Copper oxidations with

With copper alloys containing more noble metals the oxide will be substantially pure copper oxide since the oxides of the noble metals have higher dissociation pressures than the copper oxides. With alloys containing baser metals, however, the alloying element will appear as an oxide in the scale, often in greater concentration than in the alloy itself, and sometimes to the exclusion of copper oxides. The dissociation pressures of many oxides have been calculated by Lustman... 

A.4 Identify all the chemical properties and changes in the following statement Copper is a red-brown element obtained from copper sulfide ores by heating them in air, which forms copper oxide. Heating the copper oxide with carbon produces impure copper, which is purified by electrolysis. ... 

Care must be taken to avoid contamination of the copper oxide with alkaline solutions since such contamination results in nitrogen values which are always too low. The only remedy, should contamination occur, is to boil with acetic acid and re-ignite. 

Strangely enough, a combination similar to the ammonia catalyst, iron oxide plus alumina, yielded particularly good results (32). Together with Ch. Beck, the author found that other combinations such as iron oxide with chromium oxide, zinc oxide with chromium oxide, lead oxide with uranium oxide, copper oxide with zirconium oxide, manganese oxide with chromium oxide, and similar multicomponent systems were quite effective catalysts for the same reaction (33). 

Calcium. — Digest 20 gm. of copper oxide with a mixture of 5 cc. of nitric acid and 95 cc. of water for about fifteen minutes, shaking frequently filter, precipitate the copper in the filtrate completely by passing hydrogen sulphide gas, and filter again. Evaporate the filtrate on the water-bath to about 20 cc., add ammonia water in excess, filter once more, and to the filtrate add ammonium oxalate solution. No immediate turbidity should be produced. 

Hydrogen gas generated from zinc and hydrochloric acid is passed through a tube containing calcium chloride to remove any water vapor, then over heated copper oxide, with the oxygen of... 

With adjustment of the steam/methane ratio, the reactor can produce a synthesis gas with CO/H2 = 1/2, the stoichiometric proportions needed for methanol production. This mixture at approximately 200 atm pressure is fed to the methanol unit where the reaction then proceeds at 350°C. Per pass conversions range from 30 to 50 over the catalyst— typically a supported copper oxide with a zinc, chromium, or manganese oxide promoter 3... 

Activators Activators selectively react with particles to cause the collector to surface. The classic example, as mentioned above, is the use of copper sulfate for the activation of zinc sulfide so that it can be collected by standard sulfide mineral collectors. Another example is the surfacing of lead carbonate, copper carbonate, and copper oxide with the use of sodium sulfide so that collection is also possible by the sulfide collectors. 

Derivation By treating copper or copper oxide with nitric acid. The solution is evaporated and product recovered by crystallization. 

Problem In order to discuss the reaction with air as an important component, one could heat the copper without air in an evacuated test tube copper remains unchanged after heating in the vacuum. Immediately after this, air is introduced by opening the test tube in the same moment hot copper turns to black copper oxide. With this experiment students should be convinced that the air is responsible for forming the new substance by a chemical reaction. 

Problem This experiment demonstrates that it is possible to regain the red-brown copper from the black copper oxide with the help of hydrogen gas by... 

Procedure Introduce hydrogen gas into the combustion pipe, which contains copper oxide filled in a porcelain boat. If the oxyhydrogen test turns out to be negative, light the hydrogen on the exhaust pipe and heat the copper oxide with a burner. As soon as the reaction sets in, indicated by the formation of metallic copper, remove the burner. Cool down the combustion pipe under a continuous hydrogen stream before the hydrogen supply is turned off. 

The best catalyst was found to consist of zinc oxide and copper (or copper oxide) with an admixture of compounds of chromium. The success of the operation depended upon (a) the absence of alkali, which would cause decomposition of the methanol and the production of higher alcohols and oily products, and (b) the complete elimination of all metals except copper, aluminum and tin from those parts of the apparatus which come in contact with the reacting gases. Contact of carbon monoxide with iron, nickel, or cobalt had to be avoided since they formed volatile carbonyls winch deposited metal, by decomposition, on the active catalyst surface and thereby acted as poisons to destroy activity. 

The senior author et al. (ref. 5) reported previously that the order of rate constant for hydrogen reduction of the preoxidized supported copper oxide with various kinds of reductants were CO > H > CH > C3Hg, and this order was the same as the order of the rate of O2 adsorption to the reduced surfaces with these reductants. This means that the states of the reduced surfaces are changeable with the kinds of reductants suggesting that the importance of the microscopic change of the surface state. 

Cuprous Oxide. Red copper oxide C.I. 77402 Perenex Yellow Cuprocide Copper-Sandoz Caocobre. CujO mol wt 143.08. Cu 88.82%, O 11.18%. Occurs in nature as the mineral cuprite (red to reddisli-brown octahedral or cubic crystals). Prepd commercially by furnace reduction of mixtures ot copper oxides with Cu Drapeau, Johnson, U.S. pats. 2,758,014 2,891,842 (1956, 1959 to Glidden) by decompn of copper ammonium carbonate Rowe, U.S. pat. 2,474,497 Klein, U.S. pat. 2.474,533 (both 1949 to Lake Chemical) Rowe, U.S. pat. 2,536,096, Munn, U.S. pat. 2,670,273 (1951, 1954 to Mountain Copper) by treatment of Cu(OH)j with S02 Rowe, U pat. 2,665,192 (1954 to Mountain Chemical) or by electrolysis of an aq soln of NaCI between Cu electrodes Arend, Paint Technology 13, 265 (1948). Laboratory prepns Glemser, Seuer in Handbook of Preparative Inorganic Chemistry, vol. 2, G. 

When alloyed with small percentages of certain metals (e.g., aluminum, beryllium, iron, silicon, manganese, tin, titanium, and zinc), copper oxidizes with precipitation of oxide particles within the body of the metal as well as forming an outer oxide scale. Oxidation within the metal is called subscale formation or internal oxidation. Similar behavior is found for many silver alloys, but without formation of an outer scale. Internal oxidation is not observed, in general, with cadmium-, lead-, tin-, or zinc-based alloys. A few exceptions have been noted, such as for alloys of sodium-lead, aluminum-tin, and magnesium-tin [44]. Internal oxidation is usually not pronounced for any of the iron alloys. 

---