Oxide melts electric conductance

Aluminum metal is produced from aluminum oxide by electrolysis using the Hall-Heroult process, whose story is detailed in our Chemical Milestones Box. The melting point of AI2 O3 is too high (2015 °C) and its electrical conductivity too low to make direct electrolysis commercially viable. Instead, AI2 O3 is mixed with cryolite (Na3 AlFfi) containing about 10% CaF2. This mixture has a melting point of 1000 °C, still a high temperature but not prohibitively so. Aluminum forms several complex ions with fluoride and oxide, so the molten mixture... 

In an individual molten carbamide, the electrode processes are feebly marked at melt decomposition potentials because of its low electrical conductivity. Both electrode processes are accompanied by gas evolution (NH3, CO, C02, N2) and NH2CN (approximately) is formed in melt. In eutectic carbamide-chloride melts electrode processes take place mainly independently of each other. The chlorine must evolve at the anode during the electrolysis of carbamide - alkali metal and ammonium chloride melts, which were revealed in the electrolysis of the carbamide-KCl melt. But in the case of simultaneous oxidation of carbamide and NH4CI, however, a new compound containing N-Cl bond has been found in anode gases instead of chlorine. It is difficult to fully identify this compound by the experimental methods employed in the present work, but it can be definitely stated that... 

Beryllium oxide, BeO, is used in place of Si02 or A1203 in performance-sensitive ceramic applications. It is distinguished by having the highest melting point (2507°C) combined with excellent thermal conductivity and poor electrical conductivity. 

Instead of adhering to the sequence of the periodic table, the pure oxide melts discussed in this section are being broadly divided into three main liquid types. These are the network liquids, the electrically conducting melts and the molecular liquids. It is emphasized that this distinction is not definitive in every case and serves only to illustrate the wide range of liquid properties and structures encountered. 

A summary of most of the early work on conducting oxide melts has been prepared by Van Arkel et al. (57). These results were based primarily on the fusibility of an oxide in an electric arc furnace. Values of the specific conductance of some of these melts at the fusion temperature, with an uncertainty of 50%, estimated by these authors are shown in Table IV. 

The red, amorphous form of vanadium pentoxide is the form most frequently met with in the laboratory. Its preparation has been described above. It melts at 658°10 or 675° C.u to a dark red liquid, but is not volatile even at high temperatures it can be vaporised only in the electric furnace.18 The fused solid conducts electricity, with formation of hypovanadic oxide, V02 18 the electrical conductivity has been measured.14 The oxide absorbs water on exposure to the air, the... 

Biiltemann 2 observed that vanadium ammonium alum separates out in blue crystals from a solution containing sulphuric acid, but from solutions containing a weak acid, or from neutral solutions, red crystals are obtained. (The chromium alums can also be prepared in differently coloured modifications.) The analytical data, melting-point, electrical conductivity, rate of efflorescence, and general behaviour of both kinds of crystals are identical, so that it is difficult to ascribe different constitutions to them. Meyer and Markowitz3 have shown that both forms separate out when the molecular proportion of sulphuric acid in the solution is less than that theoretically required, and attribute the red colour to the presence of traces of vanadous oxide, V203, or its hydroxide, V(OH)3. Vanadium rubidium and vanadium ciesium alums behave in the same way. A vanadium guanidine alum has also been prepared.4... 

Another alloy discovery that transformed an industry was that of nichrome, invented in 1905 by the young American engineer Albert Marsh (1877-1944). Nichrome is an alloy of nickel and chromium that is tough and ductile (capable of being drawn into wires), and very resistant to oxidation and melting with a very low electrical conductivity. These properties make the alloy ideal for a very special application use as wires in a toaster. 

Mg. In vapour phase, unstable Cd2 molecules have been detected (bond energy about 7.4KJmol ). Cd exhibits a certain stability when exposed to dry air, but in the presence of moisture it is slowly covered with an oxide layer. It is softer and more malleable than Zn and can be easily laminated, extruded, drawn, and processed. A characteristic sound (a sort of scream) is generated on bending a bar of the metal. Cd shows a great resistance to corrosion, a low-melting point, and excellent electrical conduction. Unlike zinc, Cd has... 

It has been proposed that the contraction of the electron orbitals in mercury due to Relativistic Effects are important contributors to the element s unusual physical, chemical, and spectroscopic properties. " Some of these properties include the so-called Inert Pair Effect, the difficulty of oxidation of the metal, its unusually low-melting point and electrical conductivity, and the low Enthalpy of vaporization, which at 59.1kJmor is about one-half those of cadmium (100 kJ mol" ) and zinc (114 kJ mol" ). Both NMR shieldings... 

The superiority of the catalyst manufacturing processes that use a molten iron oxide stage is mainly due to the fact that above 1000 °C in air, magnetite, Fe304, is the thermodynamically stable oxide phase of iron [8], [343]. Magnetite leads to especially efficient catalysts, and its electrical conductivity allows the use of economical electrical melting processes. 

The compounds TlYX are insoluble in water and organic solvents. Decomposition with oxidizing acids and bases leads to segregation of the chalcogen. On heating, disintegration into T1(I) halide and chalco-gen takes place between 96 and 132°C (22). The decomposition is incomplete for the chlorides, which form TI4YCI4 321). The electric conductivity of TljS-TlCl melts has been measured 404). 

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