Copper-Phosphoric Acid Solution

Experimental study indicated that the mass transport limiting species in copper-phosphoric acid solution is the so-called acceptor (water molecules), which diffuses into the diffusion layer and facilitates Cu removal [14]. In some cases, a salt film of metal ion complexes can form as an anodic layer to control the mass transport processes [15-17]. Mass transport limiting species can also be metal ions, which diffuse and migrate through anodic layers (ionconcentrated diffusion layer and/or salt film) into the bulk solution [17]. 

Depending on the anode material, electrolyte, and other factors, the polarization curves can have various shapes. A typical polarization curve of copper in phosphoric acid solution is shown in Fig. 10.6. At low potential (close to zero), electrochemical reactions of low redox potentials such as... 

Thermal ionization has been used to determine isotopic abundance of virtually all the elements We have recently extnded our own capability in this direction by adapting the silica gel/phosphoric acid filament coating technique (5) to our system Five 1 of a fine silica gel suspension is placed on a filament Five l of the analyte ion solution is coated, dried then coated with 2 pi of a 0 7N phosphoric acid solution and heated until dry again The analysis is performed in a similar manner as before, except that the signal is more transient and somewhat less intense than the calcium analysis With this approach, however, we have made natural abundance isotope ratio measurements on zinc, copper, and magnesium Table II shows our measurements compared to the accepted values, shown in parenthesis, for these elements The isotope used as reference... 

Internal (carrier) driving force coefficients, and K, <, or distribution coefficients, Ep and E, are determined by membrane-based extraction experiments. Membrane-based forward and backward extraction is carried out in two-compartment modules using the F and R compartments, separated by the same membranes as in the BAHLM tests. The experiments lasted up to equilibrium conditions, when the concentration of solutes in every compartment does not change with time. Examples of membrane-based extraction of copper, cadmium, and zinc from the concentrated phosphoric acid solution by PVSH and backward extraction by 2 M HCl are presented in Table 6.2 [7]. 

To prepare it, protochlftride of mercury (calomel) is rapidly mixed with aqua potasses in excess, by rubbing in a mortar and the black powder formed is washed with cold water and dried in the dark. HgCl + KO = KCl + HgO. It is a black or dark olive powder, which is easily resolved into peroxide and metal 2 HgO = HgO + Hg and hence is difficult,to keep. It is a feeble base, and forms with acids ciystaUisable salts, such as the acetate and nitrate. Its solutions are precipitated black by caustic alkalies white (calomel) by hydrochloric acid, or a soluble chloride and the metal is reduced by copper, phosphorous acid, or protochloride of tin. 

Edwards J (1953) The mechanism of electropohshing of copper in phosphoric acid solutions. I. Processes preceding the establishment of polishing conditions. J Electrochem Soc... 

The higher nickel content of alloy 825 compared to alloy 800 makes it resistant to chloride SCC. Addition of molybdenum and copper gives resistance to pitting and to corrosion in reducing acid environments, such as sulfuric and phosphoric acid solutions. Alloy 825 is resistant to pure sulfuric acid solutions up to 40% by weight at boiling temperatures and at all concentrations at a maximum temperature of 150°F (60°C). In dilute solutions, the presence of oxidizing salts such as cupric or ferric actually reduces the corrosion rates. It has limited use in hydrochloric or hydrofluoric acids. 

Twenty per cent TBF dissolved In kerosene was used as extractant. The partition coefficient, increases with Increased TBF concentration. Increases with increased pH, and decreases with increased sulfate concentration. Vanadium and Iron (ill) are appreciably extracted by TBP from thiocyanate solutions. Copper, titanium, cobalt are weakly extracted. Iron (ll), cadmium, molybdenum, magnesium and aluminum are essentially not extracted. Phosphate Ion may cause the precipitation of uranium or complex formation when present in large amounts. Okada, et al. report the extraction of uranium by TBP, mesityl oxide, and methyl ethyl ketone from phosphoric acid solutions having 20 times as much ammonium thiocyanate as uranium. 

Dipping solution Dissolve 3g copper(II) acetate in 100 ml 8-15% aqueous phosphoric acid. 

Zinc-Copper Couple A 500-ml Erlenmeyer flask equipped for magnetic stirring is charged with a mixture of zinc powder (49.2 g, 0.75 g-atom) and hydrochloric acid (40 ml of 3 % aqueous solution). The contents of the flask are rapidly stirred for 1 minute, and the liquid is decanted. Similarly, the zinc is washed with the following three times with 40 ml of 3% hydrochloric acid solution, five times with 100 ml of distilled water, five times with 75 ml of 2 % aqueous copper sulfate solution, five times with 100 ml of distilled water, four times with 100 ml of absolute ethanol, and five times with 100 ml of absolute ether. These last ethanol and ether washes are decanted onto a Buchner funnel to prevent loss. The residue is collected by suction filtration, washed again with anhydrous ether, and dried in air. Finally, the zinc-copper couple is stored (20-24 hours) in a vacuum desiccator over phosphorous pentoxide. 

The simplest and most thoroughly studied solutions are those based on phosphoric acid at low temperatures (<35°C) which alone can fulfil all three requirements of acid solvent, film former (as metal phosphate) and diffusion agent by virtue of its viscosity. Thus copper and its main alloys of brasses and bronzes can be very effectively electropolished in 60-70% orthophos-phoric acid with the temperature maintained below 35°C under other conditions copper passivates or dissolves freely under mass transfer controlled conditions, but by varying the conditions appropriately polishing can be continued under mild agitation. An annotated polarisation curve is given in Fig. 11.7 readers are referred to recent studies for more detailed 2ispects " . 

Discussion. Molybdates [Mo(VI)] are quantitatively reduced in 2M hydrochloric acid solution at 60-80 °C by the silver reductor to Mo(V). The reduced molybdenum solution is sufficiently stable over short periods of time in air to be titrated with standard cerium(IV) sulphate solution using ferroin or /V-phenylanthranilic acid as indicator. Nitric acid must be completely absent the presence of a little phosphoric(V) acid during the reduction of the molybdenum(VI) is not harmful and, indeed, appears to increase the rapidity of the subsequent oxidation with cerium(IV) sulphate. Elements such as iron, copper, and vanadium interfere nitrate interferes, since its reduction is catalysed by the presence of molybdates. 

Arsenic(III) sulphide, As2S3 Discussion. The arsenic must be present as arsenic(III), In this condition [ensured by the addition of, for example, iron(II) sulphate, copper(I) chloride, pyrogallol, or phosphorous(III) acid] arsenic may be separated from other elements by distillation from a hydrochloric acid solution, the temperature of the vapour being held below 108 °C arsenic trichloride (also germanium chloride, if present) volatilises and is collected in water or in hydrochloric acid. 

Aqueous solutions of the salts, or of tellurium dioxide in acids, easily undergo reduction.to elementary tellurium. Phosphorus, phosphorous acid,-7 hypophosphorous acid,8 sulphurous acid,9 thiosulphuric acid,10 hyposulphurous acid,11 hydriodic acid,12 hydrogen sulphide,13 ferrous salts, stannous salts,14 hydrazine 15 and phenylhydrazine, as well as various metals,18 e.g. zinc, iron, tin, cadmium, antimony and copper, are able to effect this reduction. 

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