Solvent extraction of metals with commercial oxime extractant (LIX 622)

The extraction characteristics of some selected metals from an aqueous buffered solution by LIX 622, a commercial oxime extractant have been studied. The pH_1/2 values for extracting different metals with 5 v/v% LIX 622 extractant in methyl isobutyl ketone (MIBK) have been obtained. The order of extraction of metals with LIX 622 extractant as a function of pH_1/2 value is determined and results agree well with the order obtained using salicylaldoxime as chelating ligand for the extraction of these metals.     

Selective potentiometric determination of phenol and alkylphenols in nonaqueous extracts

Some systems of extraction of phenols from aqueous solutions (R=97–99%) are recommended. Methods of separate extraction-potentiometric determination of phenol and alkylphenols in nonaqueous extracts are developed.     

Spectrophotometric determination of iron (II) with quinisatin oxime

A sensitive spectrophotometric determination of iron is based on the blue color (absorption maximum at 660 mμ) formed by reaction of iron (II) with quinisatin oxime in buffered solution containing ethyl alcohol and a small amount of dimethylformamide. The color develops rapidly and is stable for a few h. The absorbance is well reproducible, and conforms to Beer's law. The optimum concentration range at 1 cm optical path is about 0.5 to 2.5 p.p.m. of iron. Small amounts of iron(III) are reduced by the reagent and cause no difficulty. Cobalt and nickel interfere. Iron(II) and quinisatin oxime react in a 1:3 mole ratio; some possible modes of complex formation are suggested.     

The nonaqueous,potentiometric titration of free hydrochloric acid in chloride-containing polymers

The thermal and/or catalytic degradation of chloride-containing polymers causes dehydrohalogenation which produces hydrochloric acid. A nonaqueous method has been developed for the termination of hydrochloric acid. The sample is dissolved in tetrahydrofuran and titrated potentiometrically with a standard tetrabutylammonium hydroxide solution in a 7.5% (V/V) aqueous tetrahydrofuran solution with a combination glass-calomel electrode. The method has a relative precision of ±3.7% at the 95% confidence limit and a sensitivity of 25 ppm HCI.     

Photoreductive decarboxylation of carboxylic acids via their benzophenone oxime esters

Decarboxylation of various carboxylic acids, including ∝β- andamino acids, is performed by the photolysis of their benzophenoneoxime esters in isopropanol in the presence of t-butyl mercaptane,and corresponding decarboxylated products are obtained in goodyields under mild photolytic conditions.     

The spectrophotometric determination of cobalt after extraction of tetramethylene-bis(triphenyl-phosphonium) tetrathiocyanatocobaltate(II) with microcrystalline benzophenone

Cobalt (0–130 μg) is determined spectrophotometrically at 625 nm after its adsorptive extraction as tetramethylene-bis(triphenylphosphonium) tetrathiocyanatocobalt(II) on microcrystalline benzophenone at pH 6.5 after dissolution of the solid phase in acetylacetone. The system is applied to the determination of cobalt (0.2–10%) in high-speed tool steels without prior separation of iron.     

Synthesis and characterization of copper and nickel complexes of LIX63 oxime

Several complexes of 5,8-diethyl-7-hydroxy-6-dodecanone oxime [H₂L] with Cu(II) and Ni(II) have been synthesized and characterized by means of a number of techniques including elemental analysis, IR spectra, magnetic susceptibility measurements, electronic absorption spectra, NMR spectra, and mass spectra. The results indicate that Cu(II) and Ni(II) generally form analogous, isomorphous complexes, although no bis-[H₂L] complex with Cu(II) has been isolated. [Cu(L)]_n and [Ni(L)]_n are oligomeric complexes with pseudo-octahedral geometry. [Ni(HL)₂] is cis-square-planar (C_2ν) with bifurcated hydrogen bridges. [Ni(H₂L)₃SO₄] and [Cu(H₂L)₃SO₄] have octahedral symmetry in which the sulphate is coordinated as a unidentate ligand and the oxime is functioning as a neutral ligand.     

2-羟基-4-(1-甲基庚氧基)二苯甲酮肟萃取钯(II)的动力学和机理

本文报道2-羟基-4-(1-甲基庚氧基)二苯甲酮肟(N530)在盐酸介质中萃取钯(II)的平衡和动力学研究结果.用分配法测定了N530的基本常数.平衡研究表明,N530萃取钯反应的表现平衡常数K~ex为10~[16.88±0.04]氯仿作稀释剂)和10~[18.00±0.01](正十二烷作稀释剂).动力学研究表明,水相中的取代反应为决速步骤,K,1为2.42x10~2L.mol^-1.s^-1.测得萃取反应活化能为30.0±3.2(氯仿)和28.9±1.9KJ.mol^-1(正十二烷),与稀释剂无明显关系.界面特性研究表明,界面饱和时有机相体相浓度为10^-2mol.L^-1,小于测定速率方程时的浓度,这些都进一步证实了水相反应机理而排斥了界面反应机理.     

Two-phase potentiometric metal extraction titrations of silver(I), copper(II) and cadmium(II) using some cation-exchangers as extractants

The use of two-phase potentiometric metal extraction titrations to study solvent extraction equilibria is described. The method provides a highly reproducible and convenient manner by which to determine extraction behaviour. The system was tested on a number of acidic extractants, namely D2EHPA, Ionquest 801, Cyanex 272, naphthenic acid and Versatic 10 acid. The extraction from an aqueous nitrate medium of silver(I), copper(II) and cadmium(II) was studied. The potentiometric data were used to obtain extraction curves and elucidate the nature of the extracted complexes by slope analysis and non-linear least squares treatment. In general, the following extraction order was obtained: D2EHPA > Ionquest 801 > Cyanex 272 and naphthenic > Versatic 10 for copper(II) and cadmium(II). Organophosphorus acids were shown to form complexes of the nature of Cu(HA(2))(2) with copper(II) and carboxylic acids formed dimeric complexes (CuA(2)(HA))(2). With cadmium octahedral complexes of the form CdA(2)(HA)(4) occurred. The extraction of silver(I) by Versatic 10 gave a dimeric complex (AgA(HA))(2). HA denotes the extractant in the acid form.     

Selective potentiometric determination of Bi(III) with a coated-wire electrode

A bismuth-selective electrode based on the chlorobismuthate(III) salt of Aliquat 336 is described. The electrode gives nearly linear response in the bismuth concentration range 10⁻¹–10⁻⁴M. The optimum solution conditions for operation of the electrode have been determined together with possible interference effects. The application of the electrode to analysis of samples containing large amounts of other metals is illustrated by the determination of bismuth in pharmaceuticals. The electrode is shown to give results by direct potentiometry and the standard-addition method which differ from atomic-absorption results by not more than 2%.     

Solid-state ion-selective electrodes for the potentiometric determination of hexacyanoferrate (II)

Hexacyanoferrate(II)-sensing electrodes were prepared by mixing Ag₂S and Ag₄Fe (CN)₆. The 6:1 Ag₂S/Ag₄Fe (CN)₆ provided the best potentiometric response and speed of response. The log concentration vs. potential curves were linear with Nernstian slope (14.8 mV/decade) over the range 10^?1-10^?6 M hexacyanoferrate (II) at pH 7.00 with constant ionic strength. Interferences included iodide, sulfide and bromide. This electrode was used as indicator in potentiometric titrations of hexacyanoferrate (II).     

The nonaqueous microtitration of pentaerythritol tetranitrate (PETN)

Summary PETN has been determined by nonaqueous titration as an acid in pyridine and l, l,3,3-tetramethylguanidine. The titrant was tetrabutylammonium hydroxide. Endpoints were determined potentiometrically by a glass/modified calomel electrode system, or by two polarized platinum electrodes. The method may be applicable to other very weakly acidic compounds for which no other titrimetric methods are currently available.

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Zusammenfassung Pentaeerythrit-Tetranitrat wurde als Säure gelöst in Pyridin und 1,1,3,3-Tetramethylguanidin mit Tetrabutylammoniumhydroxid titriert. Der Endpunkt wurde potentiometrisch mit dem System Glaselektrode/modifizierte Kalomelelektrode oder mit zwei polarisierten Platinelektroden bestimmt. Das Verfahren dürfte sich auch für andere sehr schwache Säuren eignen, für die andere maßanalytische Methoden zur Zeit nicht verfügbar sind.

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Work performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore Laboratory under contract number W-7405-ENG-48.     

The determination of molybdenum in high-nickel alloys by potentiometric titration with cerium(IV) solutions

A combination of ion-exchange separation and potentiometric titration is used in the determination of the molybdenum content of various high-nickel alloys that contain more than 4% molybdenum. The molybdenum(VI) fraction of a sample separated by ion exchange is reduced with tin(II) chloride and titrated with cerium(IV) sulfate. The method facilitates accurate, routine determinations without the extreme care that is required by the standard photometric method or the length and complexity of the gravimetric method. By suitable adjustment of the sample size or the strength of the titration solution, effective titrations can be conducted on samples containing up to 100% molybdenum.     

Sequential injection with lab-at-valve (LAV) approach for potentiometric determination of chloride

Sequential injection with “Lab-at-Valve (LAV)” approach is demonstrated for potentiometric determination of chloride. The LAV flow-through electrode system consists of two Ag/AgCl electrodes: one as a reference electrode, silver chloride activated surface-silver wire soaked in a constant-concentration chloride ion solution in a small tube covered with a polymer-membrane, another as a working electrode (a similar silver chloride activated surface-silver wire) placed in a flow channel. The electrode system is attached at one port of a 10 port multiposition valve. A modified autoburette was used as a propelling device. Using SI operation via a program written in-house, based on LabVIEW^®, a standard/sample is inserted, via the selection valve, in potassium nitrate as an electrolyte and water is used as a carrier. The zones are transported from the holding coil to the flow cell to monitor the difference in potential due to concentration cell behavior. The potential difference is then recorded as a peak. Peak height is proportional to logarithm of chloride concentration. The SI-LAV for chloride determination is very simple, fast, precise, accurate, automatic and economical. Applications to mineral drinking water and surface water have been made. The results agree with those of IC and titrimetric methods.     

Effect of surfactants on the kinetics of nickel(II) extraction by 2-hydroxy-5-nonylacetophenone oxime (LIX 84) in an n-heptane/water system

The initial reaction rates of the extraction of nickel(II) by 2-hydroxy-5-nonylacetophenone oxime (HNAPO) in a two-phase oil/water system was measured using a total internal reflectance static transfer cell. A two-step reaction mechanism between nickel(II) and HNAPO was found to satisfactorily explain the observed initial reaction rate (R(int)). The addition of neutral surfactants, nonionic octaethylene glycol mono-n-dodecyl ether and zwitterionic n-dodecyldimethyl-3-ammonio-1-propanesulfonate, decreased R(int), which could be accounted for with a competitive surface adsorption model. The presence of the anionic surfactant sodium dodecyl sulfate accelerated and then decelerated R(int), while the cationic surfactant dodecyltrimethylammonium chloride caused a decrease. The effects of these charged surfactants were accounted for using a combination of a competitive surface adsorption model and the Boltzmann distribution of charged species.