Copper In Aqueous Solution Research Articles

Spectra of Cu(II)‐Complexes in Aqueous Solutions at High Temperatures and Pressures

AbstractThe influence of pressure, temperature and chloride‐concentration on the optical spectra of copper(II)ions in aqueous solution has been investigated.The measurements could be extended to 400 °C at a pressure of 2000 bars. In dilute aqueous solutions of copper(II)chloride the hexaquocopper‐ (II)complex is prevailing. With increasing temperature and concentration of chloride the copper(II)tetrachlorocomplex is formed via some intermediate compounds. The composition of some of the intermediate compounds was deduced from the spectra obtained.

Film dissolution during sulphide tarnishingof copper in aqueous solutions of thiourea and alkaline polysulphide

The tarnishing of copper in aqueous solutions of thiourea and alkaline potassium polysulphide has been examined by coulometric reduction, weight-change techniques and scanning electron microscopy. Potentiodynarnic reduction indicated the presence of up to six constituents but most tarnish films contained only two main sulphide components and one oxide. Simultaneous dissolution occurred in thiourea solutions only, the threshold concentration depending upon the degree of agitation employed. In polysulphide solutions no dissolution of the sulphide film was detected.

Dynamic Jahn–Teller Effects and Magnetic Anisotropies in Aqueous Solutions and Water–Ethanol Glasses of Copper(II) Solvates and Complexes with 2,2′-Dipyridine

Dynamic Jahn–Teller effects have been recognized previously in solids which contain copper(II) ions in octahedral environments. In solutions, dynamic Jahn–Teller effects have now been observed in the EPR spectrum of the tris(2,2′-dipyridine) copper(II) complex. This is shown by the small temperature coefficient of the apparent tumbling correlation time, τc, which is associated with anisotropy contributions to the EPR linewidth and by the insensitivity of τc to variations of the solvent viscosity. In partially substituted complexes, such as the tetraaquo (2,2′-dipyridine) copper(II) species which has also been studied here, the dynamic Jahn–Teller effects are inhibited due to the inhomogeneous nature of the first coordination sphere. The possible importance of dynamic Jahn–Teller effects in homogeneous solvates of copper(II) is discussed. Evidence is presented to show that addition of ethanol to aqueous solutions of copper(II) nitrate results in the formation of inhomogeneous species.

The differential capacitance of polycrystalline copper in aqueous solution

Summary The results of measurements of the impedance of the solid copper/aqueous solution interphase for the electrolytes, NaClO4, KNO3, K2SO4, and H2SO4 are presented. The electrode is nowhere ideally polarisable. An experimentally accessible region exists from 0.25 to −0.9 V depending upon electrolyte pH. A considerable degree of interaction between hydrogen ions in solution and copper electrodes occurs in this potential region. Results suggest that H+ is absorbed in the range −0.15 to −0.35 V. The formation of a compound of copper in the range −0.6 to −0.7 V is indicated by a capacitance maximum. Hysteresis effects indicate that desorption of adsorbed species is relatively slow. In sulphate electrolytes the adsorption of the anion appears to be a further complication. It is not possible to state unequivocally the value of the p.z.c.; at best it can be placed in the range 0.0 to −0.2 V. The extent of frequency dispersion reported by previous workers is verified. It is suggested that this may be due to a frequency-dependent capacitance component connected with adsorption and desorption effects rather than dielectric relaxation or electrolyte creep.

The differential capacitance of polycrystalline copper in aqueous solution

The results of measurements of the impedance of the solid copper/aqueous solution interphase for the electrolytes, NaClO4, KNO3, K2SO4, and H2SO4 are presented. The electrode is nowhere ideally polarisable. An experimentally accessible region exists from 0.25 to −0.9 V depending upon electrolyte pH. A considerable degree of interaction between hydrogen ions in solution and copper electrodes occurs in this potential region. Results suggest that H+ is absorbed in the range −0.15 to −0.35 V. The formation of a compound of copper in the range −0.6 to −0.7 V is indicated by a capacitance maximum. Hysteresis effects indicate that desorption of adsorbed species is relatively slow. In sulphate electrolytes the adsorption of the anion appears to be a further complication. It is not possible to state unequivocally the value of the p.z.c.; at best it can be placed in the range 0.0 to −0.2 V. The extent of frequency dispersion reported by previous workers is verified. It is suggested that this may be due to a frequency-dependent capacitance component connected with adsorption and desorption effects rather than dielectric relaxation or electrolyte creep.

Synthesis of Copper(II) Complexes with Maleic Acid

Abstract Three copper(II) complexes with maleic acid, [Cu mal(H2O]) (I) (mal=C2H2(COO)2), [Cu(Hmal)2(H2O)4] (II) and [Cu2(Hmal)4]·H2mal·4EtOH (III) (EtOH=C2H5OH), were synthesized. Compound I was prepared from an aqueous solution of copper(II) sulfate pentahydrate and sodium hydrogenmaleate at room temperature as fine blue crystals. Compound II was prepared by adding little by little copper(II) hydroxide or copper(II) hydroxycarbonate to an aqueous solution of maleic acid at a temperature below 0°C in an ice-salt bath, obtaining light-blue powdered crystals. Compound III was prepared by heating a mixed alcoholic solution of maleic acid anhydride, copper(II) sulfate pentahydrate and sodium carbonate anhydride (3:1:1) in a flask with a reflux condenser for two hours. Fine bluish-green crystals were obtained. By using copper(II) hydroxide instead of copper(II) sulfate in the above preparation, a better yield can be obtained. The effective magnetic moments of I and II were 2.00 B. M. (20°C) and 1.97 B. M. (20°C), respectively, which are relatively close to the spin-only value of the divalent copper ion. On the other hand, the magnetic moment of III was subnormal, being 1.12 B. M. (18°C). The reflection spectrum of III gave a shoulder near 370 mμ, which is specific to green copper complexes. The product (IV) obtained by the thermal decomposition of I at 220°C and the product (V) obtained from II at 160°C, which are presumed to have the chemical formula [Cu-mal(H2O)0.1] and [Cu(Hmal)(mal)1⁄2], respectively, gave normal magnetic moments, 1.91 and 1.89 B. M. (20°C). However, product (VI), obtained by expelling the alcohol from III had a magnetic moment of 1.31 B. M. (17°C). Different from the corresponding copper(II) phthalate complexes, no green copper complexes having subnormal magnetic moments could be obtained through dehydration of the blue maleate complex I or the light-blue complex II having normal magnetic moments.

Certain Interactions between Transition Metal Ions and the NCS Group in Chromium(III) Isothiocyanato Complexes. I. Reinecke’s Salt Type Complexes Involving Cobalt(II) and Copper(II) Ions

Abstract Cobalt(II) tetraisothiocyanatochromate(III), Co[Cr(NCS)4(NH3)2]2, was prepared from cobalt(II) chloride and Reinecke’s salt in an aqueous solution. The absorption spectrum gave evidence that the so-called “cobalt-salt” dissociated into cobalt(II) cation and Reineck’s anion in aqueous solution. The reflection spectrum showed a remarkably strong absorption band at 14.08×1013 sec−1, which might be assigned to bonding between cobalt(II) and sulfur in an NCS− ligand. The three absorption peaks observed at 2158, 2095 and 2065 cm−1 in the IR spectrum due to C–N stretching vibrations also emphasized the strong interaction between cobalt and sulfur. The effective magnetic moment estimated was 4.58 B. M. at 18.3°C. The corresponding copper(II) salt, Cu(OH)[Cr(NCS)4(NH3)2], was obtained from an aqueous solution of copper(II) sulfate and Reinecke’s salt as a yellow powder. It was a sparingly soluble in water. In the reflection spectrum, the red-shifted band covered much of the first band region of Reinecke’s salt and in the IR spectrum, the C–N band had only a small splitting. The magnetic moment was found to be 3.84 B. M. at 16.0°C, which is close to the predicted value in the complex when copper is reduced, becoming univalent. X-Ray diffraction analysis also showed a relatively stronger contraction of the unit cell in the copper salt than in the cobalt salt. On the basis of the above points, it was proposed that in the copper salt there is considerable π-bonding between copper and the two adjacent isothiocyanate groups.

Reactions of some N,N,N′,N′-tetraalkyl-substituted diamines with concentrated aqueous solutions of copper(II) salts

Reactions of some N,N,N′,N′-tetraalkyl-substituted diamines with concentrated aqueous solutions of copper(II) salts

Spectrophotometric studies of copper (II)—bis-2-pyridyl glycol complex

An aqueous solution ofbis-2-pyridyl glycol forms a deep blue water-soluble complex with an aqueous solution of copper (II) salts. The complex has an absorption maximum at 600–650 mµ between pH range 3·0–8·7. The complex is stable for four days and obeys Lambert-Beer’s law in the concentration range of 5·08–50·80 ppm. of copper (II) in solution. The optical density of the complex remains constant between pH 3·8–5·9. The molar composition as determined by the method of continuous variation and by the slope ratio method has been found to be 1:1. The limits of interference due to some foreign ions during the estimation of copper (II) have been determined.

Oxygen-17 NMR and Copper EPR Linewidths in Aqueous Solutions of Copper(II) Ion and 2,2′-Dipyridine

Between 0° and 60°C the transverse relaxation rate of oxygen-17 nuclei in water is increased in proportion to the concentration of diaquobis (2,2′-dipyridine) copper(II) which exists in equilibrium with the tris(chelate) species in solutions of tris(2,2′-dipyridine) copper(II) nitrate. The excess relaxation rate 1 / T2p due to the presence of the paramagnetic ions is controlled by the rate of relaxation of oxygen-17 nuclei in the coordination sphere of the [Cu(dipy)2(OH2)2]+ + species where the paramagnetic electron–oxygen-17 hyperfine interaction AL / h is of the order of 1.0 × 107 Hz. This value is large in comparison with the one previously reported for diaquobis (ethylenediamine) copper(II), where the two water molecules occupy positions trans with respect to each other on the long axis of the Jahn–Teller distorted complex. The X-band EPR spectrum of an ethanol–water glass where 2,2′-dipyridine/copper(II) ratio is 2.00 indicates that the cis and the trans isomers of the diaquobis (2,2′-dipyridine) copper(II) species are present in the glass. In aqueous solutions at 24°C only one disubstituted species can be observed in the EPR spectrum. It is assumed that this spectrum is predominantly due to the cis-diaquo isomer which may exist in equilibrium with small amounts of the trans isomer. Lower limits of the electron spin–lattice relaxation times and the apparent tumbling correlation times at 25°C were obtained from the X-band EPR spectra for the tetraaquo (2,2′-dipyridine), the diaquobis (2,2′-dipyridine), and the tris-(2,2′-dipyride) copper(II) species. The tumbling correlation time for the latter species is unusually low. It is proposed that the phenomenon can be explained by applying the previously discussed concept of the dynamical Jahn–Teller effect to complex ions in aqueous solutions.

Photopotential Measurements During Corrosion of Copper in Aqueous Solutions

Abstract Photopotentials of single crystal copper immersed in water and sodium halide solutions have been measured. Experimental results indicated that cuprous oxide formed on copper immersed in water. In sodium halide solutions, cuprous oxide was formed initially, followed by the formation of the cuprous halide film after prolonged immersion. Observed transient and steady-state photo-potentials were attributed to the effect of light on barrier junctions at resulting metal-semiconductor film-electrolyte interfaces. According to the Williams model for thephotogalvanic or “Becquerel” effects of binary semiconductor-electrolyte systems, the positive valued photopotentials of copper in water, sodium bromide and sodium iodide solutions indicated that the cuprous oxide, cuprous bromide and cuprous iodide films formed on copper in the respective solutions were p-type semiconductors. Negative photopotentials observed for copper in sodium chloride and sodium fluoride solutions suggest that cuprous chloride and cup...

Absorption Spectra of Cobalt (II) Chloride in concentrated perchlorate solutions

AbstractThe pink color of an aqueous solution of cobalt(II) chloride changes into reddish violet with the addition of a large amount of sodium perchlorate, and the resulting solution exhibits a remarkable thermochromism, becoming bluish even by slight heating. Spectral data on these color changes are given and discussed from the point of view that the decrease of water activity caused by the added inert salt favors the formation of chlorocomplexes. A similar effect of sodium perchlorate was also observed in aqueous solutions of copper(II) and nickel chlorides.

Substituted benzoic acid complexes of copper(II)

Solutions of p-cyano, p-fluoro, p- and m-hydroxy-benzoic acids in ehtanol react with aqueous solutions of copper- (II) aceetate to yield complexes of empirical formula [Cu(X-C 6H 4CO 2)(OH)]. The use of similar reaction conditions for p-chloro-, p-bromo-and p-iodo-benzoic acids affords ethanol adducts of the corresponding copper benzoates, Cu(X-C 6H 4CO 2) 2.C 2H 5OH. The latter compounds display subnormal magnetic moments and antiferromagnetism similar to that noted for copper acetate monohydrate. The presence of analogous binuclear structural species is proposed. On the basis of the normal moments and infrared spectral evidence, it is suggested that the complexes containing hydroxy groups are composed of polymeric hydroxide-bridged structural units. The magnetic behavior of these derivatives has been related to previously experienced difficulties in correlating the magnetic susceptibilities of copper(II) salts of substituted benzoic acids with the substituents on the phenyl ring.

New method for the spectrophotometric determination of ultramicro amounts of copper

A deep yellow colour is formed by the reaction with phenol and chloramine-T in the presence of copper, and this reaction is used for the photometric determination of copper. An aqueous solution of copper and the reagents at pH 11.5–11.6 is heated. The molar absorptivity at 410 mμ, is 2.32 × 10 6. The method has been used satisfactorily to determine ultram amounts of copper in high-purity silicon.

Radiation-induced Oxidation of Cytosine and Uracil in Aqueous Solution of Copper (II)

BOTH the hydrated electron, e−aq, and the hydroxyl radical, OH, which are formed as the principal intermediates in water radiolysis, react rapidly with the pyrimidine bases through preferential addition to the 5, 6 double bond to give the hydropyrimidyl radical, BH, and the hydroxypyrimidyl radical, BOH, respectively1–4. The yields for base destruction (molecules/100 eV) in oxygen-free solutions under γ-rays are, however, consistently low, G(−B) ⩽ 1 (refs. 5 and 6), when compared with primary yields of the radical species derived from water, Ge−aq = 2.85, GOH = 2.4 (ref. 7); recent work indicates that secondary reactions of BH and BOH lead to regeneration of the parent compound4. In oxygen-saturated solutions, e−aq, is scavenged by oxygen to form O−2(HO2), the regeneration reaction is quenched, and the yield for base destruction increases to G(−B)∼2 through reactions involving the peroxy radical, B(OH)⨀2. Many organic products are formed, however, from the intermediate, B(OH)⨀2, and the overall product stoichiometries have yet to be fully elucidated8.

A new reaction for the identification and determination of perchlorate : Part I. Detection of perchlorate

Perchlorate is extracted into methyl isobutyl ketone from aqueous solutions of copper(II) ions containing azide ions and an excess of 2,2'-dipyridyl. The yellow color of the organic phase can be used for the detection of perchlorate. A procedure is given which allows the identification of 3 μg of perchlorate. Considerably larger amounts of nitrate, chlorate, chloride and several other anions can be tolerated. By performing the test with the help of the Weisz ring oven technique, a limit of identification of 0.15 μg of perchlorate can be attained.

Determination of copper in sea water by atomic absorption spectroscopy

A commercial atomic absorption spectrophotometer is used without modification to establish the most suitable operating conditions for the determination of copper. Using the direct method of spraying aqueous solutions of copper into the flame, the minimum copper which can be determined is about 25 μg/litre. However, this method is not suitable for determining copper in sea water. A method based on the extraction of the copper-ammonium pyrrolidine dithiocarbamate complex into ethyl acetate and spraying of the organic extract into the flame is satisfactory, and it gives a marked increase in sensitivity.

Kinetics and Mechanism of Copper Dissolution in Aqueous Ammonia

AbstractThe dissolution of copper in aqueous solutions of ammonia is a corrosion process in which the cathodic reaction is the reduction of oxygen at the surface of the metal according to: and the anodic reaction is the oxidation of copper according to: Superimposed with these reactions is the cuprous‐cupric equilibrium: A theoretical derivation of the velocity equation of the dissolution process has been obtained, which describes quantitatively the experimental facts. The equation is as follows: where k1, k2, k3 and f are constants, A is the surface area of the metal in contact with the aqueous phase and [O2], [NH3] and [Cu2+] are oxygen, ammonia and cupric ion concentrations respectively.

An investigation of the chelatometry of Cu II with ethylenediamine- N, N', N', N- tetra-n-propionic acid

A selective new polyaminocarboxylic acid-metallochromic indicator system is proposed for the accurate and interference-free titration of copper in aqueous solution in the presence of other metals such as Pb, Zn, Cd, Al, Mg, Ca, Ba, Sr, etc. No separations or addition of masking agents are necessary in this procedure. Nickel interferes only slightly.

Determination of the solubility product of CuS in a gel employing the liesegang phenomenon

The solubility product of CuS in a 3% agar gel has been determined by a technique involving the formation of Liesegang bands. Aqueous solutions of copper (II) and sulfide ions are allowed to diffuse towards one another from opposite ends of a length of gel. The rate of growth of the first (and only) band is followed chemically, and the time corresponding to zero moles of CuS after beginning of diffusion is determined by a simple extrapolation. This value, along with the band position, is substituted into an appropriate solution of Fick's Second Law for each diffusion species, and the concentration product is formed. The value is within the range of values for the K sp, of CuS in water as reported in the literature. Assumptions are discuseed, as are limitations and generality of the method.