Cadmium dissolved

In relation to the separation of cadmium from zinc by volatilization, it is worth noting that the ratio Pcd/P2n increases with decreasing temperature (from 5.09 at 850 °C to 7.30 at 650 °C and 12.69 at 450 °C). The liquid solution of zinc and cadmium exhibits a regular solution behavior and, therefore, the activity coefficient of cadmium dissolved in liquid zinc increases with decreasing temperature. Both these features suggest that the elimination of cadmium from zinc is more efficient at relatively lower temperatures. This is reflected in the choice of the temperatures in the second column. 

Toxicity. Cadmium pigments are cadmium compounds with a low solubility, however, small quantities of cadmium dissolve in dilute hydrochloric acid (concentration equivalent to stomach acid), and in cases of long-term oral intake of cadmium pigments, they can accumulate in the human body. On inhalation of subchronic amounts of cadmium pigments, a small proportion of cadmium is biologically available [3.115], [3.116]. 

Zinc and cadmium dissolve in dilute acid to give their -I- 2 ions, but mercury does not dissolve, as indicated by the two positive reduction potentials. Mercury forms the diatomic Hg2 ion, in which the Hg-Hg bond length is 251 pm, consistent with it being a single ct bond formed from the overlap of the two 6s atomic orbitals. The reason for the relatively greater stability of the 6s electrons of Hg is relativistic stabilization which causes the first two ionization energies (1010 and 1810 kJ mol ) to be considerably greater than those of Zn (908 and 1730 kJ mol ) and Cd (866 and 1630 kJ mol ). 

As illustrated in Figure 7.1, tap water itself is a solution containing many things. It has some dissolved oxygen and carbon dioxide in it. It almost certainly has some dissolved calcium compounds, making it hard. There may be a small amount of iron present, which causes the water to stain clothing. It contains some chlorine, added to kiU bacteria. In unfavorable cases, it may even contain some toxic lead and cadmium dissolved from plumbing and the solder used to connect copper pipes. Thus, it is clear that many of the liquids that people come in contact with are actually solutions. 

The weak acid scrubbing liquor is bled from the system to maintain either a preset maximum acidity or a maximum fluorine concentration. Otherwise the bleed will merely be set by the water balance control. This solution also contains lead, zinc and cadmium dissolved from sinter dusts as well as mercury and selenium. Mercury and selenium react to form mercuric selenide, which precipitates and can foul heat transfer surfaces. The presence of selenium can be beneficial in increasing the capture of mercury by the gas scrubbing system. 

Cadmium dissolves readily in HNO3, releasing nitrogen oxides. The acid also dissolves all well-known compoimds of Cd as at least CdNOs. ... 

Cadmium dissolves in NH4NO3 quietly, producing no gas, possibly as ... 

Cadmium dissolves slowly in hot, rather dilute H28O4, releasing H2 and forming at least Cd804 and Cd(804)2 complexes. 

While studying the electrolysis of ethereal solutions of a Grignard reagent, French and Drane [55] observed that anodes of aluminum, zinc, and cadmium dissolved and that these metals were deposited at the cathode. More recently Evans [56] proposed that triethylaluminum is formed when an aluminum anode dissolves in ethylmagnesium bromide ... 

Unlike cadmium and mercury and, in fact, all metals of Group II, zinc dissolves readily in alkalis forming zincates. in which the zinc atom is contained in a complex hydroxo-anion, for example ... 

Cadmium is a soft metal, which forms a protective coating in air, and burns only on strong heating to give the brown oxide CdO. It dissolves in acids with evolution of hydrogen ... 

Fused-salt electrolysis of K2NbFy is not an economically feasible process because of the low current efficiency (31). However, electrowinning has been used to obtain niobium from molten alkaU haUde electrolytes (32). The oxide is dissolved in molten alkaU haUde and is deposited in a molten metal cathode, either cadmium or zinc. The reaction is carried out in a ceramic or glass container using a carbon anode the niobium alloys with the cathode metal, from which it is freed by vacuum distillation, and the niobium powder is left behind. 

Henkel Rearrangement of Benzoic Acid and Phthalic Anhydride. Henkel technology is based on the conversion of benzenecarboxyhc acids to their potassium salts. The salts are rearranged in the presence of carbon dioxide and a catalyst such as cadmium or zinc oxide to form dipotassium terephthalate, which is converted to terephthahc acid (59—61). Henkel technology is obsolete and is no longer practiced, but it was once commercialized by Teijin Hercules Chemical Co. and Kawasaki Kasei Chemicals Ltd. Both processes foUowed a route starting with oxidation of napthalene to phthahc anhydride. In the Teijin process, the phthaHc anhydride was converted sequentially to monopotassium and then dipotassium o-phthalate by aqueous recycle of monopotassium and dipotassium terephthalate (62). The dipotassium o-phthalate was recovered and isomerized in carbon dioxide at a pressure of 1000—5000 kPa ( 10 50 atm) and at 350—450°C. The product dipotassium terephthalate was dissolved in water and recycled as noted above. Production of monopotassium o-phthalate released terephthahc acid, which was filtered, dried, and stored (63,64). 

Modifications to Precipitates. Silicon is sometimes added to Al—Cu—Mg alloys to help nucleate S precipitates without the need for cold work prior to the elevated temperature aging treatments. Additions of elements such as tin [7440-31-5] Sn, cadmium [7440-43-9] Cd, and indium [7440-74-6] In, to Al—Cu alloys serve a similar purpose for 9 precipitates. Copper is often added to Al—Mg—Si alloys in the range of about 0.25% to 1.0% Cu to modify the metastable precursor to Mg2Si. The copper additions provide a substantial strength increase. When the copper addition is high, the quaternary Al CuMg Si Q-phase must be considered and dissolved during solution heat treatment. 

Aeration must be avoided since it can oxidize and resolubiUze the cemented (precipitated) impurities. Filter presses are used after each step and the cakes are leached to recover various values. For example, cadmium is dissolved, recemented with zinc, and recovered on site either electrolyticaHy or by distillation. A copper residue of 25—60% copper is sold for recovery elsewhere. The other impurities cannot be recovered economically with the exception of cobalt in some plants. 

Air pollution problems and labor costs have led to the closing of older pyrometaHurgical plants, and to increased electrolytic production. On a worldwide basis, 77% of total 2inc production in 1985 was by the electrolytic process (4). In electrolytic 2inc plants, the calcined material is dissolved in aqueous sulfuric acid, usually spent electrolyte from the electrolytic cells. Residual soHds are generally separated from the leach solution by decantation and the clarified solution is then treated with 2inc dust to remove cadmium and other impurities. 

The autoclave is cooled to room temperature, and the carbon dioxide is bled off. The solid reaction product is taken from the autoclave, pulverized, and dissolved in 1 1. of water at 50-60°. Ten grams of decolorizing carbon is added, and the mixture is stirred well and filtered to remove cadmium salts and carbon. The filtrate is heated to 80-90° and acidified with concentrated hydrochloric acid to pH 1 (Note 5). 2,6-Naphthalenedicar-boxylic acid precipitates. It is separated from the hot mixture by filtration. It is then suspended in 500 ml. of water at 90-95° (Note 5), separated by filtration, and washed successively with 300 ml. of water, 300 ml. of 50% ethanol, and 300 ml. of 90% ethanol. After being dried at 100-150°/150 mm. in a vacuum oven, the 2,6-naphthalenedicarboxylic acid weighs 42-45 g. (57-61%). It decomposes on a heated block at 310-313°. 

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