Copper zinc ratio

It should not be assumed that the composition of commercial alloys will necessarily correspond to the percentages indicated or that other metals may not be present in small amounts. For example, the properties of brass differ with variation in the copper-zinc ratio. Similarly, the properties of commercial brass are often profoundly changed by the presence of small quantities of other metals. Since alloys are usually fabricated from metals that have not been subjected to elaborate purification processes, the resulting alloys are frequently contaminated with metals present in the primary ores. 

Poo, J.L., Rosas-Romero, R., Montemayor, A.C., Isoard, F., Uribe, M. Diagnostic value of the copper/zinc ratio hepatocellular carcinoma a case control study. J. Gastroenterol. 2003 38 45- 51... 

Single metals and alloys such as wrought iron, bronze and lead will corrode even though they are not joined to a different metal or alloy. In reality, anodes and cathodes are set up on the surface of the metal. This will be due to the different phases present in the alloy, e.g. iron (ferrite) will be the anode and graphite the cathode in a cast iron, impurities such as sulfides present in wrought iron and variation in the copper/zinc ratio in adjacent grains in a brass alloy. The reactions taking place on the anode and cathode will be the same except the anode may be a different metal if the object was not iron. With a copper artefact, for example, the anode reaction will be ... 

For a copper/zinc ratio of 1 1 (x = 0.5, CuZn), the face centered cubic structure is no longer stable and transforms into a body centered cubic structure, the P-Phase... 

The commonest alloy to be electroplated is brass, which may be obtained in a wide range of copper-zinc ratios from cyanide baths. Surface coatings consisting of alloys of copper and cadmium, or containing tin, zinc and nickel, have also been produced. 

High pressure processes P > 150 atm) are catalyzed by copper chromite catalysts. The most widely used process, however, is the low pressure methanol process that is conducted at 503—523 K, 5—10 MPa (50—100 atm), space velocities of 20, 000-60,000 h , and H2-to-CO ratios of 3. The reaction is catalyzed by a copper—zinc oxide catalyst using promoters such as alumina (31,32). This catalyst is more easily poisoned than the older copper chromite catalysts and requites the use of sulfiir-free synthesis gas. 

In a mixed copper-zinc solution of complex cyanide, however, the Cu ion concentration can be reduced to the order of lO mol/L and the concentration ratio (zinc ion)/(copper ion) will be made very large. A detailed calculation for this case is given by Faust in the 1974 edition of Modem Electroplating (1). It is shown there, and in detail below, that the copper cyanide complex is Cu(CN)3 , for which the dissociation value is known. The dissociation constant for the zinc cyanide complex, Zn(CN)4 , is also well known. Using those values that determine the fraction concentration of the free metal ion in solution and assuming an initial specific molar concentration, it is shown below that their respective reversible electrode potentials [see also Eq. (11.1)] can be brought together. 

Adjustment of the C0 H2 ratio is effected by the shift reaction (iv) which proceeds over a chromium-promoted iron catalyst at 700-800°F (370-425°C) or over a reduced copper/zinc catalyst at 375" 50°F (190-230 C) and the fraction of crude gas sent through the shift reactor is calculated from the initial gas composition and specific downstream requirements. The latter are i1 lustrated by... 

Shape-memory alloys (e.g. Cu-Zn-Al, Fe-Ni-Al, Ti-Ni alloys) are already in use in biomedical applications such as cardiovascular stents, guidewires and orthodontic wires. The shape-memory effect of these materials is based on a martensitic phase transformation. Shape memory alloys, such as nickel-titanium, are used to provide increased protection against sources of (extreme) heat. A shape-memory alloy possesses different properties below and above the temperature at which it is activated. Below this temperature, the shape of the alloy is easily deformed due to its flexible structure. At the activation temperature, the alloy can be changed by applying a force, but the structure resists this deformation and returns back to its initial shape. The activation temperature is a function of the ratio of nickel to titanium in the alloy. In contrast with Ni-Ti, copper-zinc alloys are capable of a two-way activation, and therefore a reversible variation of the shape is possible, which is a necessary condition for protection purposes in textiles used to resist changeable weather conditions. 

Brass (copper + zinc) and bronze (copper + tin) are the most common and widely used alloys of copper. There are many different formulae for these alloys, and the percentages of each metal used varied according to the properties that were desired in the end product, and what was available to the metal workers in a given place. German silver is another copper-based alloy (Cu + Ni + Zn). Lattan is a copper-based alloy used for casting, but the ratios of its component metals are uncertain. 

Quantitative and qualitative changes in chemisorption of the reactants in methanol synthesis occur as a consequence of the chemical and physical interactions of the components of the copper-zinc oxide binary catalysts. Parris and Klier (43) have found that irreversible chemisorption of carbon monoxide is induced in the copper-zinc oxide catalysts, while pure copper chemisorbs CO only reversibly and pure zinc oxide does not chemisorb this gas at all at ambient temperature. The CO chemisorption isotherms are shown in Fig. 12, and the variations of total CO adsorption at saturation and its irreversible portion with the Cu/ZnO ratio are displayed in Fig. 13. The irreversible portion was defined as one which could not be removed by 10 min pumping at 10"6 Torr at room temperature. The weakly adsorbed CO, given by the difference between the total and irreversible CO adsorption, correlated linearly with the amount of irreversibly chemisorbed oxygen, as demonstrated in Fig. 14. The most straightforward interpretation of this correlation is that both irreversible oxygen and reversible CO adsorb on the copper metal surface. The stoichiometry is approximately C0 0 = 1 2, a ratio obtained for pure copper, over the whole compositional range of the... 

Fig. 13. The dependence of the carbon monoxide saturation adsorption (total) and irreversible adsorption (irreversible) on the Cu/ZnO ratio in the binary copper-zinc oxide catalysts...

Germanium minerals are extremely rare but the element is widely distribnted in trace amounts. Its abundance ratio is about 7 x 10 % and it is mainly associated with copper, zinc, lead, selenium, arsenic, silver, iron, and so on. There are twenty-one isotopes Ge, Ge, Ge, Ge, Ge are naturally occurring. Germaiuum is common in organisms, but it is not an indispensable trace element. In humans, it is nontoxic, but when it reaches 1000 ppm in animal s food, the growth of animals wifi be inhibited and 50% of them will die. 

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