Copper ammonia

A high percentage of the ammonia can be recovered from the spin-bath effluent and by washing prior to the final acid bath. During acidification, remaining ammonia is converted to the sulfate and recovered when the acid wash Hquor is treated with carbonate to recover the copper. Ammonia residuals in the large volumes of washwater can only be removed by distillation. Overall about 75—80% of the ammonia requited to dissolve the cellulose can be recovered. 

The periodic development and use of new steel alloys can improve ferrous corrosion resistance however, where economizer units are constructed of copper alloys, under certain conditions serious copper corrosion problems may result. This occurs when FW having a pH over 8.3 also contains small amounts of ammonia and dissolved oxygen (DO). The ammonia may be present, for example, as a result of the overuse or inappropriate application of certain amines. Further damage may occur from the plating-out of the copper-ammonia ion then created as a cathode on boiler tubes. This promotes anodic corrosion of the immediate surrounding anodic areas. 

The soluble copper ammonia ion passes through the condensate system and plates out as a cathode on steel surfaces in the deaerator, heaters, economizer, and the boiler itself. A secondary galvanic corrosion process is initiated that damages the surrounding steel by forming ferrous hydroxide and releasing copper and ammonia. The ammonia carries over into the steam, and the entire corrosion process repeats itself. 

Animation Figure 15.4 Formation of a copper-ammonia complex... 

MNH3 is added with Cu2+(a ) + 4NH3(a ) Y [Cu(NH3)4]2+(t/<7) What happens depends on the relative values of Kc for the formation of Cu(OH)2(.v) and the Kc for the formation of [Cu(NH3)4]2+Uw/). If one value of Kc is much larger than the other, then that equilibrium will prevail. Since in this problem, we don t know what the Kc values are, we can simply guess that the formation of the copper-ammonia complex would decrease the concentration of Cu2+ in solution and that some or all of the Cu(OH)2(s) might dissolve. 

Thinking Critically In step 2, a deep blue copper-ammonia complex is formed according to the following reaction. 

When large amounts of copper deposits in boiler mbes cannot be removed with hydrochloric acid due to the relative insolubility of copper, ammonia-based oxidizing compounds have been effective. Used in a single separate stage, the ammonia sodium bromate step includes the introduction into the boiler system of solutions containing ammonium bromate to rapidly oxidize and dissolve the copper. 

Most linear ceilulosics may be dissolved in solvents capable of breaking the strong hydrogen bonds. These solvents include aqueous solutions of inorganic acids, zinc chloride, lithium chloride, dimethyl dibenzyl ammonium hydroxide, and cadmium or copper ammonia hydroxide (Schweizer s reagent). Cellulose is also soluble in hydrazine, dimethyl sulfoxide in the presence of formaldehyde, and dimethylformamide in the presence of lithium chloride. The product precipitated by the addition of nonsolvents to these solutions is highly amorphous and is called regenerated cellulose. 

Classroom demonstration of complex equilibria A. R. Johnson, T. M. McQueen, and K. T. Rodolfa, Species Distribution Diagrams in the Copper-Ammonia System, J. Chem. Ed. 2005, 82,408. 

The homogeneity and uniformity of the hydrophobic film formed on the surface of the fibres has been supported by an electron microscope study of the replicas of the surface of the waterproofed cotton fibres. The same result has been given by the study of the film on polyester fibres. Cellulose fibre, treated with waterproofing GKZh-94 catalysed with AHM-9 dissolved in a copper ammonia solution leaves a film which repeats the form of the fibre. 

A change in the color indicates the copper-ammonia complex formation. Adding a strong acid, HC1, to this equilibrium causes the ammonia, NH3, to react with the acid ... 

In the first experiment with the copper-ammonia complex, you added ammonia to change the color and, later, equal strength HC1 to change it back to blue. Did you require more, less, or an equal number of drops from each to accomplish the color change On the basis of stoichiometry, what was your expectation ... 

The new product is commonly known as the copper-ammonia complex ion, or more officially, hexamminecopper(II). This equation is somewhat misleading, however, in that it implies the formation of a new complex where none existed before. In fact, since about 1895 it has been known that the ions of most transition metals dissolve in water to form complexes with water itself, so a better representation of the reaction of dissolved copper with ammonia would be... 

The complexes of amino acids with copper are formed according to the general reaction shown in Equation 7.14 [47]. The formation constants for the copper-amino acid complexes are generally greater than that for copper ammonia complex [48]. Therefore, it is anticipated that amino acids should be more effective than ammonia in assisting the dissolution of oxidized copper during CMP. 

The d—d spectra of copper(II) compounds have been discussed in several recent review articles. Hush and Hobbs (1968) give a detailed account of single crystal spectra measured up to the end of 1967. Hathaway and Tomlinson (1970) have reviewed copper-ammonia complexes, with much emphasis on their electronic properties. Hathaway and Billing... 

Tomlinson and Hathaway (1968b) have reported the spectra of several diamminecopper(II) complexes, and were able to explain satisfactorily the d—d spectra of those compounds whose structures were known the structures of other compounds were predicted from their spectra. Finally Hathaway and Tomlinson (1970) discuss the electronic properties of copper-ammonia complexes in some detail, and give extensive tabulations of spectroscopic data. 

Physical chemists have long been interested in the equilibria established at surfaces. The simplest situation is when we have a gas, such as ammonia, in contact with a surface, such as one of copper. Ammonia molecules are rather strongly attached to such a surface, which may become completely covered by a unimolecular layer. 

In aminations requiring copper, it appears that copper ammonia cations complex with the chloro compound and that this complex addition compound acts as a cyclic catalyst by reacting with ammonia, —OH ion, and the amine. ... 

Moreover, if the silk-fibroin was dissolved in copper-ammonia solution and reprecipitated, its chiral properties were lost. It seems therefore, that the asymmetric properties depends not only on the asymmetric structures of the fibroin but also on the asymmetric structure of the whole molecule... 

All coppei -nickel catalysts were prepared from the magnetically pure copper which was itself completely inactive in the hydrogenation of benzene under the conditions described below. Cupric hydroxide was precipitated from a nitrate solution by dilute ammonium hydroxide solution so that the supernatant liquid was faintly colored by the copper-ammonia complex. The precipitate was filtered and washed. Nickel nitrate in water solution was now added in the proportion desired, and the mixture was stirred to a paste of even consistency. It was dried at 95°, ignited at 180° for 36 hours, and finally at 400° for 20 hours. The oxide mixture was reduced in purified hydrogen at 150° for 20 hours. Most finished catalysts contained 1.0 per cent of nickel. 

It is instructive to compare the copper-ammonia and the copper-ethylenediamine systems. The greater stability of chelates over simple coordination compounds is dramatically seen in the much lower en concentration, 10 M, as compared to 10 M for NHj, at which the free copper ion concentration begins to fall. It will also be observed that the greater separation of the stepwise constants than is observed with simple... 

Haram et al. [385] described a detailed system for the synthesis of CuS nanoparticles using a copper-ammonia complex (pH=l 1) and thiourea in separate microemulsions formed by a non-ionic surfactant (e.g. Triton X-100) with 2-methylpropan-l-ol as co-surfactant and cyclohexane as the oil phase. Other nonionic surfactants used were NP-4, NP-7 and NP-9.5 (nonylphenyl ether surfactant series) the only ionic surfactant used was sodium dodecyl sulfate (SDS). The reactions envisaged were... 

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