WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
28.05 Alkali or alkalineearth metals; rare-earth metals, scandium and yttrium, whether or not intermixed or interalloyed; mercury. - Alkali or alkaline-earth metals : - - Sodium 2805.12 - - Calcium 2805.19 - - Other 2805.30 - Rare-earth metals, scandium and yttrium whether or not intermixed or 2805.11 interalloyed 2805.40 - Mercury (A) ALKALI METALS The five alkali metals are soft and rather light. They decompose cold water; they deteriorate in air, forming hydroxides. (I) Lithium. This is the lightest (specific gravity 0.54) and hardest of the group. It is kept in mineral oil or inert gases. Lithium helps to improve the ualities of metals, and is used in various alloys (e.g., anti-fiiction alloys). Because of its great a lnity for other elements, it is also used, inter alia, to obtain other metals in the pure state. b (2) Sodium. A solid (specific gravity 0.97) with a metallic lustre, readily tarnishing after cutting. It is preserved in mineral oil or in airtight welded tins. Sodium is obtained by electrolysing molten sodium chloride or sodium hydroxide. It is used in the manufacture of sodium peroxide (" dioxide "), sodium cyanide, sodamide, etc., the indigo industry, the manufacture of explosives (chemical primers and fuses), the polymerisation of butadiene, anti-fiction alloys, or titanium or zirconium metallurgy. The heading excludes sodium amalgam (heading 28.53). (3) Potassium. A silvery-white metal (specific gravity 0.85), which can be cut with an ordinary knife. It is preserved in mineral oil or in sealed ampoules. Potassium is used for the preparation of certain photoelectric cells, and in anti-friction alloys. (4) Rubidium. A silvery-white solid specific gravity 1.5), more fusible than sodium. It is preserved in sealed ampoules or in minera oil. I Like sodium, it is employed in anti-fi-iction alloys. ( 5 ) Caesium. A silvery-white or yellowish metal (specific avity 1.9 , which ignites on contact with air; the most readily oxidislng metal; presented in sea ed ampou es or in mneral oil. Y The radioactive alkali metal ffancium is excluded (heading 28.44). (B) ALKALINE-EARTH METALS The three alkaline-earth metals are malleable and decompose cold water fairly readily; they deteriorate in damp air. (1) Calcium. Obtained by the alumino thermal reduction of calcium oxide or by electrolysing molten calcium chloride. It is a white metal (specific gravity 1.57), used in the urification of argon, the refining of copper or steel, the manufacture of zirconium, calcium ydride (hydrolith), anti-friction alloys, etc. R (2) Strontium. White or pale yellow metal, ductile (specific gravity 2.5). (3) Barium. White metal (specific gravity 4.2); used in certain anti-friction alloys and in the preparation of getters for vacuum tubes (heading 38.24). This heading does not include radium, a radioactive element (heading 28.44), magnesium (heading 81.04), or beryllium (heading 81.12); these all resemble alkaline-earth metals in certain respects. (C) RARE-EARTH METALS; SCANDIUM AND YTTRIUM, WHETHER OR NOT INTERMIXED OR INTERALLOYED Rare-earth metals (the term " rare-earth " ap lies to their oxides) or lanthanons comprise the elements with atomic numbers (*) fran 57 to 71 in the periodic system, i.e. : Cerium group Terbium group Erbium group 63 Europium 64 Gadolinium 65 Terbium Lanthanum Cerium Praseodymium Neodymium Samarium Dysprosium Holmium Erbium Thulium Ytterbium 71 Lutetium Promethium (element 61), which is radioactive, is classified in heading 28.44. The rare-earth metals are generally greyish or yellowish, and ductile or malleable. (*) The atomic number of an element is the total number of orbital electrons contained in an atom of that element. Cerium, the most important of the group, is obtained fiom monazite (rare-earth phos hate) or thorite (rare-earth silicate), after the removal of thorium. Cerium is obtained b metal otherrnic reduction of the halides using calcium or lithium as the reductant or by electro ysis of the fused chloride. It is a grey ductile metal, a little harder than lead, and gives off sparks when rubbed on rough surfaces. r f Lanthanum, which exists in the impure state in ceric salts, is used in the manufacture of blue glass. This heading also covers scandium and yttrium which resemble the rare-earth metals quite closely - scandium in addition resembles the metals of the iron group. These two metals are extracted from the ore thortveitite, a silicate of scandium containing yttrium and other elements. These elements remain classified here whether or not intermixed or interalloyed. For instance, the heading covers " Mischmetal ", which is an alloy containing 45 to 55 % cerium, 22 to 27 % lanthanum, other lanthanons, yttrium and various impurities (up to 5 % iron, traces of silicon, calcium, aluminium). " Mischmetal " is used mainly in metallurgy and for the manufacture of li hter flints. When alloyed with more than 5 % iron or with magnesium or other metals it falls e sewhere (e.g., if it has the character of a pyrophoric alloy, in heading 36.06). k The heading excludes the salts and compounds of rare-earth metals, of yttrium and of scandium (heading 28.46). (D) MERCURY Mercury (quicksilver) is the only metal which is liquid at room temperature. It is obtained by roasting natural mercury sulphide (cinnabar) and is separated from the other metals contained in the ore (lead, zinc, tin, bismuth) by filtration, distillation in a vacuum, and treatment with dilute nitric acid. is a very brilliant silver-coloured liquid, heavy (specific gravity 13.59), toxic and liable to attac precious metals. At room temperature, pure mercury is unaffected by exposure to air, but the impure metal takes on a coating of brownish mercuric oxide. Mercury is presented in special iron containers (" flasks "). Mercury is used for preparing the amalgams of heading 28.43 or 28.53. It is used in old or silver metalluro, in the gold- or silver- lating industries, and in the manufacture of c orine, sodium hydroxide, mercury salts, verrniEon or fulminates. It is also used for making mercury vapour lamps and in various physical instruments, in medicine, etc. Sub-chapter I1 INORGANIC ACIDS AND INORGANIC OXYGEN COMPOUNDS OF NON-METALS GENERAL r Acids contain hydrogen which can be wholly or artly replaced b metals (or by ions with analogous pro erties, e.g., the ammonium ion @I& as) a)result sa ts are formed. Acids react with bases to o m salts, and with alcohols to form esters. In the liquid state or in solution, they are electrolytes which produce hydrogen at the cathode. When one or more molecules of water are eliminated fiom those acids containing oxygen, anhydrides are obtained. Most oxides of non-metals are anhydrides. P This sub-chapter covers inorganic oxygen compounds of non-metals (anhydrides and other), and also inorganic acids, the anode radical of which is a nonmetal. On the other hand it excludes anhydrides and acids formed, respectively, by metal oxides or hydroxides; these general1 fall in sub-Cha ter TV (e.g., metal oxides, hydroxides and peroxides, such as acids or anhydrides ofYchmmium, moly denum, tun sten and vanadium). In certain cases, however, they fall elsewhere, e.g., in heading 28.43 (cornpounfs af reciow metals), heading 28.44 or 28.45 (corn ounds of radioactive elements and isotopes) or beading 48.46 (compounds of rare-earth metals, of scanBum or yttrium). Oxygen corn ounds of hydrogen are also excluded and are classified under heading 22.01 (water), heading 28.& (hea water), heeding 28.47 hydrogen peroxide) or headin 28.53 (distilled and conduct~vitywater mywater of s~rnllarpurity, inc uding water treated with ion-exc ange media). \
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.