WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
28.30 - Sulphides; polysulphides,whether or not chemically defmed. 2830.10 - Sodium sulphides 2830.90 - Other Subject to the exclusions mentioned in the introduction of this sub-chapter, this headin covers metal sulphides (salts of hydrogen sulphide (HZS) of headmg 28.11). 2he old name " sulphydrates " (hydrosulphides) is sometimes applied to the acid sulphides. Sulphides of non-metals are excluded (heading 28.13). (1) Sodium sulphides. (a) Sodium sulphide F a z S . Prepared by reducing sodium sulphate by means of coal. Either anhydrous, m w 'tish masses or plates (concentrated or melted sulphide), soluble in water, sulphating in the air, or in hydrated crystals (with 9 HzO), colourless or greenish, accordlug to their de ee of purity. Mild reducing agent used in the preparation of organic corn 0 u n d s . s flotation processes, this sulph~depromotes the absorption of oil on the sur ace of ores by sulpbiding. Also used as a hair-remover (in tanning or in toilet preparations), and as a parasiticide. I F (NaHS). Obtained by the action of hydmgen sulphide on the neutral sulphid)e. Colourless c stals, soluble in water. Used as a de-hairing agent in tanning, in-dyeing, as a copper a sorbent in nickel refining, as a reducing agent tn organic synthesis, etc. @) Sodium hydrogen sulphide (hydrosul hide) (2) Zinc sulphide (ZnS). Artificial zinc sulphide is obtained in the hydrated form by precipitating an alkali zincate by means of sodium sul hide. White paste or powder often containing zinc oxide or other impurities. It is used, eit er pure or mxed with ma esia, as a pigment in the rubber industry. Co-precipitated with barium sulphate it forms thop pone (heading 32.06). Activated with silver, copper, etc., it gives a luminophore of heading 32.06. It should, however, be noted that zinc sulphide is classified in this heading only when unmixed and non-activated. R f=' The heading excludes zinc blende a natural zinc sulphide) (heading 26.08), and m i t e (also a natural zinc sulphide) (heading 25. 0). The artificial sulphide is obtained by precipitation from a solution by hydrogen sulphide or an alkali sulphide. Yellow artists and in the manufacture of anti-glare hate, it forms the bright yellow colouring matter emp oyeci (3) Cadmium pass The heading excludes natural cadmium sulphide (greenockite) (heading 25.30). (4) Ammonium hydrogen sulphide (ammonium hydrosulphide) (N&.HS). Crystalline flakes or needles; very volatile. Used in photography and in organic synthesis. (5) Calcium sulphide (CaS). Obtained by calcining a mixture of calcium sulphate and carbon, Greyish or yellowish masses, sometimes lurmnescent, almost insoluble in water. Often contains sul hate or other impurities. Used either alone, or treated with arsenous oxide or with lime or de-hairing hides. Used also as a hair-remover in toilet preparations, as a microbicide in medicine, in metallurgy and in the preparation of luminescent paints. ? (6) Iron sul hides. The most important artificial iron sulphide is the ferrous sul hide (FeS) obtained y fusion of a mixture of sulphur and iron filings. Blackish plates, stic s or lumps, with a metallic glint. Used in the manufacture of hydrogen sulphide and in ceramics. P \ Natural iron sulphides are excluded - see heading 25.02 (unroasted p tes), or 71.03 or 71.05 (marcasite). Natural double sulphides of iron with arsenic (rnisplc el) or copper (bomite, chalcopyrite) fall in headings 25.30 and 26.03, respectively. P (7) Strontium sulphide (SrS). Greyish product, turning yellow on contact with air. Used as a hair-remover in the tanning industry, in cosmetic products and in the preparation of luminescent paints. (8) Tin sulphides. Artificial stannic sulphide (tin disdphide) (SnS2) is obtained by heating a mixture of sul hur and ammonium chloride with a tin oxide or amal am. Golden yellow flakes or pow er, insoluble in water and subliming when heated. ~secfforbronzing wood, plaster, etc. F' (9) Antimony sulphides. (a) Artificial trisulphide (Sb2S3).The action of an acid on the natural sulphide dissolved in sodium hydroxide gives a red or orange-coloured owder recipitated trisulphide). Used either alone or mixed with entasulphlde or o er pro ucts as a pigment in the rubber industry (antimony v e m ion, antimony crimson). Melted natural sulphide gives black trisulphide, employed in pyrotechnics, in the manufacture of match head mixtures, of fulminating primers or caps (with otassium chlorate), of flashlight powder for photo aphy (with potassium chromate?, etc. Hot treatment with sodium carbonate gives " $ermes mineral ", consisting essential1 of antimony trisulphide and sodium pyro-antimonate and used in medicine (heading 8.24). ? d" & f @) Pentasulphide (golden a solution of antimony sochum sulphide in course of bme, even in the colouring rubber, and in medicaments for human (expectorant) or veterinary uses. Natural antimony sulphide (stibnite) and oxysulphide (kermesite) are excluded (heading 26.17). (10) Barium sulphide (Bas . Obtained by reducing the natural sulphate (b es, heading 25.1 1) b means of coa . White powder or lumps when pure, greyish or ye lowish when impure. qoxic. Similar uses to strontium sulphide. T (11) Other sulphides. These include : (a) Potassium sul hides (neutral and acid). Potassium hydrogen sulphide is used in the manufacture o mercaptans. F (b) Copper sulphides, used in the preparation of electrodes or of paints resisting the acbon of sea water; natural copper sulphide (covellite, chalcocite) is excluded (heading 26.03). (c) Lead sul hide, used in ceramics; natural lead sulphide (galena) is excluded (heading 6.07). P sulphide (cinnabar, natural vermilion) and artificial mercury sulphides are Natural merc excluded a n d 3 1in headings 26.17 and 28.52, respectively. (12) Polysulphides which are also classified here, are mixtures of sulphides of the same metal. r (a) Sodium polysulphide is obtained b heating sulphur with sodium carbonate or neutral sodium sulphide. Contains main y sodium disulphide (Na2S2), trisulphide and tetrasulphide and impurities (sulphate, sulphite, etc.). It occurs in greenish plates, soluble, oxidising in the air and very hygroscopic; it is ke t in well-stoppered containers. Used mainly as a reducing agent in organic s t esis reparabon of sulphur dyes); in flotation processes; in the preparation of e g l e n e popsulphider, of arhficial mercury sulphide, sulphur baths or mixtures for the treatment o scabies R (b) Potassium olysulphide (" liver of sulphur ") is used for the same purposes as sodium polysulphic?e and more particularly for sulphur baths. The heading also excludes the following natural sulphides : (a) Nickel sulphide (rnillerite) (heading 25.30). (b) Molybdenum sulphide (molybdenite) (heading 26.13). (c) Vanadium sulphide (patronite) (heading 26.15). (d) Bismuth sulphide (bismuthinite) (heading 26.17).
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.