Thermodynamic stability of neodymium nitrate complex with 1,10-phenanthroline

The thermodynamic stability of neodymium nitrate complex with 1,10-phenanthroline (Phen) was determined by mass spectrometry. The complex was formulated as Nd(NO₃)₃ · 2C₁₂H₈N₂ on the basis of elemental analysis. Mass spectrometry allowed us to characterize the decomposition of Nd(NO₃)₃ · 2C₁₂H₈N₂ thermodynamically. The formation enthalpy of this complex is ?1058.0 kJ/mol.     

Extraction and spectrophotometric determination of nickel based on the formation of a ternary complex with cadion and 1,10-phenanthroline

Summary A sensitive and selective spectrophotometric method has been developed for the determination of nickel, based on the formation of red ternary complex of nickel with cadion and 1,10-phenanthro- line in alkaline solution (0.5N NaOH). The complex is quantitatively extracted by chloroform and exhibits an absorption maximum at 505 nm. Beer's law is obeyed in the concentration range of 0–2.5g of Ni(II)/5 ml chloroform. The Sandell sensitivity and molar absorptivity of the reaction are 0.000587g cm^–2 and 1.0×l0⁵l· mol^–1·cm^–1, respectively. The method has been applied to the determination of nickel in alloy steels, aluminium alloys and soils.

---

Extraktion und spektrophotometrische Bestimmung von Nickel mit Cadion und 1,10-Pbenanthrolin als ternärer Komplex

Zusammenfassung Eine empfindliche und selektive Methode zur Bestimmung von Nickel mit Cadion und 1,10-Phenanthrolin wurde ausgearbeitet. Sie beruht auf der Bildung eines roten ternären Komplexes in alkalischer Lösung (0.5N NaOH). Bei 505 nm entspricht die Färbung dem Beerschen Gesetz zwischen 0 und 2,5g Ni(II)/5 ml Chloroform. Der Komplex läßt sich mit Chloroform extrahieren. Die Empfindlichkeit der Reaktion beträgt 0,000587g· cm^–2 und die molare Absorption 1.0×10⁵l·mol^–1·cm^–1. Die Bestimmung von Nickel in Stahl, Aluminiumlegierungen und Böden ergab zufriedenstellende Resultate.

     

Conductometric titration of metal acetates in aqueous medium

Fifteen metal acetates in aqueous medium have been conductometrically titrated with trichloro-acetic acid. The method has been applied to the titration of mono- and bivalent metals and angles at the equivalence point are sharp enough to allow accurate results to be obtained. Metal salts of acids weaker than acetic can be determined following solution in an excess of acetic acid and titration, because the weaker acid which is displaced does not interfere.     

Conductometric titration of thiosulfate using new-type conductivity cells

The conductometric titration of thiosulfate with silver ions using non-conventional conductivity cells is described. For this purpose conductivity cells with different cell constants and electrode constructions, equipped with silver, amalgamated silver, stainless-steel and polished platinum electrodes were used. Two well-resolved break-points were observed at 1:1 and 2:1 silver/thiosulfate stoichiometries. Accurate conductometric determinations can be made, using the second break-points of the titration curves as equivalence points, in the range of thiosulfate concentrations 10(-4)-10(-2) M. Reverse titrations are less accurate.     

High frequency titration methods in the investigation of complex formation

High frequency titration is a valuable tool in the study of complex formation in solutions, and the breaks in the titration curves can be used, in conjunction with the results of other physical methods, to determine the composition of the complexes formed. High frequency titration and other methods have been used to study the complexes formed by thorium, indium, plutonium(V) and boron with various complexing agents, and to develop methods for the determination of thorium and yttrium in rare earth mixtures, and of indium in the presence of zinc, cadmium, aluminium, nickel and cobalt.     

The spectrophotometric determination of thallium(iii)by ternary complex formation

If thallium(III) is added to an aqueous solution of potassium thiocyanate containing a large amount of pyridine in the pH range 5.2–5.5, a yellow solution which is stable in diffuse light is obtained. The yellow colour can be measured at 405 nm for the colorimetric determination of thallium(III) in the range 20–300 μg Tl ml^-1. The complex is a mixed ligand complex with a metal-ligand ratio of 1:2:2. Thallium(I) does not interfere. The interference of various other metal ions and anions is discussed.     

Spectrophotometric determination of maneb by ternary complex formation with PAR and CTAB

A rapid, simple, direct, and sensitive method has been developed for the determination of maneb (manganese ethylenebisdithiocarbamate) based on the formation of manganese-4-(2′-pyridylazo) resorcinol complex by a ligand displacement reaction, which is rendered water soluble by a cationic surfactant cetyltrimethylammonium bromide (CTAB) by the formation of an ion association complex. Beer's law is obeyed over the concentration range 0.08–2.4 μg/ml of the final solution at 500 nm in pH range 8–12. The molar absorptivity and Sandell's sensitivity are calculated to be 8.84 × 10⁴ l.mol⁻¹.cm⁻¹ and 0.003 μg/cm², respectively. The developed method has been applied to the determination of maneb in commercial formulations, synthetic mixture, grain samples and vegetables.     

铒(Er)-L-组氨酸-邻菲啰啉三元配合物的合成与性质

在乙醇介质中,合成了铒(Er)-组氨酸(L-His)-邻菲啰啉(Phen.H2O)三元稀土配合物,利用摩尔电导率、络合滴定分析、元素分析、红外光谱(IR)和热重-差热(TG-DTA)等分析测试,推测配合物的化学组成为:[Er(L-His)3Phen]Cl3.3H2O。初步研究了配合物的电化学性质和生物活性;其中稀土配合物对革兰氏阴性菌大肠杆菌、革兰氏阳性枯草芽孢杆菌都有较好的抑制作用,特别是对革兰氏阴性菌大肠杆菌抑制效果更好。并通过循环伏安测定了配合物在铂盘工作电极上的电化学行为,在HAc-NaAc缓冲溶液(pH≈6.0)中ErCl3.6H2O和配合物{[Er(L-His)3Phen]Cl3.3H2O}在-0.3 V～-1.0 V(vs.SCE)电位范围内均表现出电化学活性,配合物的电化学活化中心是Er3+,该配合物为准可逆体系,且配合物的还原峰电流与浓度和扫描速率呈现递增关系。     

Chelate complex formation as a basis for titration processes

Metal cations can be looked upon as LEWIS acids and their reaction with ligands during complex formation can be compared to the addition of the proton to a base. The complex formation reactions, however, lack sharp and definite endpoints and metal cations therefore cannot be titrated with ammonia, cyanide and other ligands in the same way as the hydrogen ion can be titrated alkalimetrically. The theoretical reason for this fact is discussed and it is shown that complex formations gain the characteristic properties of neutralisation reactions if the simple ligands are replaced by a polydentate group which is able to satisfy not only one, but several of the coordination points of the metal cation. A great number of titration processes can be based on such reactions.     

恒电位氟-铝配位滴定法测定铝的研究

以氟离子溶液作滴定剂,氟离子选择性电极作指示电极,对恒电位配位滴定法测定铝进行了研究,导出了该测定法的计算模型。测定结果的准确度受电位的控制误差对滴定剂体积误差的影响及滴定剂体积的相对误差两个因素影响。在滴定的中间位置,准确度比较高。随着滴定剂体积的增加,测定的灵敏度增加。方法可用于金属铝及锌一铝合金中铝的测定。     

Dynamics of ternary complex formation in the reaction of diaquoanthranilato-N,N-diacetatonickelate(II) with 2,2′-bipyridine and 1,10-phenanthroline

Dynamics of ternary complex formation in the reaction of diaquoanthranilato-N, N-diacetatonickelate(II) with 2,2′-bipyridine and 1,10-phenanthroline. $\rm Ni(ada)(H_2O)_2^{-}$ $+$ $L\rightleftharpoons Ni(ada)(L)^{-}$ $+$ $2 H_20;$ $- {{d[Ni(ada)^{-}]}\over{dt}}$ $=$ $k_f[Ni(ada)^{-}][L]+k_d\ [Ni(ada)(L)];$ $\ ada^{3-}=$anthranilate-N, N-diacetate; and L=bipy or phen. The kinetics of formation of ternary complexes by diaquoanthranilato-N, N-diacetatonickelate(II). [Ni(ada)(H₂O)]⁻ with 2,2′-bipyridine (bipy) and 1,10-phenanthroline (phen) have been studied under pseudo-first-order conditions containing excess bipy or phen by stopped-flow spectrophotometry in the pH range 7.1–7.8 at 25°C and λ = 0.1 mol dm⁻³. In each case, the reaction is first-order with respect to both Ni(ada)⁻ and the entering ligand (ie., bipy, phen). The reactions are reversible. The forward rate constants are: $k^{\rm Ni(ada)}_{\rm Ni(ada)(bipy)}=0.87\times10^3{\rm dm}^3 {\rm mol}^{-1}{\rm s}^{-1}$, . $k^{\rm Ni(ada)}_{\rm Ni(ada)(phen)}=1.87\times10^3{\rm dm}^3 {\rm mol}^{-1}{\rm s}^{-1}$; and the reverse rate constants are: $k^{\rm Ni(ada)(bipy)}_{\rm Ni(ada)}=1.0{\rm s}^{-1}$ and $k^{\rm Ni(ada)(phen)}_{\rm Ni(ada)}=2.0{\rm s}^{-1}$. The corresponding stability constants of ternary complex formation are: and , . The observed rate constants and huge drops in stability constants in ternary complex formation agree well with the mechanism in which dissociation of an acetate arm of the coordinated ada³⁻ prior to chelation by the aromatic ligand occurs. The observations have been compared with the kinetics of ternary complex formation in the reaction Ni(ada)⁻ - glycine in which the kinetics involves a singly bonded intermediate, N(ada)((SINGLE BOND)O(SINGLE BOND)N)²⁻ in rapid equilibrium with the reactants followed by a sluggish ring closure step. The reaction with the aromatic ligands conforms to a steady-state mechanism, while for glycine it gets shifted to an equilibrium mechanism. The cause of this difference in mechanistic pathways has been explained. © 1996 John Wiley & Sons, Inc.     

Stabilization of germanium(ii) by complex formation in iodimetric titration of germanium

Four factors are important in the reduction of germaniuin(IV) by hypophosphite, namely, proper acidity, temperature, proper concentration of complexing ligand, and time of heating. The complexing ligand is needed to stabilize the germaium(II) ions. Halides, with the exception of fluoride, and phosphate are good complexing ligands for germanium. Tin is quantitatively reduced and titrated under the same conditions. Many foreign ions do not interfere, so that prior separation of germanium can often be avoided. Successful results are presented for titrating germanium in the presence of many metals and for direct determination of germanium in actual samples. Germanium after reduction may be titrated with an iodate solution potentiometrically. The formal oxidation potentials of some germanium half-reactions were estimated and used to interpret the stabilization of germanium(II) by complex formation. Phosphoric acid is recommended as the reduction medium.     

Fluorimetric determination of sulphate by ternary complex formation with zirconium and biacetylmonoxime nicotinylhydrazone

A fluorimetric procedure for the determination of sulphate (0.5-6 mug ml ) based on the formation of a ternary complex with biacetylmonoxime nicotinylhydrazone and zirconium(IV) is described. The excitation and fluorescence maxima are at 415 and 505 nm, respectively. The method is rapid and the procedure reproducible. The precision is +/- 2% near to the middle range of the calibration curves. There is no interference from most common ions. Phosphate and fluoride are tolerated at 100-fold molar ratio to sulphate. The method has been applied to the determination of sulphate in a variety of water samples.     

Determination of fluoride with thorium nitrate by catalytic titration

Amperometry, constant-current potentiometry and spectrophotometry were used to follow the course of catalytic titrations of fluoride and silicofluoride with thorium nitrate. The hydrogen peroxide-iodide system was used as the indicator reaction. Titrations were performed in 50% ethanolic acetate buffer, pH 3.6. Amounts of 3.70-6.85 mg of ammonium fluoride, 5.53-10.79 mg of potassium fluoride and 4.34-8.41 mg of sodium silicofluoride were determined with a maximum average deviation of 0.9%. The results obtained are in good agreement with those of comparable methods.     

Fluorimetric determination of magnesium by ternary complex formation with pyridoxal nicotinylhydrazone and amines

The synthesis, characteristics and analytical applications of pyridoxal nicotinylhydrazone are described. This compound reacts with magnesium(II) in the presence of ammonia, ethylenediamine or pyridine, to produce a 1:1:1 Mg(II)—pyridoxal nicotinylhydrazone—amine fluorescent complex (λ_ex 395 nm, λ_em 480 nm). A fluorimetric method is proposed for the determination of magnesium(II) (20–100 ng ml^-1 in the solution measured); isobutanol is used to extract the complex, reducing the number of interferences.     

Luminescence and magnetic properties of europium(III) nitrate complex with 1,10-phenanthroline

Luminescent and magnetic properties of the europium nitrate complex with 1,10-phenanthroline synthesized in the traditional way by precipitation from water-ethanol medium and by the method of mechanical activation were investigated. Correlations between luminescent and magnetic properties of the complex compounds were revealed. The higher value of molar magnetic susceptibility ??_m was shown to be typical for the highly dispersed europium compound obtained by mechanochemistry method due to the presence of the paramagnetic ion Eu²⁺.     

Thermodynamics of complex formation in ternary liquid mixtures containing acetonitrile

Vapor—liquid and liquid—liquid equilibria and excess enthalpies for ternary mixtures formed from acetonitrile, benzene, n-heptane, toluene, and carbon tetrachloride are successfully correlated with a modified version of the associated solution theory proposed by Lorimer and Jones in 1977, which assumes two types of self-association for acetonitrile and binary complexes between acetonitrile and unsaturated hydrocarbons and does not include any ternary parameters.