Metal gaseous compound

Impurities can be removed by formation of a gaseous compound, as in the fire-refining of copper (qv). Sulfur is removed from the molten metal by oxidation with air and evolution of sulfur dioxide. Oxygen is then removed by reduction with C, CO, in the form of natural gas, reformed... 

Thermodynamic. Thermodynamic properties of Pu metal, gaseous species, and the aqueous ions at 298 K are given in Table 8. Thermodynamic properties of elemental Pu (44), of alloys (68), and of the gaseous ions Pu", PuO", PuO" 27 PuO 2 (67) have been reviewed, as have those of aqueous ions (64), oxides (69), haUdes (70), hydrides (71), and most other compounds (65). 

Unlike bonding, direct boride deposition does not require a reaction with the substrate to form the boride. Both boron and metal atoms are supplied as gaseous compounds. 

Apart from the reactions described above for the formation of thin films of metals and compounds by the use of a solid source of the material, a very important industrial application of vapour phase transport involves the preparation of gas mixtures at room temperature which are then submitted to thermal decomposition in a high temperature furnace to produce a thin film at this temperature. Many of the molecular species and reactions which were considered earlier are used in this procedure, and so the conclusions which were drawn regarding choice and optimal performance apply again. For example, instead of using a solid source to prepare refractory compounds, as in the case of silicon carbide discussed above, a similar reaction has been used to prepare titanium boride coatings on silicon carbide and hafnium diboride coatings on carbon by means of a gaseous input to the deposition furnace (Choy and Derby, 1993) (Shinavski and Diefendorf, 1993). 

An excess of S8( is heated with a metallic element until the metal reacts completely. All excess sulfur is combusted to a gaseous compound and escapes from the crucible. Given the information that follows, determine the most probable formula for the residue. 

Two different instrumental measurements were used to test the oxidation hypothesis GC and atomic absorption (AA). GC was used to determine the chain length distribution of the EO. From the GC results, an average chain length number was calculated. The gas chromatogram is shown in Fig. 21.1. In addition, headspace GC measurement of the gaseous compounds dissolved in the liquid ethoxylate was made and compared to typical or good product. Atomic absorption spectroscopy was used to determine the levels of several trace metals known to catalyze oxidation of fatty chemicals. 

To separate isotopes by this process, they must be in the gaseous form. Therefore, the separation of isolopes of uranium required the conversion of die metallic uranium into a gaseous compound, for which purpose the hexafluoride. UF. was chosen. Since the atomic weight of fluorine is 19, die molecular weight of the hexafluoride of 235 LI is 235 + (6 19) = 349, and the molecular weight of die hexafluoride of 23SU is 238 + (6 x 19) = 352. Since the rate of diffusion of a gas is inversely proportional to die square root of its density (mass per unit volume), the maximum separation factor for one diffusion process of the uranium isotopes is V352/349 = 1.0043, Since only part of the gas can be allowed to diffuse, the, actual separation factoi is even less dian this theoretical maximum. 

Inaba et al. [29] have introduced a different cell to work with gaseous compounds (Fig. 4). A metal-plated solid polymer electrolyte (SPE) composite electrode faces the gas to be reduced. On the other side, the SPE is in contact with 0.1 M NaOH in which a Pt wire and an Ag/AgCl reference electrode are immersed. This system permits the electroreduction of insoluble reactants in water without employing organic solvents. For example, 2-chloro-l,l,l,2-tetrafluoroethane (HCFC 124) is transformed into 1,1,1,2-tetrafluoroethane (HFC 134a). The cathodic reaction can be written as follows ... 

Interesting linear relations were obtained by Golutvin [48] correlating the standard formation enthalpies of solid and gaseous compounds of elements (AH°eq.(g,s), see Equation 44), which are normalized to the oxidation state of the metal ion in this compounds (w) and to the number of metal ions (metal equivalents) in the compounds (eqnwaiXwith the logarithm of the oxidation state of the metal ion in this compounds, see Figure 6. 

The Group IA metal hydroxides are all strong bases with the base strength increasing in going from LiOH to CsOH for the gaseous compounds. 

Nickel occurs, with iron, in meteorites. Its principal ores are nickelite, NiAs, millerite, NiS, and pentlandite, (Ni,Fe)S. The metal is produced, as an alloy containing iron and other elements, by roasting the ore and reducing with carbon. In the purification of nickel by the Mond process the gaseous compound nickel carbonyl, Ni(CO)4, is man ufactured and then decomposed. 

Thallium is obtained as a by-product of the recovery of lead and zinc. Gaseous compounds of the element formed during the recovery process are captured. They are then treated to obtain the pure metal. 

Silicon s most familiar use is in the production of microprocessor chips. Computer microprocessor chips are made from thin slices, or wafers, of a pure silicon crystal. The wafers are doped with elements such as boron, phosphorus, and arsenic to confer semiconducting properties on the silicon. A photographic process places patterns for several chips onto one wafer. Gaseous compounds of metals are allowed to diffuse into the open spots in the pattern, and then the pattern is removed. This process is repeated several times to build up complex microdevices on the surface of the wafer. When the wafer is finished and tested, it is cut into individual chips. 

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