Metals, separation Mixture

The shift of the half-wave potentials of metal ions by complexation is of value in polarographic analysis to eliminate the interfering effect of one metal upon another, and to promote sufficient separation of the waves of metals in mixtures to make possible their simultaneous determination. Thus, in the analysis of copper-base alloys for nickel, lead, etc., the reduction wave of copper(II) ions in most supporting electrolytes precedes that of the other metals and swamps those of the other metals present by using a cyanide supporting electrolyte, the copper is converted into the difficultly reducible cyanocuprate(I) ion and, in such a medium, nickel, lead, etc., can be determined. 

The rapid and reversible formation of complexes between some metal ions and organic compounds that can function as electron donors can be used to adjust retention and selectivity in gas and liquid chromatography. Such coordinative interactions are very sensitive to subtle differences in the composition or stereochemistry of the donor ligand, owing to the sensitivity of the chemical bond towards electronic, steric and strain effects. A number of difficult to separate mixtures of stereoisomers and isotopomers have been separated by complexation chromatography. 

Reduction of the metal dimer [CpMo(NO)l2]2 with Na/Hg in the presence of a variety of acyclic dienes generates the (diene)MoCp(NO) complexes in moderate to low isolated yield (equation 8)12,31,89. For the majority of diene ligands, complexes 60 are formed exclusively as the s-trans isomers as evidenced by NMR spectroscopy and single-crystal X-ray diffraction analysis. In comparison, complexation of the 2,3-dimethyl-l,3-butadiene initially gives a separable mixture of the s-trans (60) and s-d.v-complex (61). The s-cis isomer isomerizes to the more thermodynamically stable s-trans isomer in solution (THF, 1/2 = 5 min C6H6, ti/2 = 24 h). 

The Biotherm Process does not destroy wastes it rather separates mixtures into streams that can be used more safely, disposed of, or treated. The process does not treat metals. Solids with high percentages of insoluble metals may require special management or additional treatment prior to disposal. 

This method has the advantage of generating the desired anions quantitatively and avoids the formidable task of separating mixtures of polynuclear anions into their analytically pure components. The trinuclear anions may be isolated as alkali metal salts and used in situ or may be quantitatively metathesized to form alkyl ammonium, arsonium, or phosphonium salts. Therefore, we have found these alkali metal dianions to be a very useful, general starting material for a variety of reactions. 

Separation of diastereoisomeric peptides by HPLC is more common. Since each diastereo-isomer has different physicochemical and biological properties, this is of great interest. Separations of diastereoiosomeric di- and tripeptides have usually been performed on reversed-phase columns. Cahill et al. (119) separated diastereoisomeric amino acids and derivatized dipeptides using esters of the /V-hydroxysuccinamide of f-butyl carbonyl-L-amino acid on Cl8 and C8 columns. Linder et al. (120) separated amino acid and peptide derivatives on an RP-C8 column, adding a metal chelate. Mixtures of DL and LD-dipeptides can be separated by RP-HPLC into two peaks, one containing LL- and DD-isomers, the other containing LD and DL-isomers. Sep-... 

Figure 13.4 Schematic of a diffusion dialysis process to separate acids from heavy metal/acid mixtures...

HPLC units have been interfaced with a wide range of detection techniques (e.g. spectrophotometry, fluorimetry, refractive index measurement, voltammetry and conductance) but most of them only provide elution rate information. As with other forms of chromatography, for component identification, the retention parameters have to be compared with the behaviour of known chemical species. For organo-metallic species element-specific detectors (such as spectrometers which measure atomic absorption, atomic emission and atomic fluorescence) have proved quite useful. The state-of-the-art HPLC detection system is an inductively coupled plasma/MS unit. HPLC applications (in speciation studies) include determination of metal alkyls and aryls in oils, separation of soluble species of higher molecular weight, and separation of As111, Asv, mono-, di- and trimethyl arsonic acids. There are also procedures for separating mixtures of oxyanions of N, S or P. 

Azido-3,6-drniethylpyrazine (238) gave 2,5-dimethyl-l-imidazolecarbonitrile (239) with loss of N2 (neat, 230°C, in preheated metal bath, 1 min 89%) 1314 the same substrate (238) gave a separable mixture of product (239) and 2,... 

Trace quantities of metal are found in the igneous rocks the composition of these metals differs considerably from the meteoritic abundance pattern and is therefore easily distinguished. Of course, the metal from the lunar igneous rocks will also become admixed to soils. Hence, the metal separates of the soil samples are a mixture of meteoritic and indigenous metal from lunar rocks. As can be seen from Table 10, the latter contributes significantly only to metal from soil 15601. Measurements have been carried out on individual metal grains down to particles of less than 10-6 g weight via electron microprobe for Fe, Ni, and Co and via neutron activation for Fe, Co, Ni, Cu, Ga, As, W, Ir, and Au 6)... 

Metallurgy. The extraction of metals from their compounds dissolved in molten salts, the separation of metals from mixtures in solution, and the... 

Description of the process. The simplified process flow diagram is shown in Figure 16.12. The shredder waste (ASR, plastic and electronic waste as well as MSW) is fed in an IRFB, which operates in a reducing atmosphere and at temperatures as low as 500-600°C, allowing easy control of the process. The IRFB reactor separates the combustible portion and the dust from the inert and metallic particles of the fed waste the obtained mixture of metallic and inert particles is sent to a mechanical metal separation while fuel gas and carbonaceous particles are burnt in a cyclonic combustion chamber for energy production and fine ash vitrification. Metals such as aluminium, copper and iron can be recycled as valuable products from the bottom off-stream of the IRFB as they are neither oxidized nor sintered with... 

In an inert-atmosphere dry-box, 2.36 g (0.01 mole) of niobium tetrachloride is suspended in 25 ml of acetonitrile in a 100-ml round-bottomed flask equipped with a magnetic stirring bar. Niobium(IV) chloride is conveniently prepared by reduction of niobium(V) chloride with aluminum metal. " This mixture is stirred for ca. 1 hr and then 5.84 g (0.06 mole) of potassium thiocyanate dissolved in 25 ml of acetonitrile is added. Stirring is continued for 4 hr to allow for complete reaction. The red solution is filtered through a medium-porosity sintered-glass frit, separating the insoluble potassium chloride from the soluble K2[Nb(NCS)e]. The KCl precipitate is washed with three 5-ml portions pf... 

Clathrochelate ribbed-functionalized tris-dioximates have attracted interest because they offer scope for the synthesis of polynuclear complexes with targeted structural parameters and physicochemical properties (see above). In most instances, it is not necessary to functionalize all a-dioximate fragments, and it appears to be sufficient to modify only one of the three ribs in the clathrochelate framework to alter the properties significantly. Several feasible synthetic routes to clathrochelate monoribbed-functionalized tris-dioximates have been proposed in Ref. 68. A direct template condensation of the mixture of a-dioximes with Lewis acids on a metal ion (Scheme 15, Route I) leads to the formation of a poorly separable mixture of nonsymmetric and symmetric products, in which the latter predominate. Halogenation of the initial clathrochelate... 

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