Sulfuric Acid Sulfate Research Articles

Numerical modeling of radiation-induced reactions: Fricke dosimeter at 298 K, 198 K, and 77 K

The Fricke dosimeter is a widely used gamma radiation dosimetry system. The system is based on the detection of Fe2+ to Fe3+ oxidation in an aqueous solution of ferrous sulfate in sulfuric acid, exposed to ionizing radiation in the presence of oxygen. The system is formed by a series of highly dependent chemical reactions. We developed a numerical model of coupled differential equations based on the mass balance; each equation incorporates information about the formation and breakdown of each molecule, as well as a term that represents an external source of radiation. The numerical model can reproduce the behavior of the experimental data at room temperature. We proposed a correction factor to simulate the behavior of the dosimeter at temperatures of 198 K and 77 K, respectively, when the system is in a thermal bath of dry ice or liquid nitrogen. This model could support a variety of experimental challenges for radiation at low temperatures in different fields of industry and could have relevance for astrobiology problems by offering the possibility of simulating reactions in comets and other exoplanetary bodies.

Visualization of the natural convection heat transfer of two heating spheres varying horizontal and vertical pitches

Natural convection heat transfer of two heating spheres was investigated varying the horizontal and the vertical pitches. Based on the analogy concept, mass transfer experiments were carried out by adopting a copper sulfate-sulfuric acid (CuSO4-H2SO4) electroplating system. The sphere diameter was varied from 6 to 40 mm, which correspond to Grd of 9.10 × 103–2.70 × 106. The heat transfer of two spheres for both in-line and staggered arrangements under laminar and turbulent flow conditions were analyzed by four distinct effects: stagnant, preheating, initial velocity and chimney-like effects. The heat transfer of upper sphere was either enhanced by the initial velocity effect or impaired by the preheating effect. Notable observations were that the heat transfer of lower sphere was also affected by the stagnant flow and chimney effects due to the existence of the upper sphere. This was evidenced by the visualization of the local heat transfer by copper plating pattern.

RESULTS OF X-RAY PHASE AND IR-SPEC ASE AND IR-SPECTRAL AN TRAL ANALYSIS OF AZOSUPERPHOSPH OSUPERPHOSPHATES OBTAINED ON THE BASIS OF AINED ON THE BASIS OF PHOSPHORITES OF CENTRAL KIZILKUM

This article is devoted to the use of ammonium sulfate in the production of nitrogen-phosphorus fertilizers, which are widely used in agriculture today. In the research work, the possibilities of obtaining azo superphosphate are described in detail by the use of intensive technology based on low-grade phospharites of the Central KyzylKum. X-ray and IRspectroscopic analyzes of a new type of NP-complex fertilizers obtained using a solution of ammonium sulfate in sulfuric acid are described in detail. The X-ray analysis of the obtained sample on the X-ray diffraction pattern of the azo-superphosphate fertilizer revealed the appearance of peaks in the interplanar spacing line (NH4)2SO4 of ammonium sulfate and NH4Н2РO4 of ammonium dihydrogen phosphate. It has been substantiated that in addition to the main nutrient components dicalcium phosphate and monocalcium phosphates, the sample also contains (NH4)2SO4 and NH4Н2РO4. The results of IR spectroscopic analyzes show that the process of decomposition of the CO3 2-ion in the composition of phosphorites, peaks with high intensity formed by stretching vibrations, in the regions of 873.75 and 1417.68 cm-1, were not detected in the IR spectra of the obtained sample and this proves that that the complete decomposition process is complete. Also, the formation of stretching vibrations of the H2PO4-ion - 1215.15 cm-1, the PO4 3-ion - 532.35 cm-1 and bending vibrations of the H2PO4 -ion - 1033.85 cm-1 in the IR spectrum of the sample in this NH4Н2РO4 sample and the formation of stretching vibrations of SO4 2-ion 1436.97 cm-1 confirmed the presence of (NH4)2SO4.

Process Design to Obtain Copper Sulfate Crystals Using Solid–Liquid Equilibrium of Copper Sulfate–Sulfuric Acid–Seawater

In Chile, there are several mining companies that crystallize copper sulfate pentahydrate using freshwater; however, it would be interesting to know the effect of seawater in the process design of copper sulfate pentahydrate crystals, considering the low freshwater availability in the mining zones. In the present work, three different processes are proposed for obtaining copper sulfate pentahydrate crystals using seawater, by means of the addition of sulfuric acid. These were evaluated and compared in terms of their mass and energy balances. The first process (Case 1) is composed of crystallization, heating/mixing, recrystallization, centrifugation, and drying stages. In the second process (Case 2), the recirculation of the solution from the recrystallization to the crystallization stage is added. In the third process (Case 3), the heating/mixing and recrystallization stages are eliminated, considering one crystallization stage along with centrifugation and drying. The results of the Mass and Energy balances showed that there is high energy consumption associated with the heating/mixing and recrystallization stages, so the process that does not contain these stages (Case 3) is the most convenient from an energy point of view. On the other hand, the results indicated that the highest yield (97.17%) of the process is obtained when the recirculation of the solution is added from the recrystallization to the crystallization stages (Case 2), followed for the yield of 94.41% obtained in the process where the heating/mixing and recrystallization stages are eliminated (Case 3), which would make it the most convenient process from an energy and production point of view.

Effect of Parameters of Pulse Electrolysis on Electrodeposition of Copper–Tin Alloy from Sulfate Electrolyte

The effect of pulsed electrolysis on the electrodeposition of Cu–Sn alloy from the sulfate–sulfuric acid electrolyte is studied. It is shown that the codeposition of copper and tin is observed only at the potentials, which provide the discharge of copper(II) ions under the diffusion control. The transient time of electroreduction of copper(II) ions and the concentrations of Cu2+ ions in the near-cathode region in the pause are calculated. It is shown that a decrease of the pause duration leads to the alloy deposition at lower current densities. It is found that the use of pulsed electrolysis enables one to raise significantly (by 3 times) the range of cathodic current densities for production of high-quality yellow-bronze coatings. The effect of pulse duration and amplitude on the qualitative and quantitative compositions of the alloy is determined.

Synthesis of mono- and bis-spirooxindole derivatives "on water" using double salt of aluminum sulfate-sulfuric acid as a reusable catalyst.

The preparation of double salt of aluminum sulfate-sulfuric acid (Al4(SO4)6·(H2SO4)·24H2O) by the reaction of aluminum sulfate and sulfuric acid in water is described. Aluminum sulfate-sulfuric acid is characterized via some spectroscopic and microscopic techniques such as infrared spectroscopy (IR), X-ray diffraction spectroscopy (XRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which corroborated the structure of the double salt. This double salt is soluble in water and insoluble in organic solvents. It was employed as a new catalyst for the synthesis of spirooxindole compounds on water with good to excellent yields. The double salt could be recycled and reused without appreciable loss of activity.

A process combination of ion exchange and electrodialysis for the recovery and purification of hydroxy acids from secondary sources

Ion exchange and electrodialysis processes for the production of hydroxy acids (HAs) from alkaline soda and kraft black liquors (BLs) were investigated. Ion exchange with a type-2 strong anion exchange resin in sulfate form was used to separate thiosulfate from alkaline kraft-BL-based mixture of sodium (Na+) salts of HAs. Efficient regeneration of the spent resin to sulfate form was achieved only through hydroxide form. Ion exchange with strong cation exchange (SAC) resins was successfully used to convert the Na+ salts of HAs in soda-BL-based solution and thiosulfate-free kraft-BL-based solution into free acids with complete removal of Na+ ions from the solution. The spent resin was efficiently regenerated with 1–2 mol/L sulfuric acid (H2SO4). Electrodialysis with bipolar membranes (EDBM) was used for the generation of H2SO4 and sodium hydroxide (NaOH) from the spent SAC resin regenerants (sodium sulfate–sulfuric acid mixtures). Overall, 1 mol/L H2SO4 with 95% purity and 90% yield could be obtained, but excess water flux through the membranes limited the maximum obtainable H2SO4 concentration to 1.17 mol/L. Simultaneously, 0.79 mol/L NaOH was produced with 93% purity. EDBM-based H2SO4 was successfully used for the regeneration of the SAC resin. With EDBM, a closed loop can be built for the regeneration of SAC resin with the simultaneous generation of NaOH. The results of this study demonstrate that a process combination of ion exchange and electrodialysis decreases the overall chemical consumption related to HA production and enables efficient chemical recycling.

Diffusion-Reaction-Limited Mass Transfer on the Surface of an Electrically Conductive Droplet

Electrometallurgical processes are widely utilized in extraction and refining of metals [1]. Copper magneto-electrolysis [2] and aluminium smelting [3] are used to extract metals. Electroslag remelting (ESR) process is extensively used to refine metals [4]. A wide range of electrolytes such as copper sulphate-based, CaF2-based, and sodium hexafluoroaluminate are used. Some of those processes (e.g. ESR) involve formation of metallic droplets which travel through the electrolyte. Electrochemical (Faradaic) reactions take place at the droplet-electrolyte interface aiming at refining of the metal. Generally, the electrolyte operates at elevated temperature (~ 2000 K) and high electric current density (~ 105 A.m-2) during refinement of the metal. As such, experimental analysis and measurements are quite difficult. Therefore, simulation tools can be effectively used to get insight into the invisible phenomena. Computational fluid dynamics (CFD) is a powerful technique that enables us to gain a deeper knowledge of the aforementioned processes. The obtained knowledge can be used to improve the technology, to minimize the failure rate, and to increase productivity. Here, we propose a CFD model to study the electrochemical mass transfer at a droplet-electrolyte interface. The transport phenomena including flow, concentration, and electric current density fields are computed. A fully coupled model is developed to determine the concentration of the reactant as well as electric potential at the droplet-electrolyte interface. For that purpose, the interplay between the reaction kinetics at the droplet-electrolyte interface (Butler-volmer formula) and the diffusion-advection of reactant through the hydrodynamic boundary layer around the droplet is taken into account. The condition of the presences of excess of supporting electrolyte is assumed so that the migration transport of the reactant is ignored [5]. Of note, the droplet acts as both cathode and anode. Thus, the cathodic/anodic area on the surface of droplet must be computed that in turn depends on the intensity of the flow and the droplet size (more precisely Reynolds (Re) number). In the present study, the system is composed of a copper droplet and the copper sulfate-sulfuric acid electrolyte for which kinetic and hydrodynamic properties (e.g. exchange current density, viscosity, etc.) are well-known [6]. Demonstratively, an example of calculations (Re = 40) including the velocity (u), the normalized concentration filed of the Cu2+ reactant (C/C∞ ), and the electric current density (j) is shown in Figure 1. In the bulk of electrolyte, the concentration filed (C∞ ), the velocity field (u∞ ), and the electric field (E∞ ) are given. Several droplet sizes (0.5, 2, 4 mm) under different flow regimes (Re = 0.2, 2, 20, 40 and 80) were examined. It is found that the intensity of the flow filed and the direction/strength of electric field in the bulk of electrolyte can significantly impact the amount of electric current (~ mass transfer) which flows through the droplet. Based on the modeling results, the mass transfer is limited mainly by reaction for the small droplet, whereas the role of diffusion becomes more potent with the increase of the droplet size. Figure 1. Field structures are shown for the droplet with 2 mm diameter at Re = 40. In each contour the magnitude (colour scale) and the direction (equisized vectors) is illustrated. (left) velocity field, (middle) concentration field, (right) electric current density field.

Microstructure and Selective Corrosion of Alloy 625 Obtained by Means of Laser Powder Bed Fusion.

The effect of microstructure on the susceptibility to selective corrosion of Alloy 625 produced by laser powder bed fusion (LPBF) process was investigated through intergranular corrosion tests according to ASTM G28 standard. The effect of heat treatment on selective corrosion susceptibility was also evaluated. The behavior was compared to commercial hot-worked, heat treated Grade 1 Alloy 625. The morphology of attack after boiling ferric sulfate-sulfuric acid test according to ASTM G28 standard is less penetrating for LPBF 625 alloy compared to hot-worked and heat-treated alloy both in as-built condition and after heat treatment. The different attack morphology can be ascribed to the oversaturation of the alloying elements in the nickel austenitic matrix obtained due to the very high cooling rate. On as-built specimens, a shallow selective attack of the border of the melt pools was observed, which disappeared after the heat treatment. The results confirmed similar intergranular corrosion susceptibility, but different corrosion morphologies were detected. The results are discussed in relation to the unique microstructures of LPBF manufactured alloys.

Ultrasound augmented leaching of nickel sulfate in sulfuric acid and hydrogen peroxide media

A new method of preparation high purity nickel sulfate assisted by ultrasonic was studied. The process mechanism was analyzed by Inductively Coupled Plasma (ICP), X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Energy dispersive X-ray spectrometry (EDS).The reaction mechanisms of oxidizing leaching and ultrasonic leaching were explored, respectively. Results showed that ultrasonic treatment peel off the oxide film on the surface of nickel. The leachate under strongly agitated, the yield rate of nickel sulfate was accelerate. And the reaction area was increased by the cavitation effect, the liquid-solid reaction was promoted, and the activation energy was reduced. The leaching rate of nickel reached 46.29% by conventional leaching, which takes about 5h. Under the same conditions, the ultrasonic leaching rate reached 40%, only half of the conventional leaching time. Concentration of leaching agent, reaction temperature, ultrasonic power, leaching time had significant effect on the enhancement of the leaching reaction with ultrasonic radiation. The leaching rate of 60.41% under the optimum experiment conditions as follows: sulfuric acid concentration 30%, hydrogen peroxide 10%, leaching temperature 333K, ultrasonic power 200W and leaching time 4h. The kinetic study of the system was investigated, and the reaction rates of conventional leaching and ultrasonic leaching were controlled by diffusion, and the apparent activation energies were 16.2kJ/mol and 11.83kJ/mol.

Phase and extraction equilibria in H2O–sulfonol–HCl (H2SO4) and H2O–sodium dodecyl sulfate–HCl (H2SO4) systems

Solubility isotherms of water–sulfonol–hydrochloric (or sulfuric) acid and water–sodium dodecyl sulfate–hydrochloric acid systems at 75°C and a water–sodium dodecyl sulfate–sulfuric acid system at 50°C are constructed. Regions of two-phase liquid equilibrium suitable for use in extraction are found. Concentration parameters for extraction are determined. The interfacial distribution of a series of metal ions with and without such additional complexing reagents as diantipyrylmethane and diantipyrylheptane is studied.

Effect of pressure on the stability and ability to drying of water-saturated gases

The inorganic salts-based solid phase adsorbents are often used as driers of gases or weakly polar liquids (for example – ethanol) as the cations of metal elements have the ability to readily form aquacomplex compounds, which easily solidify and form crystalline hydrates. However, since there is often a need to conduct drying gas from other pressure than atmospheric pressure, there is a need to carry out the dependence of properties of inorganic salts, which form crystalline hydrates, from the pressure. Results based on the use of four different inorganic adsorbents have shown that the pressure increase accelerates dehydration and generally deepens its extent. It is caused both by van der Waals bonds and a more effective mechanism for the formation of bonds of the donor-acceptor mechanism. Effect of pressure increase on various adsorbents is uneven and is linked to the strength of relationships, which are formed by a cationic mechanism, and is also associated with coordination number of the central atom, its radius, the distance to its electron shells and the position in the periodic table. The results make it possible to develop an adsorbent for effective drying gas to replace traditional gas drier, such as phosphorus (V) oxide, and sulfate (sulfuric) acid.

Synthesis of semiconductor oxide nanosheets, nanotetrapods and nanoplane-suite like grown on metal foil using different method

ZnO production nanostructure using different method: first method, electrochemical deposition on Zn foil using 0.3 M zinc sulfate heptahydrate (ZnSO4·7H2O) and sulfuric acid aqueous solution at a current density of 30 and 35 mA/cm2 for deposition time 40 min at room temperature and second method, Zn foils were thermally oxidized in a conventional tube furnace at a temperature equal range of 700–900 °C in air for 5 h or less in static air to prepared semiconductor nanomaterials ZnO nanorods, nanotetrapods and nanoplane. The XRD diffraction of higher intensity peaks at (101) and (002) miller indices for two methods can be recognized to a hexagonal wurtzite structure unit cell. Surface morphology images with different magnifications which clearly shows that the whole Zn foil and rod substrate obtained ZnO nanosheets, nanotetrapods, nanorods and growth nanoplanes were also found. The length of these nanotetrapods and nanorods lies in the equal range of 1–1.5 µm with an average diameter of 80 nm. It was well known that ZnO nano crystal exhibited two emission peaks. One was located at about 365 nm wavelength (UV luminescence band), and the other peak position at 475 nm wavelength (green luminescence band).

Electroforming of oxide-nanoparticle-reinforced copper-matrix composite

Abstract

Numerical Simulation of a Batch Rotating Cylinder Electrode System for Bulk Electrolysis

The numerical simulation of a batch rotating cylinder electrode (RCE) system for bulk electrolysis was investigated. This study focused on the transient tertiary current distribution and cell configurations for electrolysis of copper sulfate in sulfuric acid. The simulated flow field of an RCE shows one vortex around the axisymmetric cutting plane of the cell when the distance from RCE to container bottom is no more than 5 cm, or double-vortex flow pattern appears. The flow field influences the mass transport of copper ions and then causes the accumulation at the top corner of the cell, proved by the simulated concentration profile. The transient simulation exhibits two-stage development of the concentration distribution between the RCE and anode. In the first stage, the diffusion layer extends with time while the bulk region becomes indefinite in the second stage. Furthermore, hydrogen reduction affects the current density on the RCE, resulting in a decreasing current efficiency with passing time. Although the simulated residual fractions of copper ions slightly deviate from the conventional macroscopic prediction due to the cell configuration and side reaction, the simulated results are consistent with those from the experiments and can provide the information of cell design on the bulk electrolysis.

Hydrochemistry and isotopic characteristics of non-volcanic hot springs around the Miocene Kofu granitic complex surrounding the Kofu Basin in the South Fossa Magna region, central Honshu, Japan

‐4.6‰, whereas waters from the magnetite series area have positive δ 34 S values ranging from +1.7 to +8.0‰. The hot spring water quality of the Na‐Alk, Na‐SO 4 , Na‐SO 4 ·Cl·Alk, and Ca‐SO 4 types from the volcanic rocks area were estimated to be controlled by anhydrite dissolution, plagioclase weathering, cation exchange reaction of Na‐ montmorillonite, and precipitation of calcite during the fluid flow and mixing process. Different concentrations of SO 4 2‐ ions determined for these waters have a wide range of δ 34 S values ranging from ‐4.1 to +13.6‰, which is likely attributed to the dissolution of 34 S-rich and 34 S-poor anhydrite. The 34 S-rich SO4 2‐ ions were interpreted to be derived from sulfate in sulfuric acid, which arose from the disproportionation reaction of volcanic sulfur dioxide, whereas the 34 S-poor SO 4 2‐ ions were derived from the oxidation of ascending hydrogen sulfide in shallow ground waters during the active stage of past volcanism.

AFM Studies of the Effect of Chloride Ion on the Morphology of the Copper Electroplating Surface

The influence of plating mode, chloride ion on morphology of copper deposits has been studied on pure copper substrate. The electroplating was conducted at 50mA/〖cm〗^2 , 25°C in cupric sulfate-sulfuric acid bath with various chloride additions 0.001-0.01 ml. The morphology and grain sizes of the electrodeposited copper were examined by atomic force microscopy. The maximum surface roughness and grain sizes of copper deposit were obtained when it was deposited with 0.01 ml of chloride ions. Small particles were observed on the surface of the copper film electroplated with the addition of chloride ions up to the amount of 0.001 ml.

Kinetics study of selenium removal from copper sulfate–sulfuric acid solution

The chemistry and kinetics of the removal of selenium from copper sulfate–sulfuric acid solution by cuprous ion reduction and precipitation were studied. Continuous measurement of [Cu+] was carried out by potentiometric monitoring. The stoichiometry of the overall reaction was found to be: HSeO4−+9.96 Cu+ aq+7H+=Cu1.98Se+4H2O+7.98Cu+2 at 95.1°C. The reaction mechanism appears to be based on an initial one electron transfer to form intermediate Se(V). The kinetics fit the rate law: −dSeVIdt=k1Cu+2SeVIk−1k2Cu+2+Cu+ at constant acidity. The values of k1 and k−1/k2 were 0.0055M−1s−1 and 1.5×10−4 at [H2SO4]=100g/L, [Cu+2]=50g/L at 95.1°C. Rate constants are almost independent of cupric concentration at constant ionic strength but decrease slightly with increasing cupric concentration and increasing ionic strength. Activation energy of 85.5kJ/mol for k1 was calculated by varying the temperature from 86.1 to 98.6°C. Cuprous selenide precipitates react with cupric ion and generate cuprous ion and non-stoichiometric CuxSe precipitate (1.88<x<1.94). Increasing solution acidity significantly increases the biselenate reduction reaction rate. An empirical correlation of k1=0.0058 [H2SO4]1.25 was found between the sulfuric acid concentrations in the range of 10 to 200g/L and k1. The biselenate reduction reaction was also investigated in the non-complexing perchlorate medium to study the effects of acidity and ionic strength without the complication of weak dissociation of HSO4− and ion pairing effects. Cuprous is oxidized slowly by perchlorate species. The rate of cuprous oxidation was first order with respect to cuprous concentration ([Cu+]=[Cu+0]×e−kt). This rate equation was used to modify the rate of biselenate reduction reaction in perchlorate medium. An empirical correlation of k1=0.0159 [H+] 0.9 was found between the H+ concentrations in the range of 10 to 150g/L HClO4 and I=4.35m at 95.1°C. Biselenate removal rate increases significantly by increasing the ionic strength of the solution. k1 values vary from 0.0075 to 0.0412M−1s−1 in solutions containing 0 to 3M NaClO4 at 95.1°C and [HClO4]=100g/L, [Cu(ClO4)2]=50g/L. Linear correlation between log k1 and solution nominal ionic strength was obtained as log k1=−9.135+10.800×[I1/2/(1+I1/2)] in perchlorate medium at 95.1°C. Despite the results achieved in the perchlorate medium, biselenate removal rate decreases in sulfate bearing solutions by addition of sulfate based salts. This almost certainly has to do with decreasing free acid levels due to formation of bisulfate anion.

Feasibility study of hydrogen/iron redox flow cell for grid-storage applications

In this study, the hydrogen/iron redox flow cell was evaluated in order to estimate its potential as an energy-storage system. The system was studied for the first time, for energy-storage applications, with electrolytes composed of several different iron salts and their conjugate acids. Cell performance varied with electrolyte composition. Best results were obtained with a solution of iron sulfate in sulfuric acid: stable performance, good capacity utilization, energy-conversion efficiency of up to 82% and a power density of up to 0.27Wcm−2, with no optimization of cell components. The results show the potential of the hydrogen/iron system as a candidate for energy-storage and further optimization should greatly enhance performance.

Equilibrium cuprous concentrations in copper sulfate–sulfuric acid solutions containing 50–110 g/L Cu+ 2 and 10–200 g/L H2SO4 at 50–95 °C

Copper sulfate (66–323g/kg H2O; ~25–110g/L Cu+2) and sulfuric acid (10–233g/kg H2O, ~10–200g/L) solutions were reacted with copper metal at temperatures between 50 and 95°C to form Cu+ until equilibrium was attained. Samples were collected into an NH4Fe(SO4)2·12H2O solution to convert cuprous to ferrous, which were then titrated with standard Ce(IV) using very dilute ferroin as the indicator. In order to estimate solution compositions in volumetric units (e.g. g/L) the densities of the parent CuSO4–H2SO4 solutions at the reaction temperatures were used. Some additional density data, beyond that available in the literature was needed. Density as a function of temperature and masses of CuSO4 and H2SO4 per kg of water was fitted to an empirical equation. Density was also estimated based on known concentrations of Cu+2 and H2SO4 in g/L and temperature using an alternative correlation. Cuprous concentrations were determined as mol/kg of sample. Cuprous concentrations in g/L were fitted to an expression of the form:Cu+=Ve−W/TCu+2XYH2SO42+ZH2SO4+1where [Cu+], [Cu+2] and [H2SO4] are in g/L at specified temperature T (K) and V–Z are empirical constants. The empirical expression simulated the measured [Cu+] to within ±3.6%. The cuprous concentrations were also fitted to the same type of equation using concentrations on the molal scale. These matched the experimental values to within ±3.5%. Varying sulfuric acid concentrations were found to have only a modest influence on the equilibrium cuprous concentrations. With 10–200g/L H2SO4 and a given [Cu+2] the difference between the highest and lowest [Cu+] was 7% at most. At 95°C with a solution containing 107–109g/L Cu+2 and 10–200g/L H2SO4, the [Cu+] was 1.70–1.75g/L.