Solutions Of Different Composition Research Articles

Effect of sodium substitution by yttrium on the structural, dielectric and electrical properties of Ba2Na(1-3x)YxNb5O15 ceramics

The effects of Na+ substitution by Y3+ on the structural, microstructural, dielectric and electrical properties of Ba2Na(1-3x)YxNb5O15 compositions with (x = 0, 0.02 and 0.04) have been studied in detail. The solid solutions of different compositions were prepared by the solid state reaction route method and characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Complex Impedance Spectroscopy (CIS) techniques. The XRD study confirmed that all prepared compositions have a single-phase orthorhombic tungsten bronze structure with space group Cmm2 at room temperature. The microstructural studies revealed a grain shape and size change in response to increasing Y3+ concentration. The dielectric properties of the obtained compositions are evaluated over a temperature range of 40–600 °C. The dielectric properties were improved for the Y2O3-substituted Ba2NaNb5O15 compound compared to the undoped Ba2NaNb5O15 compound. The non-Debye type relaxation mechanism is confirmed by the -Z″ versus Z′ traces. The grain contribution was studied using an equivalent electrical circuit with a Resistor R, a Capacitor C, and a Constant-Phase Element CPE in parallel, in the absence of the grain boundary response and the electrode effect in the frequency range 10 Hz-1MHz. The experimental AC conductivity data were evaluated by using Jonscher's power law. The activation energies obtained from the relaxation and conduction processes, present two different regions as a function of temperature related to the two electrical processes for the prepared ceramics.

An Optical Fiber Sensor for Uranium Detection in Water.

An optical sensor for uranyl has been prepared based on a gold-plated D-shaped plastic optical fiber (POF) combined with a receptor consisting of a bifunctional synthetic molecule, 11-mercaptoundecylphosphonic acid (MUPA), with a phosphonic group for complexing the considered ion, and a sulfide moiety through which the molecule is fixed at the gold resonant surface as a molecular layer in an easy and reproducible way. The sensor is characterized by evaluating the response in function of the uranyl concentration in aqueous solutions of different compositions and real-life samples, such as tap water and seawater. The mechanism of the uranyl/MUPA interaction was investigated. Two different kinds of interactions of uranyl with the MUPA layer on gold from water are observed: a strong one and a weak one. In the presence of competing metal ions as Ca2+ and Mg2+, only the strong interaction takes place, with a high affinity constant (around 107 M−1), while a somewhat lower constant (i.e., around 106 M−1) is obtained in the presence of Mg2+ which forms stronger complexes with MUPA than Ca2+. Due to the high affinity and the good selectivity of the recognition element MUPA, a detection limit of a few μg L−1 is reached directly in natural water samples without any time-consuming sample pretreatment, making it possible for rapid, in situ controls of uranyl by the proposed sensor.

Characteristics investigation of composite electrochromic films based on Ni(Oh)2, polyvinyl alcohol, and polyvinylpyrrolidone

The cost of electrochromic “smart” windows ranges from 200–800 USD/m2. The high cost is determined by the small volume of production and the high cost of vacuum methods for applying device layers. The development of other methods could lead to lower costs and further mass use of “smart” windows. The paper presents the work on improving the electrochemical method of deposition of electrochromic films based on Ni(OH)2. Composite electrochromic films were deposited from Ni(NO3)2 solutions with the addition of water-soluble polymers – polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and mixtures thereof. Two PVA grades and one PVP grade were used in the experiments. As a result, six films were obtained from solutions of different compositions and concentrations of polymers. An investigation of the optical properties of the films in the initial state showed that there is no intense absorption of light in the entire visible spectrum and the transmission corresponds to a glass substrate. Thus, the formed electrochromic films will not produce tints and visible light absorption in the finished electrochromic element. The electrochemical and electrochromic characteristics of the films differed significantly depending on the amount and specific polymers used. The film obtained from a solution containing PVA grade 24-99 was the most electrochemically active, while the best electrochromic characteristics were in the film deposited from a solution of a mixture of PVP grade 24-99 and PVP. Moreover, the films obtained in solutions containing separately PVA grade 24-99 and PVP had worse electrochromic characteristics, and the electrochemical characteristics were the same or worse relative to the film obtained in a mixture of polymers. The results of the method of electrochemical impedance spectroscopy showed compliance with the found electrochromic and electrochemical characteristics of the formed films.

Primena kiselinskih obrada u cilju poboljšanja karakteristika kolektor stena

During the exploitation life of one tray, different influences cause damage to the rocks located in the borehole. Damaged rocks are characterized by the clogging of the hard space, which is manifested by reduced bandwidth, resulting in a decline in fluid production. In order to solve this problem, there are different stimulating methods that are successfully applied around the world. In Serbia, there is a practice that acid treatments are most commonly used when solving the problem of rock damage. These methods are based on the application of acid solutions of different composition, depending on the mineral composition of the rock collector. This paper describes the process of resolving the reduction of production of X-1 and X-2 wells, whose production intervals are represented by rocks with different carbonate content , and the problem-solving approach is different.

Digestion Efficiency during Alkaline Persulfate Oxidation for Determination of Total Phosphorus Content of Biological Samples.

Quantifying total phosphorus contents of organisms can elucidate their physiological condition and the nutrient cycles of ecosystems. Simple, brief, and safe persulfate oxidation methods have been used for total P determination, but oxidizing solutions of different compositions and volumes have been used. Two certified reference materials were used to evaluate digestion efficiencies of different solutions for this study. Although the phosphorus recoveries were low (<90%) without NaOH, phosphorus recoveries using the solution with 4% K2S2O8 and 0.15 M NaOH were complete. Results demonstrated that digestion efficiency depends on the K2S2O8 concentration and on the pH condition. Moreover, the phosphorus recoveries were achieved at >4 mL/mg solution/material ratios for both standard materials. Therefore, the author recommends using >4 mL of the 4% K2S2O8 solution with 0.15 M NaOH for sample materials of <1 mg to quantify the total phosphorus of biological samples.

PSXV-11 Using assisted reproductive technologies for obtaining new breeding forms by hybridization in sheep breeding

Abstract Arctic and northern latitudes are rarely used in animal husbandry, meanwhile, wild species of animals that are best adapted to the harsh climate successfully live in these territories. The aim of the study was to obtain new breeding forms in sheep using assisted reproductive technologies. Domestic sheep of the Buryat Coarsewool and sperm from 4 Siberian bighorn sheep of the Yakut population (Ovis nivicola lydekkeri) were used. Methods of postmortal removal of viable semen from epididymal aspirate and also the composition of a newly created extender for freezing epididymal semen have been developed. Thirteen sheep were inseminated using laparotomy. Sheep in estrus were identified by a test ram. The viability of the semen is influenced by the time interval from the moment of death to the removal of the semen from the epididymal aspirate. The temperature of the environment in which the testicles were kept before the semen removal also affects the final quality of the sperm. Thus, the highest viability of epididymal semen was observed at t = + 4°C when removed within 2 hours after the ram` death. As a result of research, the optimal composition of the extender was developed from test solutions of different compositions. The viability of spermatozoa for the extender was 25–30% higher than in others. Since the fertilizing properties of epididymal semen are lower than that of ejaculated semen, we used the intratubal insemination method. As a result, 8 hybrid F1 offsprings (1/2 domestic sheep x 1/2 wild bighorn sheep) were obtained, which can be kept year-round in winter pastures in the conditions of extremely low temperatures.

The effect of osmotic dehydration before drying on the physicochemical and sensorial characteristics of dried onion slices

The effect of osmotic dehydration before drying on the physicochemical and sensorial characteristics of dried onion slices

Ultrastructural changes in the spinal cord of rats with experimental allergic encephalomyelitis under the influence of human umbilical cord-derived multipotent mesenchymal stromal cells cryopreserved according to different protocols

The transplantation of multipotent mesenchymal stromal cells (MMSCs) is considered to be a possible therapy of multiple sclerosis. For the clinical application of human umbilical cord-derived MMSCs (UC-MMSCs) it is necessary to develop a method of their cryopreservation taking into account the type of cryoprotective media and to investigate the possibility of using these cells for therapeutic purposes in vivo. The purpose of the study was to investigate the effect of UC-MMSCs, cryopreserved in solutions of different composition, on the processes of demyelination and remyelination of the spinal cord of rats with experimental allergic encephalomyelitis (EAE) as a model of multiple sclerosis. Materials and methods. The EAE was modeled by subcutaneous administration of homogenized spinal cord of adult rats with complete Freund's adjuvant. On the 18th day rats with moderate relapsing-remitting form of EAE were suboccipitally injected 1•106 UC-MMSCs, cryopreserved in cryoprotective media containing dimethyl sulfoxide (DMSO), fetal bovine serum (FBS), ethylene glycol, trehalose and sucrose at different composition. On the 35th and 60th days, the studies of ultrastructural changes of the lumbar spinal cord (L3-L5) were performed, assessing the degree of demyelination of nerve fibers by the ratio of myelin sheath (MS) thickness to the diameter of the axis cylinder (AC) of axons. Results. In rats with moderate EAE from the 35th to the 60th day after the modelling of the disorder, destructive changes and signs of demyelination in the spinal cord increased; the MS/AC index corresponded to the average degree of axon demyelination. Suboccipitally administered cryopreserved UC-MMSCs to EAE rats, depending on the used cryopreservation solution, slowed or stopped the demyelination, decreased the MS/AC index to a low degree of axonal demyelination. Reducing the concentration of DMSO in the cryopreservation medium from 10 % to 4 % and adding 6 % trehalose provided a better effectiveness of UC-MMSCs in decreasing the degree of demyelination in EAE. At the same time, the standard solution (10 % DMSO, 90 % FBS) provided these effect, but to a lesser extent. The use of a multicomponent cryopreservation medium containing 15 % ethylene glycol, 3 % DMSO, 10 % sucrose, 12 % trehalose and 60 % FBS did not achieve the goal of maintaining the effects of UC-MMSCs to reduce the degree of demyelination in EAE. Conclusions. To maintain the therapeutic properties of UC-MMSCs, it is advisable to add a reduced concentration of DMSO (4 %) and 6 % trehalose to the cryopreservation medium, supplemented with 90 % fetal bovine serum.

Potentiometric, thermodynamics and coordination properties for binary and mixed ligand complexes of copper(II) with cephradine antibiotic and some N- and O-bound amino acids (α-alanine and β-alanine)

As a model for forecasting the ligand properties of antibiotics in living organisms, formation equilibria of binary and ternary Cu(II) complex with Cephradine (Cep) antibiotic in presence of α-alanine (α-Ala) and β-alanine (β-Ala) amino acids have been studied using the potentiometric titrations. Many factors were investigated like the formation constant, protonation constant, composition and stabilities of the species formed with copper(II) ions in water and water-ethanol solutions of different compositions. The thermodynamics were calculated and the data clarified. The pH-titrations of the reaction mixtures have been revealed 1:1:1 (Cu:Cep:amino acid (AA)) ternary complex formation. By aid of Δ log10K, Δ log10β and log10X parameters, quantitative matching of the stability of mixed-ligand complexes and the stability of the binary complexes was done. Investigations of the stability of the ternary complexes relative to their corresponding binary complexes indicated that formation of ternary complexes is more preferable than binary metal complexes. The obtained data from protonation of the investigated cephradine antibiotic and β-Ala/α-Ala amino acids and their complex formation equilibria will be a significant contribution to workers carrying out mechanistic studies in biological media.

Nanofiltration of solutions containing organic and inorganic salts: Relationship between feed and permeate proportions

Nanofiltration can be considered for the purification of valuable products obtained by fermentation, like organic acids. In this work, nanofiltration experiments are carried out with synthetic solutions of different compositions containing acetate (Ac), propionate (Pr), and butyrate (Bu), as well as inorganic salts (NaCl). Although the retention of charged solutes can be significantly modified according to the composition of the solution, it is observed that there is a filtration flux above which the solutes proportions in the permeate remain constant. These proportions do not depend on the total concentration but only on the solutes proportions in the feed. Finally, individual solute transfer is found to vary linearly with the total solute flux. Similar trends are observed with two NF membranes despite their different properties.

HYDROGEN ROLE IN SELECTIVITY OF SUBSTITUTED NITRO-AZOBENENES HYDROGENI-ZATION ON SKELETAL NICKEL IN 2-PROPANOL AQUEOUS SOLUTIONS

Elucidation of the substituted nitrobenzenes transformations sequence, in particular, containing several reactive groups and the development of approaches to the control of the selectivity of processes involving them is of interest from both theoretical and practical points of view. The article is devoted to the analysis of the hydrogenation kinetics of 2-nitro-2'-hydroxy-5'-methylazobenzene, 4-nitro-2'-hydroxy-5'-methyl-isobenzene, 4-nitroaniline, 4-amino-2'-hydroxy-5'-methylazobenzene on skeletal nickel in 2-propanol aqueous solutions of different composition, including with the addition of acetic acid or sodium hydroxide with various initial amounts of organic compound. The rise in the 4-nitro-2'-hydroxy-5'-methylazobenzene initial amount leads to increase in the nitro group transformation rate in the starting compound and to decrease in the azo-group transformation rate. The effect of sodium hydroxide additives in the 2-propanol aqueous solution on the nitro- and azo-groups conversion rate into 4-nitro-2'-hydroxy-5'-methyl-isobenzene is analogous to the change in the individual compounds hydrogenation rates (4-nitroaniline and 4-amino-2'-hydroxy-5'-methylazobenzene). Obtained results do not contradict the parallel-sequential scheme concept for the 4-nitro-2'-hydroxy-5'-methylazobenzene transformations. One of the directions is associated with the azo-group transformation into 4-nitro-2'-hydroxy-5'-methylazobenzene and 4-nitroaniline and 2-amino-4-methylphenol formation, and the second with the 4-nitro-2'-hydroxy-5'-methyl-isobenzene conversion through 4-amino-2'-hydroxy-5'-methyl-isobenzene by the nitro-group reducing. At the reaction end, all intermediate compounds are reduced to 2-amino-4-methylphenol and 1,4-phenylenediamine. When 2-nitro-2'-hydroxy-5'-methylazobenzene is hydrogenated, one of the directions leads to the 2-nitro-2'-hydroxy-5'-methylhydrazobenzene formation, and the second to the product containing the triazole cycle - N-oxide 2-2'-hydroxy-5'-methylphenylbenzotriazole. At the reaction end, these compounds are reduced to 2-2'-hydroxy-5'-methylphenylbenzotriazole and 2-amino-4-methylphenol and 1,2-phenylenediamine, respectively. In the solution at the sodium hydroxide presence, 2-nitro-2'-hydroxy-5'-methylhydrazobenzene transforms into the N-oxide 2-2'-hydroxy-5'-methylphenylbenzotriazole as a result of intramolecular rearrangement.

K.V. Chmutov’s Legacy in Developing the Fundamental Concepts of the Radioactive Elements Chromatography

A review is presented of the work performed from the early 1950s to the present at the Laboratory of Radioelement Chromatography of the USSR Academy of Sciences’ Institute of Physical Chemistry (the Russian Academy of Sciences’ Frumkin Institute of Physical Chemistry and Electrochemistry). The works in the field of studying the patterns of sorption and dynamics of chromatography for systems of chelate displacement chromatography (CDC), the chromatographic separation of elements under conditions of ionizing radiation, and the chromatographic separation of radionuclides with the use of separating ions are described. The separation of 137Cs radionuclide from irradiated nuclear fuel (INF) reprocessing solutions using ferrocyanide sorbents, the use of ion-exchange resins for the recovery of rare-earth elements (REEs) and actinides from solutions of different composition, and advances in the field of the sorption purification of liquid radioactive wastes of different chemical and radionuclide composition are also considered. The means developed at the Laboratory provided the basis for the technologies of the separation of radioactive elements from INF reprocessing solutions and the purification of liquid radioactive wastes. These technologies are used today at enterprises of the Rosatom State Atomic Energy Corporation, nuclear power stations, and other facilities of the nuclear industry.

Needleless Electrospinning of a Chitosan Lactate Aqueous Solution: Influence of Solution Composition and Spinning Parameters

The biological activity of chitosan determines its broad application as a biopolymer for non-woven wound dressings fabricated by electrospinning. The electrospinning process is affected by a large number of different factors that complicate its optimization. In the present work, the electrospinning of chitosan lactate was carried out using a needleless technique from water solutions of different compositions. Surface response methodology was used to evaluate the effects of the concentration of chitosan, polyethylene oxide, and ethanol on solution properties, such as viscosity, surface tension, and conductivity, as well as the process characteristics and fiber quality. The viscosity of the spinning solution is determined by the polymer concentration as well as by the interpolymer interactions. The addition of ethanol to the spinning solutions effectively decreases the solution surface tension and conductivity, while increasing the volatility of the solvent, to provide more intense fiber spinning. Atomic force microscopy revealed that the chitosan lactate fibers were obtained without defects and with a narrow thickness distribution. The spinning parameters, voltage, distance between electrodes, and rotation speed of the spinning electrode had insignificant influences on the fiber diameter during needleless electrospinning.

Lithium Occurrences in Brines from Two German Salt Deposits (Upper Permian) and First Results of Leaching Experiments

Lithium occurrences were detected in Upper Permian (Zechstein) salt rocks and saline solutions of the Gorleben and Morsleben salt structures, northern Germany. The brine occurrences were mainly connected to anhydrite rock-bearing formations and to lithological boundaries. Most of these brines display a high Mg content and were accordingly interpreted as intrasalinar solutions, which developed during sedimentation, diagenesis, and the subsequent rock–fluid interaction. These Mg-rich brines frequently show high Li concentrations. One of the assumptions made, is that Li was leached from phyllosilicates, since no natural Li-bearing salt minerals are known to date. To improve the understanding of the origin of Li in the brines, leaching experiments were performed on the Li-bearing phyllosilicate Lepidolite. Lepidolite with a Li content of 2.42 wt. % served as an analogue material, which was exposed to 18 saline solutions of different composition for a period of three years. The most pronounced leaching effect (53.36 µg Li/g in the brine) was observed during the interaction with a 0.03 mol/kg H2O MgCl2 solution, the second most pronounced by modern seawater interaction. The experiments show that the amount of Li leached from the lepidolite is dependent on brine composition.

Application of polarization measurements for current efficiency calculation

The paper considers a method used to determine Faraday current efficiency (CeF) based on the ratio of partial currents of metal and hydrogen reduction. To calculate the Faraday current efficiency based on polarization measurements, it is necessary to know the working current density and potential (Ei) at which the metal is deposited in the corresponding solution, as well as kinetic parameters of hydrogen evolution for determining the partial current density of hydrogen (iН2 ) at this potential. The proposed method was used to calculate current efficiency for the processes of nickel extraction and nickel coating application from solutions containing nickel sulfate at current density of 300 A/m2. The study allowed to determine kinetic parameters of hydrogen evolution by the polarization curve obtained in the background electrolyte solution containing 120 g/l of magnesium sulfate and 18 g/l of boric acid at pH = 3.9. An equation was obtained to calculate the partial current density of hydrogen evolution at any potential by kinetic parameters. The use of kinetic regularities made it possible to calculate nickel CeF in sulphate solutions of different composition and with different pH values (3.0 and 4.1). The calculated CeF values within the margin of error coincide with the current efficiency value determined by the gravimetric method using a copper coulometer. It is shown that the division of the «total current efficiency» (CeΣ), which is a commercial indicator, into Faraday (CeF) and apparatus (Ceap) indicators in combination with the method using partial polarization provide additional information about the degree of process perfection.

Examination of the Capabilities of Metalorganic Vapor-Phase Epitaxy in Fabrication of Thin InAs/GaSb Layers

The capabilities of metalorganic vapor-phase epitaxy (MOVPE) in fabrication of structures with thin (1–2 nm) alternating InAs/GaSb layers on a GaSb substrate are studied. The characteristics of these structures were examined using transmission electron microscopy and methods of photo- and electroluminescence. It was found that two GaInAsSb solid solutions of different compositions were formed in the active regions of structures in the given growth conditions. The fabricated system was characterized by an emission wavelength of 4.96 μm at a temperature of 77 K. The results reveal new opportunities for bandgap engineering of semiconductor structures based on InAs/GaSb, which are designed for optoelectronic devices operating in the infrared range, provided by MOVPE.

SYNTHESIS AND ELECTRICAL CONDUCTIVITY OF SOLID SOLUTIONS OF THE SYSTEM RbF-PbF2-SnF2

In the system RbF–PbF2–SnF2 are formed solid solutions of the heterovalent substitution RbxPb0,86‑xSn1,14F4-x (0 &lt; x ≤ 0,2) with structure of β–PbSnF4. At x &gt; 0,2 on the X-ray diffractograms, in addition to the basic structure, additional peaks are recorded that do not correspond to the reflexes of the individual fluorides and can indicate the formation of a mixture of solid solutions of different composition. For single-phase solid solutions, the calculated parameters of the crystal lattice are satisfactorily described by the Vegard rule. The introduction of ions of Rb+ into the initial structure leads to an increase in the parameter a of the elementary cell from 5.967 for x = 0 to 5.970 for x = 0.20. The replacement of a part of leads ions to rubium ions an increase in electrical conductivity compared with β–PbSnF4 and Pb0.86Sn1.14F4. Insignificant substitution (up to 3.0 mol%) of ions Pb2+ at Rb+ at T&lt;500 K per order of magnitude reduces the conductivity of the samples obtained, while the nature of its temperature dependence is similar to the temperature dependence of the conductivity of the sample β-PbSnF4. By replacing 5 mol. % of ions with Pb2+ on Rb+, the fluoride ion conductivity at T&gt; 450 K is higher than the conductivity of the initial sample Pb0,86Sn1,14F4 and at temperatures below 450 K by an order of magnitude smaller. With further increase in the content of RbF the electrical conductivity of the samples increases throughout the temperature range, reaching the maximum values at x≥0.15 (σ573 = 0.34–0.41 S/cm, Ea = 0.16 eV and σ373 = (5.34–8.16)•10-2 S/cm, Ea = 0.48–0.51 eV, respectively). In the general case, the replacement of a part of the ions of Pb2+ with Rb+ to an increase in the electrical conductivity of the samples throughout the temperature range. The activation energy of conductivity with an increase in the content of RbF in the low-temperature region in the general case increases, and at temperatures above 400 K is inversely proportional decreasing. The nature of the dependence of the activation energy on the concentration of the heterovalent substituent and its value indicate that the conductivity of the samples obtained increases with an increase in the vacancies of fluoride ions in the structure of the solid solutions.

Thermodynamic and experimental modeling of the formation of the mineral phase of calcification

Vascular calcification is the process of calcium salt precipitation in vessel walls. In-depth understanding of the mechanisms of crystallization of calcifications in blood vessels is crucial for developing effective protective therapy. Calcification processes reduce the life span of implanted heart valves. The purpose of this paper is a comprehensive study of calcification processes. We calculated the solubility diagrams of the basic poorly soluble compounds formed in the prototype human plasma, performed laboratory modeling of crystallization of calcification mineral phases under conditions typical of human blood plasma solution (ionic composition, pH), and verified the obtained theoretical and experimental modeling results for adequacy to pathogenic phase formation from human blood plasma solution. The paper presents the results of the thermodynamic calculation of the formation of calcification mineral phases and experimental results of phase formation under conditions typical of the human blood plasma prototype. The laboratory tests showed that dopants of the biological solution (magnesium ions and glutamic acid) affect phase composition and solubility of the samples. The bioactivity of synthetic samples was studied in solutions of different composition and in Verapamil. The results indicate that the model studies of the crystallization of pathogenic formations in the cardiovascular system performed to identify the mechanisms that control their genesis are significant and will provide timely diagnosis of calcification and development of new approaches in cardiology aimed to reduce the incidence of these diseases. Statement of significanceThe processes of crystallization of organo-mineral associations (OMA) that are part of the physiogenetic (bone, teeth) and pathogenic minerals (urinary, dental, calcifications etc.) are currently one of the crucial study areas. These studies are of essential interest since pathogenic OMA are primarily considered to be human diseases, for example, arteriosclerosis, which is associated with precipitation of calcium salts in blood vessels. It is the second most common disease after atherosclerosis among all lesions of arterial vessels. It should be noted that the percentage of calcification in blood vessels, heart valves and operating stents has increased in recent years.Vascular calcification is a complex process that involves a number of mechanisms responsible for the precipitation of calcium salts in vessel walls. As a result, arterial stiffness and pulse wave velocity increase, which in turn increases the rate of morbidity and mortality from cardiovascular diseases. The study and in-depth understanding of the mechanisms of calcification crystallization in blood vessels can be crucial for developing effective protective therapy.

New Cyanide-Free Alkaline Electrolyte for the Electrodeposition of Cu-Zn Alloys Using Glutamate as Complexing Agent

Glutamate is a potential replacement of cyanide in alkaline electrolytes due to its capability to form complexes with bivalent metal ions. Since promising results were achieved with copper and zinc plating baths, and the use of cyanide implies environmental and safety disadvantages, it was decided to study the possibility of codepositing these two metals using sodium glutamate as complexing agent. Electrochemical processes involved in electrodeposition of copper and zinc individually as well as in solutions containing both metal ions were studied utilising cyclic voltammetry. Cu-Zn deposits obtained at different current densities from solutions of different composition were characterized by SEM and EDS. It was concluded that the system has a normal behavior, according to Brenner's classification, since the more noble metal is deposited preferentially. The plating bath containing 30% molar of Cu2+ was selected to continue the studies of the system.

Growth and Study of Properties of Mixed Crystals (NH4)2NixCo1 –x(SO4)2 · 6H2O

Mixed crystals (NH4)2NixCo1 –x(SO4)2 · 6H2O have been grown from aqueous solutions of different compositions by reducing the solution temperature in two growth regimes: static and dynamic. The optical characteristics of crystal samples are analyzed, the dehydration temperatures are measured, and the defect structure of the crystals is studied.