Copper carbonates

Required Sulphuric acid, 3-3 ml. sodium dichromate, 3-5 g. ethanol, 1-5 ml. copper carbonate, 1 5 g. 

Copper carbonates Copper cathode Copper cathodes... 

Alloying elements either enlarge the austenite field or reduce it. The former include manganese, nickel, cobalt, copper, carbon, and nitrogen and are referred to as austenite stabilizers. 

Nonferrous Metal Production. Nonferrous metal production, which includes the leaching of copper and uranium ores with sulfuric acid, accounts for about 6% of U.S. sulfur consumption and probably about the same in other developed countries. In the case of copper, sulfuric acid is used for the extraction of the metal from deposits, mine dumps, and wastes, in which the copper contents are too low to justify concentration by conventional flotation techniques or the recovery of copper from ores containing copper carbonate and siUcate minerals that caimot be readily treated by flotation (qv) processes. The sulfuric acid required for copper leaching is usually the by-product acid produced by copper smelters (see Metallurgy, extractive Minerals RECOVERY AND PROCESSING). 

Palladium and platinum (5—10 wt % on activated carbon) can be used with a variety of solvents as can copper carbonate on siHca and 60 wt % nickel on kieselguhr. The same is tme of nonsupported catalysts copper chromite, rhenium (VII) sulfide, rhenium (VI) oxide, and any of the Raney catalysts, copper, iron, or nickel. 

Basic copper carbonate is essentially iasoluble ia water, but dissolves ia aqueous ammonia or alkaU metal cyanide solutions. It dissolves readily ia mineral acids and warm acetic acid to form the corresponding salt solution. 

Cupric chloride or copper(II) chloride [7447-39 ], CUCI2, is usually prepared by dehydration of the dihydrate at 120°C. The anhydrous product is a dehquescent, monoclinic yellow crystal that forms the blue-green orthohombic, bipyramidal dihydrate in moist air. Both products are available commercially. The dihydrate can be prepared by reaction of copper carbonate, hydroxide, or oxide and hydrochloric acid followed by crystallization. The commercial preparation uses a tower packed with copper. An aqueous solution of copper(II) chloride is circulated through the tower and chlorine gas is sparged into the bottom of the tower to effect oxidation of the copper metal. Hydrochloric acid or hydrogen chloride is used to prevent hydrolysis of the copper(II) (11,12). Copper(II) chloride is very soluble in water and soluble in methanol, ethanol, and acetone. 

Below silt accumulations on copper, brass, and cupronickel heat exchangers, a layer of bluish-white copper carbonate often forms (Figs. 4.14 and 4.15). 

Calcium carbonate has normal pH and inverse temperature solubilities. Hence, such deposits readily form as pH and water temperature rise. Copper carbonate can form beneath deposit accumulations, producing a friable bluish-white corrosion product (Fig. 4.17). Beneath the carbonate, sparkling, ruby-red cuprous oxide crystals will often be found on copper alloys (Fig. 4.18). The cuprous oxide is friable, as these crystals are small and do not readily cling to one another or other surfaces (Fig. 4.19). If chloride concentrations are high, a white copper chloride corrosion product may be present beneath the cuprous oxide layer. However, experience shows that copper chloride accumulation is usually slight relative to other corrosion product masses in most natural waters. 

Figure 4.15 As in Fig. 4.14 but with silt removed to reveal bluish-white copper carbonate corrosion products. 

Figure 4.17 Corroded copper tubes from a heating coil. Cooling water contacted the visible surface. The mounds consist of copper carbonate (see Fig. 4.18).

Numerous failures of the tjrpe illustrated in Fig. 9.22 had occurred over a period of months. External surfaces are visually smooth, uncorroded, and covered with a thin layer of deposit. Internal surfaces are covered with a coating of copper carbonate. 

Avoid using copper-based compounds such as copper carbonate. Copper can plate out on steel and set up galvanic corrosion cells, resulting in accelerated corrosion of the steel. 

Finally, a book has recently been published covering corrosion problems related to nuclear waste disposal" . It discusses a variety of subjects including corrosion behaviour and SCC of copper, carbon steels and high alloy steels under conditions related to nuclear waste disposal. Special attention is paid to pitting and problems associated with hydrogen gas generation from corrosion processes. 

Typically the internals of the coil show pits and pinholes and may even perforate. Corrosion debris is evident, usually containing green hydrated copper carbonate (CuC03 nH20) and red cuprous oxide (Cu20). 

Problems with heating coils Internal coil corrosion Note corrosion debris is green hydrated copper carbonate Cu[11IC03 nH20 red cuprous oxide Cu20 /ntemal coil deposition Acid corrosion from soft water. Pinhole corrosion from 02 and C02. Erosion corrosion over 6 ft/s flow. Hard water scale from hard water. 

However, even when this is successful there remains a serious problem. Dense carbon is very porous. Even if the surface is not wetted by the electrolyte, below about a 10-cm depth there is enough hydrostatic pressure to push electrolyte into the pores and into the copper/carbon interface. When the electrolyte reaches it, the copper corrodes. Since the corrosion products occupy more volume than the copper, the carbon is put under tensile stress and fails by cracking. 

The pale green product is called basic copper carbonate and is responsible for the green patina of copper and bronze objects (Fig. 16.13). The patina adheres to the surface, protects the metal, and has a pleasing appearance. 

FIGURE 16.13 Copper corrodes in air to form an attractive pale green layer of basic copper carbonate. This patina, or incrustation, passivates the surface, which helps to protect it from further corrosion. 

The reddish metal was already known in prehistoric times. It occasionally occurs as a native metal, but mostly in conspicuous green ores, from which it is extracted relatively easily. It is convenient to work, but not very hard. Not very optimal as a tool ("Otzi the Iceman" had a copper axe with him). Only through the addition of tin is the more useful bronze obtained. Its zinc alloy is the versatile and widely used brass. Copper is one of the coinage metals. Water pipes are commonly made of copper. Its very good thermal and electrical conductivity is commonly exploited (cable ), as well as its durability (roofs, gutters), as the verdigris (basic copper carbonate) protects the metal. Cu phthalocyanines are the most beautiful blue pigments. Seems to be essential to all life as a trace element. In some molluscs, Cu replaces Fe in the heme complex. A 70-kg human contains 72 mg. 

Azurite Hydrous copper carbonate Blue 3.8 3.8 Crystalline Ornamental stone, gemstone, blue pigment, building stone, making lime... 

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