WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
28.07 - Sulphuric acid; oleum. (A) SULPHURTC ACID Sulphuric acid (H2S04)is mainly obtained by passing oxygen and sulphur dioxide over a catalyst (platinum, ferric oxide, vanadium pentoxlde, etc.). It is freed from impurities (nitrogen corn ounds, arsenical or seleniferous products, lead sulphate) by treatment with hydrogen sulpkde or ammonium sulphide. Sulphuric acid is a very strong corrosive. It is a dense, oily liquid, colourless (if it does not contain impurities or yellow or brown (in other cases). It reacts violently on contact with water and destroys the s 'n and most organic substances by carbonising them. rb Commercial sulphuric acid contains between 77 and 100 % H2S04.It is presented in containers or carboys of glass, in steel drums, tank trucks, railway tank wagons or tank ships. This acid is used in a great number of industries : it is used in particular in the preparation of fertilisers, explosives and inorganic pigments and, inter alia, in the petroleum and steel xndustsies. (B)OLEUM Oleum (fuming sulphuric acid) is sul huric acid charged with an excess (up to 80 %) of sulphur trioxide. Oleums can be liquid or soEd, very bmwn m colour; they react violent1 with water, attack the skin and clothing, give off dangerous fumes (in particular, free sulp ur trioxide). They are presented in glass, earthenware or sheet iron containers. i Oleurn is largely used in sulphonation reactions in organic chemistry (preparation of naphthalenesulphonic acid, hydroxyanthraquinone, thioindigo, alizarin derivatives, etc.). The heading does not include : (a) Chlorosul huric acid (" sulphuric chlorohydrin ") and sulphonitric acid (beadings 28.06 and 28.08, respective y). P @) Sulphur trioxide, hydrogen sulphide, peroxosulphuric (persulphuric acids, sulphamic acid and the mineral acids of the thionic series (polythionic acids) (heading 28.11 (c) Thionyl ox sulphuryl chlorides (heading 28.12).
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.