Oxide cuprous

Cuprous oxide is also manufactured electrolytically but on a much smaller scale. Around the world, there are several plants producing 200—500 ton yr. In this case the oxide results from direct oxidation of the metal in an alkaline medium 

The electrolyte also contains chloride ion as a pitting agent to prevent passivation of the anode surface (see Chapter 9). 

Mantell, C. L. I960) Electrochemical Engineering, McGraw-Hill, New York. 

) 91 ) Industrial Electrochemical Processes, Elsevier, London. 

Schmidt, A. (1916) Angewandte Electrochemie, Verlag Chemie, Weinheim. 

The actual electrode processes are complex in simple terms the main reactions may be described by  

At frequent intervals during the electrolysis the cell polarity is automatically reversed such that each of the copper electrodes is the anode for half of its lifetime in the cell. This strategy prevents passivation of the anodes and helps provide a more uniform product. In some cells, manual scraping of the electrodes is also used. 

The ceils are operated on a batch basis cuprous oxide falls from the anodes to the bottom of the tanks. At suitable intervals, the electrolysis is stopped, the residual electrodes removed for remelting, and the Cu O-NaCI slurry is agitated and pumped out of the cell for external separation of CujO  

There is a growing awareness that electrochemical methods of synthesis may be used to achieve controUed purity compounds which are difficult to produce by chemical or thermal methods. A general strategy for the synthesis of metal salts or complexes is controlled anodic dissolution of the pure metal in a suitable electrolyte. In a simple case, the anode process may be the formation of a soluble, hydrated metal ion (as in electro refining, section 4,3)  

In the potassium stannate process shown schematically in Fig. 5.16 the anode is a steel basket filled with solid tin bars or pellets immersed In KOH solution. Under suitable conditions, the tin dissolves as stannitc  

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Add 2 -3 drops of phenylhydrazine to about 2 ml. of Fehling s solution in a test-tube and shake the mixture vigorously nitrogen is evolved and reddish-brown cuprous oxide is precipitated. The reaction proceeds rapidly on gentle warming, more slowly in the cold. 

The colour of the precipitate depends upon the size of the cuprous oxide particles, and this in turn upon the rate of reduction, concentration of the solution, etc. 

Reduction of Fehling s solution. Add 5 ml. of the glucose solution to 5 ml. of Fehling s solution and boil. Reduction takes place and a precipitate of cuprous oxide is formed the latter is at first yellow but may become red on standing. 

Reduction of Fehling s solution. Boil i ml. of chloroform gently with 3 ml. of Fehling s solution with constant shaking for 3-4 minutes. Reduction occurs and reddish cuprous oxide slowly separates. 

Disappearance of the deep blue colour and precipitation of cuprous oxide indicates reducing agents such as ... 

Several variations of the chemical method are in use. In the one described below, a freshly prepared Fehling s solution is standardised by titrating it directly against a standard solution of pure anhydrous glucose when the end-point is reached, I. e., when the cupric salt in the Fehling s solution is completely reduced to cuprous oxide, the supernatant solution becomes completely decolorised. Some difficulty is often experienced at first in determining the end-point of the reaction, but with practice accurate results can be obtained. The titrations should be performed in daylight whenever possible, unless a Special indicator is used (see under Methylene-blue, p. 463). 

Dissolve 0-5 g. of the substance in 10 ml. of 50 per cent, alcohol, add 0-5 g. of solid ammonium chloride and about 0 -5 g. of zinc powder. Heat the mixture to boiling, and allow the ensuing chemical reaction to proceed for 5 minutes. Filter from the excess of zinc powder, and teat the filtrate with Tollen s reagent Section 111,70, (i). An immediate black or grey precipitate or a silver mirror indicates the presence of a hydroxyl-amine formed by reduction of the nitro compound. Alternatively, the filtrate may be warmed with Fehling s solution, when cuprous oxide will be precipitated if a hydroxylamine is present. Make certain that the original compound does not aflfect the reagent used. 

The Reaction. Acrolein has been produced commercially since 1938. The first commercial processes were based on the vapor-phase condensation of acetaldehyde and formaldehyde (1). In the 1940s a series of catalyst developments based on cuprous oxide and cupric selenites led to a vapor-phase propylene oxidation route to acrolein (7,8). In 1959 Shell was the first to commercialize this propylene oxidation to acrolein process. These early propylene oxidation catalysts were capable of only low per pass propylene conversions (ca 15%) and therefore required significant recycle of unreacted propylene (9—11). 

Early catalysts for acrolein synthesis were based on cuprous oxide and other heavy metal oxides deposited on inert siHca or alumina supports (39). Later, catalysts more selective for the oxidation of propylene to acrolein and acrolein to acryHc acid were prepared from bismuth, cobalt, kon, nickel, tin salts, and molybdic, molybdic phosphoric, and molybdic siHcic acids. Preferred second-stage catalysts generally are complex oxides containing molybdenum and vanadium. Other components, such as tungsten, copper, tellurium, and arsenic oxides, have been incorporated to increase low temperature activity and productivity (39,45,46). 

Less activated substrates such as uorohaloben2enes also undergo nucleophilic displacement and thereby permit entry to other useful compounds. Bromine is preferentially displaced in -bromofluoroben2ene [460-00-4] by hydroxyl ion under the following conditions calcium hydroxide, water, cuprous oxide catalyst, 250°C, 3.46 MPa (500 psi), to give -fluorophenol [371-41-5] in 79% yield (162,163). This product is a key precursor to sorbinil, an en2yme inhibitor (aldose reductase). 

Lithium is used in metallurgical operations for degassing and impurity removal (see Metallurgy). In copper (qv) refining, lithium metal reacts with hydrogen to form lithium hydride which subsequendy reacts, along with further lithium metal, with cuprous oxide to form copper and lithium hydroxide and lithium oxide. The lithium salts are then removed from the surface of the molten copper. 

Amino-l-naphthalenecarboxyhc acid can be converted, by dia2oti2ation and treatment with ammoniacal cuprous oxide, to l,l -binaphthalene-8,8 -dicarboxyhc acid [29878-91-9] (48). Treatment of (48) with concentrated sulfuric acid yields anthranthrone. The dihalogenated anthranthrones are valuable vat dyes. 

Propylene oxide is also produced in Hquid-phase homogeneous oxidation reactions using various molybdenum-containing catalysts (209,210), cuprous oxide (211), rhenium compounds (212), or an organomonovalent gold(I) complex (213). Whereas gas-phase oxidation of propylene on silver catalysts results primarily in propylene oxide, water, and carbon dioxide as products, the Hquid-phase oxidation of propylene results in an array of oxidation products, such as propylene oxide, acrolein, propylene glycol, acetone, acetaldehyde, and others. 

These chemical composition requirements pertain only to the cuprous oxide powder and do not include requirements for the organic vehicle in which the cuprous oxide is suspended, when appHed in paste form. 

Ofner Method. This method is for the determination of invert sugar in products with up to 10% invert in the presence of sucrose and is a copper-reduction method that uses Ofner s solution instead of Fehling s. The reduced cuprous oxide is treated with excess standardized iodine, which is black-titrated with thiosulfate using starch indicator. 

Colorimetric Methods. Numerous colorimetric methods exist for the quantitative determination of carbohydrates as a group (8). Among the most popular of these is the phenol—sulfuric acid method of Dubois (9), which rehes on the color formed when a carbohydrate reacts with phenol in the presence of hot sulfuric acid. The test is sensitive for virtually all classes of carbohydrates. Colorimetric methods are usually employed when a very small concentration of carbohydrate is present, and are often used in clinical situations. The Somogyi method, of which there are many variations, rehes on the reduction of cupric sulfate to cuprous oxide and is appHcable to reducing sugars. 

Copper Corrosion Inhibitors. The most effective corrosion inhibitors for copper and its alloys are the aromatic triazoles, such as benzotriazole (BZT) and tolyltriazole (TTA). These compounds bond direcdy with cuprous oxide (CU2O) at the metal surface, forming a "chemisorbed" film. The plane of the triazole Hes parallel to the metal surface, thus each molecule covers a relatively large surface area. The exact mechanism of inhibition is unknown. Various studies indicate anodic inhibition, cathodic inhibition, or a combination of the two. Other studies indicate the formation of an insulating layer between the water surface and the metal surface. A recent study supports the idea of an electronic stabilization mechanism. The protective cuprous oxide layer is prevented from oxidizing to the nonprotective cupric oxide. This is an anodic mechanism. However, the triazole film exhibits some cathodic properties as well. 

Copper(I) oxide [1317-39-1] is 2lp-ty e semiconductor, Cu2 0, in which proper vacancies act as acceptors to create electron holes that conduct within a narrow band in the Cu i7-orbitals. Nickel monoxide [1313-99-17, NiO, forms a deficient semiconductor in which vacancies occur in cation sites similar to those for cuprous oxide. For each cation vacancy two electron holes must be formed, the latter assumed to be associated with regular cations ([Ni " h = Semiconduction results from the transfer of positive charges from cation to cation through the lattice. Conduction of this type is similar... 

CllO. The most common commercial purity copper is CllO. The principal difference between CllO and C102 is oxygen content which typically can be up to 0.05% in CllO. Oxygen is present as cuprous oxide particles, which do not significantly affect strength and ductiHty, but CllO is susceptible to hydrogen embrittlement. The properties of CllO are adequate for most appHcations and this alloy is less cosdy than higher purity copper. 

The copper(I) ion, electronic stmcture [Ar]3t/ , is diamagnetic and colorless. Certain compounds such as cuprous oxide [1317-39-1] or cuprous sulfide [22205-45 ] are iatensely colored, however, because of metal-to-ligand charge-transfer bands. Copper(I) is isoelectronic with ziac(II) and has similar stereochemistry. The preferred configuration is tetrahedral. Liaear and trigonal planar stmctures are not uncommon, ia part because the stereochemistry about the metal is determined by steric as well as electronic requirements of the ligands (see Coordination compounds). 

Special containers have been developed for anesthetic ether to prevent deterioration before use. Their effectiveness as stabHizers usuaHy depends on the presence of a lower oxide of a metal having more than one oxidation state. Thus the sides and the bottoms of tin-plate containers are electroplated with copper, which contains a smaH amount of cuprous oxide. Staimous oxide is also used in the linings for tin containers. Instead of using special containers, iron wire or certain other metals and aHoys or organic compounds have been added to ether to stabHize it. 

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