Dilute Chloride Solutions Research Articles

Ion-exchange separation and spectrophotometric determination of traces of gold.

A combined ion-exchange — spectrophotometric method has been developed for the separation and determination of traces of Au(III) in seven metal ions: Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Se(IV) and Cd(II). Au(III) is adsorbed selectively on a DEAE column from dilute chloride solution, while other metal ions pass through the column. Au(III) is recovered by elution with 1M hydrochloric acid. Traces of Au(III) in the effluent are determined by a new spectrophotometric method, which is based on the formation and extraction of Au(III) — azide — methylene blue complex. Separations of traces of Au(III) from 1000-fold of Pd(II) and Pt(IV) and 10000-fold of Hg(II) are also effected on a DEAE column in mixed methanol 1M hydrochloric acid medium (8 ∶ 2). While Pd(II), Pt(IV) and Hg(II) are retained on the column, Au(III) adsorbs very weakly, so that the separations can be accomplished easily.

Elimination of the diffuse layer by specific adsorption of anions on mercury from dilute aqueous solutions

The electronic surface charge density of mercury electrodes has been measured as a function of their potentials in solutions of 1 mM MX, 1 mM MX+50 μM Na2SO4, and 1 mM MX+50 μM LaCl3, where MX is NaF, NaN3, NaCl, KNO3, KI, and NaH2PO4. In the cases of NaN3, NaCl, and KNO3, plots of the surface charge density vs. potential on the positive side of the potential of zero charge are essentially identical whether or not the multiply-charged ions are present. This indicates that there is no diffuse layer present, that the potential at the outer Helmholtz layer is zero, and that the amount of anion specifically adsorbed is equal in magnitude to the surface charge density, in accord with previous conclusions based on differential capacity measurements. In the case of 1 mM KI, the anion adsorption slightly exceeds the surface charge density at all positive values of the electronic surface charge density but may match it at lower concentrations. As fluoride is added to dilute chloride solutions no diffuse layer appears until fluoride concentrations in excess of 10 mM are reached. The observed behavior is qualitatively explained on the basis of ideas previously discussed by others5,15.

Elimination of the diffuse layer by specific adsorption of anions on mercury from dilute aqueous solutions

Summary The electronic surface charge density of mercury electrodes has been measured as a function of their potentials in solutions of 1 mM MX, 1 mM MX+50 μM Na2SO4, and 1 mM MX+50 μM LaCl3, where MX is NaF, NaN3, NaCl, KNO3, KI, and NaH2PO4. In the cases of NaN3, NaCl, and KNO3, plots of the surface charge density vs. potential on the positive side of the potential of zero charge are essentially identical whether or not the multiply-charged ions are present. This indicates that there is no diffuse layer present, that the potential at the outer Helmholtz layer is zero, and that the amount of anion specifically adsorbed is equal in magnitude to the surface charge density, in accord with previous conclusions based on differential capacity measurements. In the case of 1 mM KI, the anion adsorption slightly exceeds the surface charge density at all positive values of the electronic surface charge density but may match it at lower concentrations. As fluoride is added to dilute chloride solutions no diffuse layer appears until fluoride concentrations in excess of 10 mM are reached. The observed behavior is qualitatively explained on the basis of ideas previously discussed by others5,15.

Enthalpy of formation of europium dichloride and thermodynamic properties of the +2 and +3 aqueous ions of europium

Enthalpies of solution of anhydrous EuCl2 have been measured at 298.15 K in dilute hydrochloric acid solutions which were either oxygen-saturated or oxygen-free. Because of ambiguity in the oxidation of Eu2+(aq) by oxygen, enthalpies of oxidation of Eu2+(aq) have also been measured using bromine water and liquid bromine. Combined with other recent thermochemical measurements, the above experiments yield ΔHof(Eu2+, aq) = −(527.8 ± 5.4) kJ mol−1, ΔHof(Eu3+, aq) = −(604.8 ± 3.8) kJ mol−1, and ΔHof(EuCl2, c) = −(824.4 ± 5.9) kJ mol−1. The Eu(III, II) electrode potential has been measured in dilute chloride solutions, with the recommended result −(0.35 ± 0.03) V. These data have been combined to yield So(Eu2+, aq) = −(10 ± 12) J K−1 mol−1.

Studies on the Production and Utilization of Regenerated Humic Acids

The regenerated hurnic acids (powder) prepared by oxidation of 6 Japanese bituminous coals (C: 75.7-89.5%) have studied on their ion exchange properties in heavy metal ion solutions. The adsorption ability of humic acids on Cd ion in its dilute chloride solution (1/5000M) increased in following order: natural humic acids extracted from lignites <those prepared by the oxidation with air <those by the oxidation with nitric acid (nitrohurnic acids), though the content of carboxyl group in humic acid increased in following order: those by the oxidation with nitric acid<natural hurnic acids <those by the oxidation with air. Nitrohumic acid was characteristic of its high ion exchange velocity comparable with that of Amberlite CG-120 and its high ion exchange velocity comparable with that of Amberlite CG-120 and its high adsorption ability on Zn, Cd and Cu ions from their dilute solutions at pH≥3.5. The adsorption of Cd ion was more effective on the nitrohumic acid of partial sodium salts type, on which saturation adsorption in Cd-, Zn-, Ca- and Mg-chloride solutions at initial pH 5 was ca. 1.0, 0.9, 0.6 and 0.5meq./g, respectively. The regeneration of nitrohumic acid having adsorbed Cd ion could be effectively done with 1M NaCl solution or 1M NaCl solution in two steps, and the adsorption ability after repeating regeneration of 6 times did not decrease. When the regeneration has been done with varying amounts of hydrochloric acid (0.5 N initial concentration), Cd ion concentration in equilibrated solutions at 99-100% and 90-92% regeneration ratio of humic acid was ca. 10-2M and 1M, respectively.

耐候鋼のさび層に関する研究

The amount of sulfate absorbed by “artificial rust” and by natural rust separated from iron-copper alloys which had been exposed for one year has been determined in sodium sulfate and ferric sulfate solutions. The apparent permeation rate of sodium sulfate through pores of the artificial rust and the membrane potential difference across the rust layer in chloride solutions have also been determined. Calculation based on the amount of sulfate absorbed and the calculated pore volume of the rust shows that the sulfate within rust pores is highly concentrated. The ratio of the concentration of sodium sulfate in rust pores to that bulk solution in which the rust specimen is immersed is about 80 for the artificial rust consisting of crystalline magnetite while the ratio is about 250 for the amorphous artificial rust containing 5.1% copper. The presence of copper in rust retards permeation of sulfate through the rust. The determination of the membrane potential indicates that rust acts as an anion exchange membrane in dilute chloride solutions. The behavior of electrolyte in rust depends not only on the physical structure of the rust but also on its colloid-chemical characteristics.

An Assembly for Electrochemical Corrosion Studies in Aqueous Environments at High Temperature and Pressure

Abstract An assembly is described, in which electrochemical corrosion measurements can be carried out in aqueous environments up to 314 C (598 F) and 105.5 kg/cm2. Test specimen mounting and corrosive environment containment procedures are discussed. A techniqie for using a high pressure electrolyte bridge with an external reference electrode is described. The performance of the system is demonstrated by potentiostatic anodic, cathodic and linear polarization experiments carried out on AISI Type 304 steel in dilute chloride solutions at 289 C.

Seasonal changes in the amounts of phosphorus and potassium dissolved from soils by dilute calcium chloride solutions

Variations during 12 months in the concentrations of soil P and K soluble in 0-01M CaCl2 solution were measured on several sites with contrasted histories at both Rothamsted and Woburn. Concentrations were always less in fresh than in airdried soils.P concentrations in the heavy soils at Rothamsted were remarkably constant, seasonal variation only occurring where FYM or phosphate fertilizers had been applied during the year. At Woburn P concentrations were also constant in the poorer soils, but varied during the year in rich soils.On Barnfield at Rothamsted the plots receiving FYM each year contained more soluble P than those treated with superphosphate. Where both FYM and superphosphate were applied, P concentrations were greater than the sum of values on plots receiving FYM and superphosphate separately because a given amount of P remained more soluble when FYM was regularly applied. P also remained more soluble on plots given ammonium sulphate.

NaCl水溶液中におけるCuの陽極的挙動

The anodic behavior of copper in air-saturated NaCl aqueous solutions has been studied by both galvanostatic and potentiodynamic methods to determine the effects of the Cl− ion concentration and temperature on the dissolution of copper. The polarization curves of copper represents the two active-passive transitions. In a less noble electrode potential region, a CuCl layer was formed on copper. It was then transformed into Cu2O by the reaction with H2O and the first passivation occurred. The potential of the CuCl formation in the strong chloride solution was less noble than that in the dilute chloride solution. In an intermediate potential region, the second passivation begins when the reaction is proceeded between Cl− ion and CuCl to form Cu2O. Although CuCl is not direct cause of the passivation of copper, a stable region of Cu2O extends due to decreasing Cl− ion concentration in the electrode-solution interface by the formation of CuCl. To help interpretation of the polarization curves, a potential-pH diagram of the Cu-Cl-H2O system has shown the domains of the stable solid phase in 0.3 to 30%NaCl aqueous solutions.

Initial Stages Of Stress Corrosion Cracking In Austenitic Stainless Steels

Abstract Initial stages of stress corrosion cracking in Types 304 and 304L stainless steel were investigated with optical and electron microscopy techniques. Studies of U-bend samples and electron-transmission quality thin foils revealed that cracks initiated preferentially on the {111} family of planes and that formation of corrosion products accompanied both crack nucleation and propagation. U-bend samples formed from metal-lographically polished strips were studied after exposures in 42 percent MgCl2 solutions at 154 C (309.2 F). Tiny corrosion pits were observed initially, then extension of corrosion formed linear traces of corrosion product on the sample surfaces. These traces lay parallel to the {ill} traces on grain surfaces and cracking was seen later in the corroded regions. Samples then had many small cracks which often formed Widmanstatten-like patterns in several grains. All the small cracks were in corroded regions and were on the {111} family of planes. Continued exposure caused the small cracks to propagate, interconnect and form characteristic trans-granular branching crack patterns. Electron transmission studies of thin foils exposed to dilute chloride solutions revealed a similar sequence of crack initiation and propagation. Preferential pitting formed linear arrays along {111} traces on the foil surfaces. Also, preferential attack occurred at stacking faults and dislocation arrays, producing crack-like voids in the foil. Extent of preferential attack increased with increasing exposure time and temperature and corrosion products were observed in regions of attack. Foils exposed under similar conditions to deionized water and solutions of NaI did not contain the attacked regions, demonstrating importance of chloride ion in the stress corrosion process. These results support the electrochemical mechanism of crack propagation by localized anodic dissolution and show that crystallographic defects provide the sites for such attack.

塩化物水溶液によるオーステナイトステンレス鋼の応力腐食割れについて

An investigation was carried out on the effect of stress, chloride concentration, temperature and oxygen on the stress corrosion cracking behaviour of 18-8 and 18-13 Mo steels. Tests were made in autoclaves with the chloride ion concentration of 0∼300,000 ppm at 130°∼250°C. The susceptibility for stress corrosion cracking was found to increase with the increase of chloride concentration and/or temperature. At temperatures blow 150°C, no stress corrosion cracking was observed except in boiling 42%MgCl2 solution. Above 180°C, susceptibility was much greater in vapor phase than in liquid phase. In the atmosphere of air 18-8 steel cracked at 180°C with 30,000 ppm chloride concentration in liquid phase and 30 ppm in vapor phase, wherease at 250°C it cracked with 10 ppm chloride concentration in vapor phase. Addition of oxygen in autoclaves promoted the tendency to stress corrosion cracking; at 180°C 18-8 steel cracked with 300 ppm chloride ion concentration in liquid phase and 10 ppm in vapor phase.The 18-13 Mo steel was observed to be more susceptible than 18-8 steel in vapor phase and less susceptible in liquid phase in dilute chloride solution, whereas in boiling 42%MgCl2 solution both steels were almost equally susceptible. These results suggested the pressence of definite threshold stresses for stress corrosion cracking which depended on chemical composition and corrosive environments such as temperature, chloride and oxygen concentrations. It was also observed that in dilute chloride solutions all cracks were originated at pits formed in both vapor and liquid phase and that complete exclusion of oxygen eliminated the occurrence of stress corrosion cracking as well as pitting corrosion.

Solubility of simple aluminium compounds expected in soils. II. Hydrolysis and conductance of Al3+

The results of conductimetric measurements on dilute aluminium chloride solutions at 25� were found to be best fitted by the limiting equivalent conductances A01/3Al3 + = A01/2AlOH2+ = 58.2 with the parameter for ionic diameter 6.0A and by *K1 = log [(AlOH2+)(H+)/(Al3+)] = - 5.05 when it was assumed that AlOH2+ and H+ concentrations produced by hydrolysis were equal in the measured solutions. Potentiometric measurements and calculations from solubility work gave *K1 = -5.00 and -4.97 respectively. After small changes, e.g. by aging, dilute aluminium salt solutions conform to the solubility expression for aluminium hydroxide, log [(AlOH2+) (OH-)2] = -23.31.

The corrosion of tin and tinned copper in dilute neutral solutions

AbstractLocal corrosion of tin by dilute chloride solutions is not prevented indefinitely by special physical or chemical preparation of the metal surface, or by alloying additions to the metal. The time elapsing before local corrosion begins is affected by surface condition and, with increase in the severity of attack, by contact of the metal with another solid surface to form a crevice, reduction of pH of the solution and electrical contact with a more noble metal.The intermetallic compounds formed in hot‐dipped or wiped coatings of tin on copper are resistant to corrosion and may be slightly cathodic to copper, but tin remained anodic to copper even when ennobled by oxide films. Wiped coatings on copper are more susceptible to local corrosion than electrodeposited or hot‐dipped coatings because the attack on the free tin remaining on the surface is stimulated by contact with exposed areas of tin–copper compound.Addition of sodium bicarbonate, carbonate, benzoate, chromate, phosphate or silicate to chloride solutions prevents local corrosion and cathodic protection can be obtained with aluminium anodes.

The Ionic Conductivity of Dilute Potassium Chloride Solutions at Centimetric Wavelengths

A differential method is described for measuring the ionic conductivity of potassium chloride solutions at 3 × 109 c/s. The results reveal that a strong dispersion region exists at concentrations below 0.5 normal, which may be explained in terms of the perturbations by the applied field of a shell of water molecules surrounding the ion at a mean distance of 6 A.

The relative proportions of exchangeable bases in some Scottish soils

1. The relative proportions of exchangeable bases in nine soils from the east of Scotland area and the changes effected by dilute chloride solutions have been examined.2. The changes due to N/50 solutions are large, and magnesium is displaced to a greater extent by calcium than by potassium.3. The changes due to N/500 solutions are very small, comparable to what might be expected in manurial practice, and not greater than field sampling error.4. The content of exchangeable bases and their relative proportions, therefore, seem to be fairly permanent for any soil under normal conditions, but vary considerably from soil to soil, and should prove useful as an additional characteristic of soil type as distinguished in the field.