Halide containing gases

The initial pulsed electron irradiation of a rare gas (R) produces excited states (R ), ions (R" ) and a range of secondary electrons (e s) and by addition of a trace amount of a halide containing gas (AX), whose concentration is small enough that there is no direct excitation by the primary electron beam, exciplex (RX ) formation occurs as follows ... 

Information published from several sources about 1970 presented details on both the halide-containing RhCl(CO)(PPh3)2- and the hydride-containing HRh(CO)(PPh3)3-catalyzed reactions. Brown and Wilkinson (25) reported the relative rates of gas uptake for a number of different olefinic substrates, including both a- and internal olefins. These relative rates are listed in Table XV. 1-Alkenes and nonconjugated dienes such as 1,5-hexadiene reacted rapidly, whereas internal olefins such as 2-pentene or 2-heptene reacted more slowly by a factor of about 25. It should also be noted that substitution on the 2 carbon of 1-alkene (2-methyl-l-pentene) drastically lowered the rate of reaction. Steric considerations are very important in phosphine-modified rhodium catalysis. 

For comparative purposes, calculated boron and gallium shielding tensors of their respective hydrides and halides were also investigated at the RHF level of theory with the 6-311 G(d,p) basis set, which was the largest available for all the elements involved, with the exception of iodine for which a [10s,8p,4d] basis set (48) with two sets of f functions (orbital exponents of 4.0 and 1.0) (49) was used. Calculations were also performed at the MP2 level, except for molecules containing Ga, Br and I. 

The only known halides containing Co(III) and Co(IV) are the fluorides. C0F4 is formed in low yield in the gas... 

Oxidation and hydrolysis reactions are two common methods of producing oxide films. In this class of reaction, the metal precursor contains metal atoms in a reduced valence state, usually a metal hydride or metal halide. The oxidizing agent is an oxygen containing gas such as O2, O3, CO2, H2O, or N2O. The reaction is a simple oxidation scheme. Examples of such reactions are ... 

Light retards the reactions of PbNa and of lead-sodium-potassium alloys with C2H5CI and this effect is increased by addition of water to the gas phase. Reaction products are assumed to impede penetration of light to the reacting surface of the alloy [267]. The gases produced in the reaction of lead-sodium alloys with ethyl halides contain, aside from C2H6 as the main product, C2H4, n-butane, propane, and minor amounts of other... 

Combustion Many organic compounds released from manufacturing operations can be converted to innocuous carbon dioxide and water by rapid oxidation (chemical reaction) combustion. However, combustion of gases containing halides may require the addition of acid gas treatment to the combustor exhaust. 

Use of some biomass feedstocks can increase potential environmental risks. Municipal solid waste can contain toxic materials that can produce dioxins and other poisons in the flue gas, and these should not be burned without special emission controls. Demolition wood can contain lead from paint, other heavy metals, creosote, and halides used in presen a-tive treatments. Sewage sludge has a high amount of sulfur, and sulfur dioxide emission can increase if sewage sludge is used as a feedstock. 

Typically, Be-containing alloys and intermetallic phases have been prepared in beryllia or alumina crucibles Mg-containing products have been synthesized in graphite, magnesia or alumina crucibles. Alloys and compounds containing Ca, Sr and Ba have been synthesized in alumina , boron nitride, zircon, molybdenum, iron , or steel crucibles. Both zircon and molybdenum are satisfactory only for alloys with low group-IIA metal content and are replaced by boron nitride and iron, respectively, for group-IIA metal-rich systems . Crucibles are sealed in silica, quartz, iron or steel vessels, usually under either vacuum or purified inert cover gas in a few cases, the samples were melted under a halide flux . 

As a result of their reactivity, particular attention must be given to preparation and purification of the metals, the conditions under which the metals, alloys and compounds are handled and the choice of material for the containment vessel. Ultrapure group-IIB metals may be used without further purification, but it is advisable to purify the group-IIA metals by a multidistillation process, the final distillation preferably being carried out in situ. The reactants and products are best handled in an atmosphere of a purified inert gas, usually He or Ar (N2 cannot be used because of the ready formation of group-IIA metal nitrides) alternatively, they can be handled under vacuum or, in rare cases, under halide fluxes. The containment vessel is normally fabricated from a refractory. 

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