Bismuth, reaction with iodine

The reaction is a sensitive one, but is subject to a number of interferences. The solution must be free from large amounts of lead, thallium (I), copper, tin, arsenic, antimony, gold, silver, platinum, and palladium, and from elements in sufficient quantity to colour the solution, e.g. nickel. Metals giving insoluble iodides must be absent, or present in amounts not yielding a precipitate. Substances which liberate iodine from potassium iodide interfere, for example iron(III) the latter should be reduced with sulphurous acid and the excess of gas boiled off, or by a 30 per cent solution of hypophosphorous acid. Chloride ion reduces the intensity of the bismuth colour. Separation of bismuth from copper can be effected by extraction of the bismuth as dithizonate by treatment in ammoniacal potassium cyanide solution with a 0.1 per cent solution of dithizone in chloroform if lead is present, shaking of the chloroform solution of lead and bismuth dithizonates with a buffer solution of pH 3.4 results in the lead alone passing into the aqueous phase. The bismuth complex is soluble in a pentan-l-ol-ethyl acetate mixture, and this fact can be utilised for the determination in the presence of coloured ions, such as nickel, cobalt, chromium, and uranium. 

When treated with iodine pentafluoride, triphenylbismuthane gives triphenylbismuth difluoride but no evidence for the formation of bismuth(V) derivatives was found in the reactions with tris(4-fluorophenyl)bismuthane and tris(trifluoromethyl)bismuthane. Fluorine-aryl (or alkyl) exchange takes place in these cases instead of oxidative fluorination.139140... 

Bismuth(III) iodide has been prepared in the absence of solvents by the reaction of iodine with elemental bismuth1,2 or with bismuth (III) sulfide.3 Alternative methods involve precipitation of bismuth(III) iodide from aqueous solutions of bismuth salts by adding alkali-metal iodides,4 and the addition of bismuth (III) oxide to a solution of iodine and tin(II) chloride in saturated hydrogen chloride.5 In either case the initial product is purified by sublimation, usually in an atmosphere of carbon dioxide. The product obtained by precipitation requires several resublimations for complete purification.6... 

Ignites on contact with antimony, arsenic, boron, iodine, phosphorus, selenium. Ignites when warmed with bismuth, carbon, chromium, lead, sulfur. Incandescent reaction with aluminum, cadmium, cobalt, iron, molybdenum, nickel, potassium, sodium, thorium, titanium, tungsten, uran-... 

The reaction of tetramethyldibismuthine with iodine gives all possible iodo(methyl)bismuthines as well as elemental bismuth [830M1859]. Similarly, tetraphenyldibismuthine reacts with iodine to give iododiphenylbis-muthine as the single product [84JCS(D)2365]. 

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