WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
28.16 - Hydroxide and peroxide of magnesium; oxides, hydroxides and peroxides, of strontium or barium. 28 16.10 - Hydroxide and peroxide of magnesium 2816.40 - Oxides, hydroxides and peroxides, of strontium or barium (A) MAGNESIUM HYDROXIDE AND PEROXIDE (I) Ma nesium hydroxide (Mg(OH)2). White powder, heavier than magnesium oxide; stable but orming the carbonate slowly when exposed to air. Used in pharmacy. B (2) Magnesium peroxide MgOz). Prepared by the action of hydro en peroxide on ite powder, containing oxide as impurity; a most insoluble in magnesium hydroxide. water. Used for bleaching feathers, in preparing dentifrices or as a gastro-intestinal antiseptic. 6, Magnesium oxide is excluded (heading 25.19 or if in the form of cultured crystals weighing not less than 2.5 g each, heading 38.24). (B) STRONTIUM OXIDE, HYDROXIDE AND PEROXIDE (1) Strontium oxide (anhydrous or caustic strontia) (SrO). Prepared by calcining precipitated strontium carbonate. Porous white, h groscopic owder, soluble in water. Forms the carbonate when exposed to air. Use in pyrotec? xllcs I or medicine and for preparing strontium hydroxide and pigments. B (2) Strontium h droxide (Sr(OH)2). Exists in the anhydrous amorphous state or crystallised with 8 HzO; orms the carbonate when exposed to air. Used in glass manufacture, and for the preparation of strontium salts and luminous pigments. I (3) Strontium peroxide (SrOz). Prepared by the action of oxygen on strontium oxide. White powder, decomposed by hot water. Used in pyrotechnics. (C)BARIUM OXIDE, HYDROXIDE AND PEROXIDE (1) Barium oxide (anhydrous baryta) (BaO). This product must not be confused with natural barium sulphate, sometimes known as barytes. It is obtained by calcinin precipitated barium nitrate or precipitated barium carbonate, or by hydrolysing barium si ~cate.Barium oxide resembles stronttum oxide in ap earance, but is heavier (specific gravity about 5.5) and can crystallise. Used for preparing arium hydroxide and peroxide and barium metal. f g The heading excludes the crude product obtained by merely calcining witherite (heading 25.11). (2) Barium hydroxide (Ba(OH)2). Usually in the form of whitish and efflorescent lamellar Used in : the glass industry; or as an aqueous solution (baryta X-ra shtelds; in pottery; for ing water; manufacture of and o various barium compounds. ?' (3) Barium peroxide (Ba02).Prepared by heating barium oxide in air freed of carbon dioxide. White powder or insoluble greyish lumps (specific gravity about 5 . When decomposed by water it produces hydrogen peroxide; used for the manufacture of e latter.
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.