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28.37 - Cyanides, cyanide oxides and complex cyanides. - Cyanides and cyanide oxides : 2837.11 - - Of sodium 2837.19 2837.20 - - Other - Complex cyanides Subject to the exclusions mentioned in the introduction to this sub-chapter, this heading covers cyanides, cyanide oxides (oxycyanides) and complex cyanides. (A) CYANIDES Cyanides are the metal salts of hydrogen cyanide (HCN) (heading 28.11). These salts are very poisonous. (1) Sodium cyanide (NaCN). Obtained by the action of coke or hydrocarbon gases and atmosphenc nitro en on sodium carbonate, by treating calclum cyanamide (see heading 31.02) wi charcoal or by the interaction of pulverised coal, sodium and gaseous ammonia. White powder, plates or aste, crystalline, hygroscopic, very soluble in water and with an odour of bitter almonds.%henen brought to the melting-point it absorbs oxy en; may also give hydrates. Is presented in sealed vessels. Used in the metallurgy of go1 or silver, in gold- or silver lating, in photography, in lithography, as a parasiticide or insecticide, etc. Also use in the preparation of hydrogen cyanide, other cyanides and indigo; in flotation processes (in particular for separating galena from blende and pyrites from chalcopyrite). f (2) Potassium cyanide KCN). Obtained by similar methods, has similar characteristics and uses to sodium cyani e. (3) Calcium cyanide (Ca(CN)Z). White or greyish powder according to its degree of purity, soluble in water. Used for destroying insects, fungus and noxious animals. (4) Nickel c snide (Ni(CW2). Hydrated, greenish plates or powder; amorphous, a yellow powder. sed in metallurgy and in electroplating. (5) Copper cyanides. (a) Cuprous cyanide (CuCN). White or greyish powder, insoluble in water. Used for the same purposes as cupric cyanide and in medicine. (b) Cupric cyanide (Cu(CW2).Amorphous powder, insoluble in water, easily decomposed. Used for plating iron with copper and in organic synthesis. (6) Zinc cyanide (ZII(CN)~).White powder, insoluble in water, used in electroplating. The heading excludes c anides of mercury (heading 28.52) and cyanides of non-metals, such as bromine cyanide (beading 28.53r (B)HEXACYANOFERRATES (IT.)(FERROCYANIDES) are the metal salts of hydrogen hexacyanoferrate (11) fiom spent oxide treated with calcium hydroxide or hydroxide on cyanides. Decomposed by heat. The most important are : (1) Tetrammonium hexacyanoferrate ((NH&Fe(CV6). CrystaIs soluble in water. Used for " black nickel-plating " and as a catalyst in the synthesis of ammonia. (2) Tetrasodium hexacyanoferrate (NZI~F~(CN)~.~OH~O), Yellow crystals, d e c t e d by air, soluble in water, especially when hot. Used for preparing hydrogen cyanide and Prussian blue, thio-indigo, etc.; to case-harden steel; in photogra hy; in dyeing (as a mordant or as a blue tint); in printing (as an oxidising agent in aniline b ack printing) and as a fungicide. P (3) Tetrapotassium hexac anoferrate (&Fe(CN)6.3H20). Yellow crystals, efflorescent, soluble in water, especia ly when hot. Same uses as tetrasodium hexacyanoferrate. i (4) Dicopper hexacyanoferrate (CQF~(CN)~.XH~O). Purplis brown powder, insoluble in water. Used for preparing Florentine or Van Dyck brown for artists' paints. (5) Double hexac anoferrates Ll2K2pe(m6).3 20). k (e.g., dilithium dipotassium hexacyanofmate The heading excludes Prussian blue (Berlin blue) and other pigments based on hexacyanoferrates (heading 32.06). (C)HEXACYANOFERRATES (III) (FERRICYANIDES) Hexac anoferrates (111) (ferricyanides) are the salts of hydrogen hexacyanoferrate (ID) (H&&N)~) (heading 28.1 1). The most important are : (1) Trisodium hexacyanoferrate hexacyanoferrates (11); aqueous solution it is photography; for synthesis. by the action of chlorine on soluble in water and toxic; in in dyeing and printing; in oxidising agent in organic (2) Tripotassium hexacyanoferrate (K3Fe(CN)6). Similar appearance to trisodium hexacyano- ferrates but less deliquescent. Same uses. (D) OTHER COMPOUNDS These include pentacyanonitrosylferrates (11), pentacyanonitrosylferrates (III), cyanocadmates, cyanochromates, . . cyanomanganates, cyanocobaltates, cyanoniccolates, cyanocuprates, etc., of inorganic bases. entacyanonitrosylferrate (111) (sodium This grou includes, for example, nitroprussi e or sodium woferricyanide)sodium (Na2Fe(cp N)5N0.2H20),used in chemical analysis. S Cyanomercurates are, however, excluded (heading 28.52).
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.