WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
28.40 Borates; peroxoborates (perborates). - Disodium tetraborate (refined borax) : 2840.1 1 - - Anhydrous 2840.19 - - Other 2840.20 2840.30 - Other borates - Peroxoborates (perborates) (A) BORATES Subject to the exclusions mentioned in the introduction to this sub-chapter, this headin covers borates, metal salts of the various boric acids, principally normal or orthoboric acid fk3E303) (heading 28.10). Borates obtained by crystallisation or by a chemical process are covered by this heading, as are also natural borates obtained by evaporating complex brines from certain salt lakes. (1) Sodium borates. The most important is the tetraborate disodium tetraborate, refined borax) (Na2B407).Obtained by crystallisation of solutions o natural borates, or by treating natural calcium borates or boric acid with sodium carbonate. Anhydrous or h drated with 5 H20or 10 H20. Heated and then cooled down, it gives a vitreous mass borax, borax glass, borax bead . Used for stiffening linen or pa er; in soldering metals (flux for hard solder); as a flux or enamels; in the manufacture o vitrifiable colours, specla1 glass (optical glass, lass for electric bulbs), glue or polish; for refining gold; and for preparing borates and an aquinone dyes. & f' belted F There are other sodium borates (metaborates, hydrogen diborate) for laboratory uses. (2) Ammonium borates. The most important of these is metaborate (NH4B02.2H20). Colourless c stals, very soluble in water, efflorescent. Decomposed by heat to give a fusible varnis of boric anhydride; hence its use as a fire-proofin material. Also used as a fixative in hair-lotions; as a component of electrolytes for electro ytic capacitors and in the coating of paper. ? f (3) Precipitated calcium borates. Obtained by treating natural borates with calcium chloride; white powder used in fire retardant compositions, in anti-freezing preparations and in ceramic insulators. It can also be used as an antiseptic. (4) Manganese borates. Mainly tetraborate (MnB407), pinkish powder, sparingly soluble. Used as a drier in paints or varnishes. (5) Nickel borate. Pale green crystals, used as a catalyst. (6) Copper borate. Blue crystals, very hard, insoluble in water. Used as a pigment (ceramic colours) and as an antiseptic and insecticide. (7) Lead borate. Greyish powder, insoluble in water. It is used to prepare driers, in glass-making, as a pigment for porcelain and in electroplating. (8) Other borates. Cadmium borate is used as a coating for fluorescent tubes. Cobalt borate is used as a drier; zinc borate as an antiseptic, in fire-proofing textiIes or as a flux in ceramics, zirconium borate as an opacifier. Natural sodium borates (kernite, tincal), used to prepare the borates of this headin ,and natural calcium borates, (pandermite, priceite), used in the manufacture of boric acid, are excluded heading 25.28). (B)PEROXOBORATES (PERBORATES) Subject to the exclusions mentioned in the introduction to this sub-Cha ter, this heading covers metal peroxoborates, which are more oxygenated than borates and readi y release their oxygen. I' The are enerally complex products the formula of which corresponds to several acids such as HB& or h o 4 . The main peroxoborates are : (1) Sodium peroxoborate (perborax). Obtained by the action of sodium peroxide on an aqueous solution of boric acid, or by treatin an aqueous solution of soQum borate with h drogen eroxide. White amorphous pow er or c stals (with 1 or 4 H20). Used for breaching inen, textiles and straw; for preserving hi es; in the manufacture of household washing preparations, detergents and antiseptics. f (2) Magnesium peroxoborate. White powder, insoluble in water, used in medicine or in the manufacture of toothpastes. (3) Potassium peroxoborate. Similar characteristics and uses to sodium peroxoborate. (4) Other peroxoborates. Ammonium, aluminium, calcium or zinc peroxoborates, which occur as white powders, are used in medicine and in the manufacture of tooth-pastes.
Notes. 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. 2.- In addition to dithionites and sulphoxylates, stabilised with organic substances (heading 28.31), carbonates and peroxocarbonates of inorganic bases (heading 28.36), cyanides, cyanide oxides and complex cyanides of inorganic bases (heading 28.37), fulminates, cyanates and thiocyanates, of inorganic bases (heading 28.42), organic products included in heading 28.43 to 28.46 and 28.52 and carbides (heading 28.49), only the following compounds of carbon are to be classified in this Chapter : (a) Oxides of carbon, hydrogen cyanide and fulminic, isocyanic, thiocyanic and other simple or complex cyanogen acids (heading 28.11); (b) Halide oxides of carbon (heading 28.12); (c) Carbon disulphide (heading 28.13); (d) Thiocarbonates, selenocarbonates, tellurocarbonates, selenocyanates, tellurocyanates, tetrathiocyanatodiamminochromates (reineckates) and other complex cyanates, of inorganic bases (heading 28.42); (e) Hydrogen peroxide, solidified with urea (heading 28.47), carbon oxysulphide, thiocarbonyl halides, cyanogen, cyanogen halides and cyanamide and its metal derivatives (heading 28.53) other than calcium cyanamide, whether or not pure (Chapter 31). 3.- Subject to the provisions of Note 1 to Section VI, this Chapter does not cover : (a) Sodium chloride or magnesium oxide, whether or not pure, or other products of Section V; (b) Organo-inorganic compounds other than those mentioned in Note 2 above; (c) Products mentioned in Note 2, 3, 4 or 5 to Chapter 31; (d) Inorganic products of a kind used as luminophores, of heading 32.06; glass frit and other glass in the form of powder, granules or flakes, of heading 32.07; (e) Artificial graphite (heading 38.01); products put up as charges for fire-extinguishers or put up in fire- extinguishing grenades, of heading 38.13; ink removers put up in packings for retail sale, of heading 38.24; cultured crystals (other than optical elements) weighing not less than 2.5 g each, of the halides of the alkali or alkaline-earth metals, of heading 38.24; (f) Precious or semi-precious stones (natural, synthetic or reconstructed) or dust or powder of such stones (headings 71.02 to 71.05), or precious metals or precious metal alloys of Chapter 71; (g) The metals, whether or not pure, metal alloys or cermets, including sintered metal carbides (metal carbides sintered with a metal), of Section XV; or (h) Optical elements, for example, of the halides of the alkali or alkaline-earth metals (heading 90.01). 4.- Chemically defined complex acids consisting of a non-metal acid of sub-Chapter II and a metal acid of sub-Chapter IV are to be classified in heading 28.11. 5.- Headings 28.26 to 28.42 apply only to metal or ammonium salts or peroxysalts. Except where the context otherwise requires, double or complex salts are to be classified in heading 28.42. 6.- Heading 28.44 applies only to : (a) Technetium (atomic No. 43), promethium (atomic No. 61), polonium (atomic No. 84) and all elements with an atomic number greater than 84; (b) Natural or artificial radioactive isotopes (including those of the precious metals or of the base metals of Sections XIV and XV), whether or not mixed together; (c) Compounds, inorganic or organic, of these elements or isotopes, whether or not chemically defined, whether or not mixed together; (d) Alloys, dispersions (including cermets), ceramic products and mixtures containing these elements or isotopes or inorganic or organic compounds thereof and having a specific radioactivity exceeding 74 Bq/g (0.002 μCi/g); (e) Spent (irradiated) fuel elements (cartridges) of nuclear reactors; (f) Radioactive residues whether or not usable. The term “isotopes”, for the purposes of this Note and of the wording of headings 28.44 and 28.45, refers to : - individual nuclides, excluding, however, those existing in nature in the monoisotopic state; - mixtures of isotopes of one and the same element, enriched in one or several of the said isotopes, that is, elements of which the natural isotopic composition has been artificially modified. 7.- Heading 28.53 includes copper phosphide (phosphor copper) containing more than 15 % by weight of phosphorus. 8.- Chemical elements (for example, silicon and selenium) doped for use in electronics are to be classified in this Chapter, provided that they are in forms unworked as drawn, or in the form of cylinders or rods. When cut in the form of discs, wafers or similar forms, they fall in heading 38.18. Subheading Note. 1.- For the purposes of subheading 2852.10, the expression “chemically defined” means all organic or inorganic compounds of mercury meeting the requirements of paragraphs (a) to (e) of Note 1 to Chapter 28 or paragraphs (a) to (h) of Note 1 to Chapter 29.