WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
28.08 - Nitric acid; sulphonitric acids. (A) NITRIC ACID Nitric acid (HN03) is m a d obtained by oxidising ammonia in the presence of a catalyst (platinum, iron, chromium, %smuth or manganese oxides, etc.). Alternatively, nitrogen and oxy en may be directly combined in an electric-arc furnace and the resultmg nitnc oxide 0x1 ised. It can also be prepared by the action of sulphuric acid (alone or associated with sodium disul hate) on natural sodium nitrate; the impurities (sulphulric or hydrochloric acids, nitrous fume6 are eliminated by distillation and hot air. Nitric acid is a colourless or yellowish toxic liquid. h concentrated form (fiuning nitric acid), it gives off clouds of yellowish nitrous fumes. It attacks the skin and destroys organic matter; ~tis a powerful oxidising agent. It is presented in glass or earthenware carboys or aluminium containers. Its uses include the manufacture of nitrates (of silver, mercury, lead, copper, etc. organic dyes, explosives (nitroglycerol, collodion cotton, trinitrotoluene, picric acid, mercury lminate, etc.); the pickling of metals (especially for pickling cast iron); copperplate engraving; gold or silver refining. (B) SULPHONITRIC ACIDS Sul honitric acids are mixtures in definite proportions (e.g., equal parts) of concentrated nitric an sulphuric acids. They are highly corrosive, viscous liquids, generally presented in sheet-iron drums. They are used, in particular, for nitrating organic compounds in the synthetic dyestuffs industry, and in the manufacture of nitrocellulose and explosives. The heading does not cover : (a) Arninosulphonic acid (sulphamic acid) (heading 28.11) (not to be confused with the sulphonitric acids above). (b) Hydrogen azide, nitrous acid and the various oxides of nitrogen (also heading 28.11).
1.- Except where the context otherwise requires, the headings of this Chapter apply only to : (a) Separate chemical elements and separate chemically defined compounds, whether or not containing impurities; (b) The products mentioned in (a) above dissolved in water; (c) The products mentioned in (a) above dissolved in other solvents provided that the solution constitutes a normal and necessary method of putting up these products adopted solely for reasons of safety or for transport and that the solvent does not render the product particularly suitable for specific use rather than for general use; (d) The products mentioned in (a), (b) or (c) above with an added stabiliser (including an anti-caking agent) necessary for their preservation or transport; (e) The products mentioned in (a), (b), (c) or (d) above with an added anti-dusting agent or a colouring substance added to facilitate their identification or for safety reasons, provided that the additions do not render the product particularly suitable for specific use rather than for general use.