WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
28.13 - Sulphides of non-metals; commercial phosphorus trisulphide. 28 13.10 2813.90 - Carbon disulphide - Other The most important of these binary compounds are : (1) Carbon disulphide (CS2). Results fiom the action of sulphur vapours on burning carbon. Colourless, toxic liquid (specific gravity about 1.3). Not miscible with water. Smells of rotten e gs when impure. Very volatile and highly inflammable, it is dangerous to inhale an to handle. It is presented in stoneware, metal or glass containers encased in straw or osier, and very tightly stoppered. f It is used as a solvent for numerous pu oses, e.g., for extracting oils, fats or essential oils, for defatting bones, in medicine, or in e man-made textile or rubber industries. It is also used in a culture where it is in'ected into the soil for destroying insects, ihylloxera, etc. For the atter use, the derive product potassium thiocarbonate (hea ing 28.42) is sometimes used. (See the Explanatory Note to heading 38.08.) % F d (2) Silicon disulphide (SiS2). Obtained by the action of sulphur vapour on strongly heated silicon. White solid; crystallises in volatile needles. Decomposes water with formation of gelatinous silica. (3) Arsenic sulphides. This heading covers artificial sulphides obtained either from natural sulphides, or from arsenic or arsenous oxide by treatment with sulphur or hydrogen sulphide. (a) Diarsenic disulphide (artificial redgar, false realgar, red sulphide) (As2S2or As4S4). Toxic roduct, occurring in vitreous red or orange-coloured crystals, specific about 9.5. Volatilises wthout melting. Used for the manufacture of fireworks with potassium nitrate and sulphur), In paints (ruby arsenic), or in leather dressing for dehalring hides. Kc (b) Diarsenic trisulphide (artificial orpiment, false auripi ment, yellow sul hide) (AS&). Toxic yellow powder, specific gravity about 2.7; o ourless and inso uble in water. Similar uses to the disulphide, and also as a pi ent for leather or rubber, as a parasiticide or in medicine (because it destroys mor id growths). With alkali sulphides, it forms thioarsenites of heading 28.42. f 'f iY (c) Diarsenic pentasul hide (As2S5).This product, which does not occur in nature, is a light yellow amorp ous solid, insoluble in water. Used as a pigment. With alkali sulph~des,it also forms thioarsenates of heading 28.42. The headin excludes natural arsenic sulphides (disulphide or realgar, trisulphide or orpiment) (heading 2830). (4) Phosphorus sulphides. (a) Tetraphosphorus trisulphide (P4S3).Obtained fiom the constituent elements. Grey or yellow solid. Specific avity of about 2.1. Occurs either as an amo hous mass or in c stals. Smells of gar IC and is not very toxic, though the dust is rat er dangerous to s a l e . It is d e c o ~ o s e d by boiling water, but is not affected by sir.It is the most stable phosphorus sul hde. Used in the manufacture of the pentasulphide, and in place of phosphorus in t e manufacture of safety matches; also in organic synthesis. P T (b) Diphosphorus pentasulphide (P2S5 or P~SI~). OCCUTS in yellow crystals; specific avity 2.03 to 2.09. Used for the same purposes as tetraphosphorus tnsulphide or for t e preparation of flotation agents for ores. TI (c) Commercial phosphorus trisulphide. The product known as phosphorus trisulphide is a mixture whose formula approximates to PS3; it occurs in yellowish grey crystalline masses, decomposed by water. Used in organic synthesis. The heading excludes : (a) The binary combinations of sulphur with halogens (e.g., sulphur chlorides) (heading 28.12). (b) Oxysulphides (e-g., of arsenic, carbon and silicon), and the thiohalides of non-metals (e.g., phosphorus chlorosulphideand thiocarbonyl chloride) (heading 28.53). Sub-chapter IV INORGANIC BASES AND OXIDES, HYDROXIDES AND PEROXIDES OF METAL GENERAL Bases are com ounds characterised by a hydroxyl radical OH) and which react with acids to form salts. In t e liquid state or in solution, they are electro ytes giving a metal or an analogous ion (ammonium (NH,')) at the cathode. I !i Metal oxides are com ounds of a metal with oxygen. Many can combine with one or more molecules of water to o m hydroxides. ? Most oxides are basic since their hydroxides act as bases. Certain oxides (anhydride oxides), however, react only with alkaline or other bases to form salts, while another more common class (amphoteric oxides) can behave both as anh dride oxides or as bases. These classes of oxides must be regarded as anhydrides of aci s, real or hypothetical, corresponding to their hydroxides. B Certain oxides (saline oxides) may be regarded as resulting from the combination of a basic oxide with an anhydride oxide. This sub-chapter covers (1) Oxides, hydroxides and peroxides of metal, whether basic, acidic, arnphoteric or saline. (2) Other inor anic bases containing no oxygen, such as ammonia (heading 28.14), or hydrazine (heading 2 .25), and those containing no metal, such as hydroxylamine (heading 28.25). f The sub-chapter excludes : (a) The oxides and hydroxides of Chapter 25, particularly magnesia (magnesium oxide), whether or not pure, and quicklime and slaked lime (crude calcium oxide and hydroxide). I (b) Oxides and h droxides constituting ores headings 26.01 to 26.17), scalings, ash, slag, dross, scum or other metaziferous residues (headings 6.18 to 26.20). (c) Oxides, peroxides and hydroxides of precious metals (heading 28.43 , of radioactive elements heading 28.44), of rare-earth metals, of yttrium or of scandium or o mixtures of these metals heading 28.46), or of mercury (heading 28.52). (d) Oxy en compounds of hydrogen of headin 22.01 (n-ater), heading 28.45 (heavy water), heading
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.