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25.03 ‑ Sulphur of all kinds, other than sublimed sulphur, precipitated sulphur and colloidal sulphur.
The heading includes :(1) Crude mineral sulphur occurring in the free state, whether or not concentrated by mechanical processes to remove part of the rocky matter. (2) Unrefined sulphur extracted from mineral sulphur by melting. This process may be carried out in sulphur kilns (calcaroni), furnaces (Gill furnaces), etc., or may be effected in the deposit itself by forcing superheated steam through pipes sunk in a bore hole (Frasch process). (3) Unrefined sulphur obtained by the roasting of pyrites or by the treatment of other sulphur minerals. (4) Unrefined sulphurs recovered as by‑products in the purification of coal gas, by the scrubbing of sulphurous furnace gases, from sour natural gas and from the refining of sour crude mineral oils, etc. These recovered sulphurs, sometimes referred to as "purified sulphur"or "precipitated sulphur", must not be confused with the precipitated sulphur defined in the Explanatory Note to heading 28.02.
The unrefined sulphurs in the last three paragraphs are sometimes fairly pure. This is especially true of the sulphur produced by the Frasch process which contains such small proportions of impurities that it is practically never refined; it is usually presented in rough lumps or as dust. (5) Refined sulphur, obtained by rapidly distilling crude sulphur and condensing it in the liquid state; sulphur thus obtained can then be moulded into sticks or cakes, or crushed after solidification. (6) Triturated sulphur, which is sulphur (impure or refined) in the form of a finely divided powder obtained by grinding and then sieving, either mechanically or by gas suction. These products are known as "sieved sulphur", "winnowed sulphur", "atomised sulphur", etc., according to the process employed and the fineness of the particles. (7) Sulphur, obtained by the sudden cooling of sulphur vapours without passing through the liquid phase, which is insoluble, particularly in carbon disulphide (sulphur μ). The various types of sulphur classified in this heading are used in the chemical industry (preparation of numerous sulphur compounds, sulphur dyestuffs, etc.) for vulcanising rubber, as a fungicide in viticulture, in the manufacture of matches and sulphur wicks and for the preparation of sulphur dioxide in the bleaching industries, etc.
The heading excludes sublimed sulphur, precipitated sulphur and colloidal sulphur (heading 28.02). Sulphur put up in forms or packings for retail sale as fungicides, etc., falls in heading 38.08.
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