashless filter paper, preparation of tantalum, … e.g., in aqueous solutions obtained as by‑products in the manufacture of superphosphates, or from silicon fluorides. … unstable, with explosive properties. Its salts (azides) fall in heading 28.50 , and not in sub‑Chapter V. (2) …