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).
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.