WCO Explanatory Notes reproduced for reference. © World Customs Organization. Verify against official WCO publication.
28.02 Sulphur, subiimed or precipitated; colloidal sulphur. (A) SUBLIMED OR PRECIPITATED SULPHUR The sulphur in these two categories is usually about 99.5 % pure. Sublimed sulphur, or flowers of sulphur, is obtained by slow distillation of crude or irn ure sulphur, followed by condensation m the solid form (or sublimation) as fine, very eght particles. It is chiefly used in viticulture, in the chemical industry or for vulcanising high-grade rubber. This heading also includes " washed sublimed sulphur ", treated with ammonia solution to eliminate the sulphur dioxide; this product is used in medicine. The precipitated sul hur classified here is always obtained by precipitating a solution of a sulplude, or of an alfaline or alkaline-earth 01 sulphide, with hydrochloric acid. h is more finely divided and paler yellow than sublime~sil&hur;its odour is somewhat similar to that of hydrogen sulphide and it deteriorates with age. Its uses are almost entirely medicinal. The precipitated sulphur of this heading must not be confused with certain " recovered " (triturated or micronised) sulphurs somebmes described as " preciprtated " but classified in heading 25.03. (B) COLLOIDAL SULPHUR Colloidal sulphur is obtained by the action of hydrogen sulphide on a solution of sul hur dioxide containing gelatin. It may also be obtained b the actron of mineral acid on so utn thiosulphate, or by cathodic pulverisation. Colloidal su phur is a white powder which foms an emulsion with water; however it can be preserved in this state only if a protective colloid (albumin or gelatin) is added, and even then it can be kept for only a limited time. The heading includes this prepared colloidal solution. Like all colloidal dispersions, sulphur dispersions have a large surface for adsorption and can take up colouring matter; they are also very active antiseptics used internally in medicine. I Si The heading excludes unrefined sulphur as obtained by the Frasch process and refined sulphur, even though they are often very pure (heading 25.03).
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.