Bismuth complexing agents

Direct Titrations. The most convenient and simplest manner is the measured addition of a standard chelon solution to the sample solution (brought to the proper conditions of pH, buffer, etc.) until the metal ion is stoichiometrically chelated. Auxiliary complexing agents such as citrate, tartrate, or triethanolamine are added, if necessary, to prevent the precipitation of metal hydroxides or basic salts at the optimum pH for titration. Eor example, tartrate is added in the direct titration of lead. If a pH range of 9 to 10 is suitable, a buffer of ammonia and ammonium chloride is often added in relatively concentrated form, both to adjust the pH and to supply ammonia as an auxiliary complexing agent for those metal ions which form ammine complexes. A few metals, notably iron(III), bismuth, and thorium, are titrated in acid solution. 

We could not find any study of Bi(III) ions in aqueous solutions except that Wang et al. [132] obtained nanorods of bismuth sulphide by sonicating an aqueous solution of bismuth nitrate and sodium thiosulphate in the presence of complexing agents such as ethylenediamine tetraacetic acid, triethanolamine and sodium tarta-rate. Similar results were found when thioacetamide was used in place of sodium thiosulphate as a source of sulfur. However, the results improved with higher yield... 

The main interfering metals in the copper determination are Fe, Bi, Mn, Ni, Co, Cr, Mo and U, which form coloured complexes. The selectivity of the method is considerably enhanced by the use of EDTA as a masking agent. In a tartrate or citrate medium at pH 8-9, Fe, Mn, Ni and Co are masked by EDTA, as are Cd, Pb, Zn, and In, which form colourless complexes with DDTC. Of the metals forming coloured compounds with DDTC, only Bi, Tl(III), and Cu are not masked. Thallium, when reduced to T1(I), does not interfere. Bismuth can be stripped from the organic extract, containing copper and bismuth diethyidithiocarbamates, with 5 M HCl. Copper diethyidithiocarbamate is decomposed by cyanide, whereas the bismuth complex remains unaffected. 

Bismuth sulfide (31283) films have been deposited by using either TU, TA or thiosulfate processes with various complexing agents (TEA, NTA, EDTA) [16, 20-... 

Interferences caused by transition metal ions have been eliminated or reduced by adding various reagents, such as complexing agents, to the sample solution. The addition of these reagents prevents the reduction or precipitation of the interfering metal ion. The interference caused by cadmium, iron, copper, cobalt, and silver on the determination of arsenic can be eliminated with potassium iodide. An addition of potassium iodide reduces the interference of nickel in the determination of arsenic, that of iron in the determination of antimony, and the influence of copper in the determination of bismuth. 

EDTA (ethylenediaminetetraacetic acid) forms stable metal chelates with a number of metal ions. Using this reagent as a complexing- agent, arsenic, bismuth, and selenium can be determined without any interference in the presence of nickel and cobalt. The cobalt-EDTA chelate is stable in 5 M HCl solution, whereas the corresponding bismuth complex is not. The influence of copper on the determination of arsenic can also be eliminated with EDTA, but not in the determination of selenium. Thiourea has been used to eliminate the influence of copper in the determination of antimony and sodium oxalate to eliminate the influence of copper and nickel in the determination of tin. An addition of thiosemicarbazide and 1,10-phenanthro-line reduces the interference of copper, nickel, platinum, and palladium in the determination of arsenic. 

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... 

The solution should be free from the following, which either interfere or lead to an unsatisfactory deposit silver, mercury, bismuth, selenium, tellurium, arsenic, antimony, tin, molybdenum, gold and the platinum metals, thiocyanate, chloride, oxidising agents such as oxides of nitrogen, or excessive amounts of iron(III), nitrate or nitric acid. Chloride ion is avoided because Cu( I) is stabilised as a chloro-complex and remains in solution to be re-oxidised at the anode unless hydrazinium chloride is added as depolariser. 

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. 

Organobismuth(in) complexes may mediate a number of reactions involving aUyhc compounds and aldehydes. In these reactions, an aUyl halide is treated with a bismuth(lll) salt such as Bids and a reducing agent (Zn, Fe, or Al) in the presence of an aldehyde (equation 13). A likely reaction... 

Newer agents under investigation include tris(tropolonato) Bi(III) and nitratobis(tropolonato)Bi(in) a host of bis (mercaptoethanol)Bi(III) complexes, which are formed with 0,S-bidentate chelation, with and without deprotonation of the hydroxyl oxygen and usually having an axial fifth ligand and sialic acid derivatives of Bi(III). The interactions of Bi(III) and its compounds with metallothionein, serum albumin and transferrin have been studied by a variety of groups, as have a number of enzymes that may be related to the mechanism(s) of action of bismuth in treating ulcers. 

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