Iodine

28.01 - Fluorine, chlorine, bromine and iodine. 2801.10 - Chlorine 280 1.30 - Fluorine; bromine This heading covers the non-metals known as halogens, with the exception of astatine (heading 28.44). (A) FLUORINE Fluorine is a faintly greenish-yellow as with a pungent odour; it is clan erous to inhale as it irritates the mucous membranes an is corrostve. It is presented un er ressure in steel containers; it is a very active element which ignites organic matter - m particu ar wood, fats and textiles. d f Fluorine is used for the preparation of certain fluorides and organo-fluorine derivatives. (B) CHLORINE Chlorine is usually obtained by electrolysis of alkali chlorides, especially sodium chloride. Chlorine is a greenish-yellow gas, suffocatin ,corrosive, two and a half times as dense as air, sli tly soluble in water and readily litquefief It is usually transported in steel cylinders, tanks, rai way tank wagons or barges. p Chlorine destroys colouring and organic matter. It is used for bleachin vegetable (but not animal) fibres, and in the preparation of wood pulp. Because of its disin ecting and antiseptic properties, it is also used for sterilising (chlorinating) water. It is used in gold, fin and cadrmum metallurgy, in the manufacture of hypochlorites, metal chlorides and carbonyl chloride, in organic syntheses (e.g., synthetic dyes, artificial waxes, chlorinated rubber). f (C) BROMINE Bromine can be obtained by the action of chlorine on the alkaline bromides contained in saline mother-liquors, or by electrolysing bromides. It is a very dense (3.18 at 0 OC), corrosive, reddish or dark brown liquid which, even when cold, gves off suffocating red fumes irritating to the eyes. It inflames the skin, turning it yellow, and tes organic substances such as sawdust. It is presented in glass or pottery containers. It is s ightly soluble in water. The heading excludes solutions of bromine in acetic acid '$ (headmg 38.24). It is used in the manufacture of medicaments (e.g., sedatives), dyes (e.g., eosins, brominated derivatives of indigo), hotographic chemicals (silver bromide), lachrymatory products (bromo-acetone), in metal urgy, etc. P @) IODINE Iodine is extracted either from the mother-liquors of natural sodium nitrates by treatment with sulphur dioxide or sodium hydrogen sulphite, or from marine algae by drymg, incinerating and chemical treatment of the ash. It is a very dense solid (specific gravity 4.95 at 0 OC), with an odour reminiscent of both chlorine and bromine; it is dangerous to inhale. It sublimes at room temperature and turns starch-paste blue. When impure, it occurs in specks or as a coarse powder. When purified by sublimation, it takes the form of brilliant, greyish flakes or crystaIs with a metallic glint; it is then usually put up in glass. It is used in medicine, and also in the manufacture of photographic cherqicals (sodium iodide), dyes (e.g., erythrosines) and medicaments, as a catalyst in organic synthesis, as a reagent, etc. -