Oxidizing agents bismuthates

When Bi(OH)3 in strongly alkaline solution is treated with chlorine or other strong oxidizing agents, bismuthates are obtained, but never in a state of high purity. 

Aqueous ceric solutions are widely used as oxidants in quantitative analysis they can be prepared by the oxidation of Ce ( cerous ) solutions with strong oxidizing agents such as peroxodisulfate, S20g ", or bismuthate, BiOg". Complexation and hydrolysis combine to render (Ce" +/Ce +) markedly dependent on anion and acid concentration. In relatively strong perchloric acid the aquo ion is present but in other acids coordination of the anion is likely. Also, if the pH is increased, hydrolysis to... 

Oxidation with ammonium persulfate and dilute caustic soda gives bismuth tetroxide, Bi204. The same product can be obtained by using other oxidizing agents such as potassium ferricyanide and concentrated caustic potash solution. 

A method that can distinguish between the oxidation states Cus+ and Bi5+ in bismuth-based superconductors has been described (33). Bi5+ (BiOs") can oxidize Mn2+ to Mn04", while Cus+ is not a strong enough oxidizing agent to accomplish this task. 

Complex fluorides (LiBiF6, and KBiF6) are known1 and they are weaker oxidizing agents than bismuth(V) fluoride itself. If parallels with potassium tetrafluorocobaltate(III) and co-balt(III) fluoride are valid (see Section 25.1.), then they will also be weaker fluorinating agents. 

Because organobismuth(V) compounds have found considerable use as oxidizing agents, the oxidizing ability of methyl di-l-naphthylbismuthinate [124066-66-6], C21H17Bi02, was investigated. Benzoin yields benzil, naphthalene, and metallic bismuth hydrazobenzene yields azobenzene, and 1,1,2,2-tetraphenylethanediol yields benzophenone. 1,2-Diphenyl-1,2-ethanedione dihydrazone gives diphenylacetylene in 50% yield. Cyclohexane-1,2-diol and 1-phenylethane-l,2-diol, however, were unaffected. 

A redox mechanism for oxidation catalysis was proposed by Mars and van Krevelen (34) for the oxidation of aromatics over V205. This mechanism introduced the concept that lattice oxygen of a reducible metal oxide could serve as a useful oxidizing agent for hydrocarbons. Moreover, it formed the basis for the early work at SOHIO which led to the development of the bismuth molybdate catalyst. Since that time there have been many reports which support the redox concept. 

The only well-established oxide of bismuth is Bi203, a yellow powder soluble in acids to give bismuth salts. It lacks acidic character and is insoluble in alkalis. From solutions of bismuth salts, alkali, or ammonium hydroxide precipitates a hydroxide, Bi(OH)3. Like the oxide, this compound is completely basic. Bismuth(V) oxide is extremely unstable and has never been obtained in pure form. The action of extremely powerful oxidizing agents on Bi203 gives a red-brown powder that rapidly loses oxygen at 100°C. 

Cerium (IV) in solution is obtained by treatment of Ce111 solutions with very powerful oxidizing agents, for example, peroxodisulfate or bismuthate in nitric acid. The aqueous chemistry of CeIV is similar to that of Zr, Hf, and, particularly, tetravalent actinides. Thus Ce gives a phosphate insoluble in 4 M HN03 and an iodate insoluble in 6 M HN03, as well as an insoluble oxalate. The phosphate and iodate precipitations can be used to separate Ce from the trivalent lanthanides. Ce is also much more readily extracted into organic solvents by tributyl phosphate and similar extractants than are the Lnm lanthanide ions. 

Bismuth (Z = 83) is the heaviest stable element in group 15 (VA) of the periodic table (see Periodic Table Trends in the Properties of the Elements). The Bi isotope, which is 100% abundant, has a 9/2 nuclear spin. Bi, an alpha emitter is used in nuclear medicine as a radiotherapeutic agent. Bismuth has two stable oxidation states Bi(V), corresponding to complete loss of the valence electrons, and Bi(III), a lower oxidation state that retains two valence electrons. Both oxidation states are diamagnetic. The latter is more stable and more common since Bi(V) has a large reduction potential ... 

The berkelium (IV) extraction coefficients have been determined by stripping solvents previously loaded with tetravalent cerium and berkelium in the presence of sodium bismuthate. Sodium bismuthate has been found to be an efficient oxidizing agent for trivalent cerium. Because of its small solubility it does not affect the distribution coefficients of tetravalent cerium. These two properties have been demonstrated by comparing the distribution coefficients of cerium (IV) measured by spectrophotometry with those of cerium oxidized by sodium bismuthate and measured by beta counting of the cerium isotope tracer. The data are summarized in Table I and indicate no real difference in the distribution coefficients of cerium obtained by these two methods when using trilaurylmethylammonium salts-carbon tetrachloride as solvent. 

Inorganic bismuth compounds usually have a -I- 3 or -t- 5 oxidation state. The -I- 5 oxidation state is a strong oxidation agent, e.g. NaBiOj or BiFj. In gases, such as BiCl or BiO, in BijAlClJ and in alloy-like compounds, such as BiS or BiSe, bismuth can rarely have a + 1 or -h 2 oxidation state, and + 1, 0 and — 1 are present in polynuclear ionic... 

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