Dicarbides

The salt-like carbides. Among these are aluminium tricarbide imethanide) AI4C3 (containing essentially C ions) in the crystal lattice and the rather more common dicarbides containing the C ion, for example calcium dicarbide CaCjt these carbides are hydrolysed by water yielding methane and ethyne respectively ... 

As a starting material for other deuterocompounds. For example deuterium oxide, on magnesium nitride, gives deutero-ammonia, NDj with calcium dicarbide, deuteroethyne, C2D2, is obtained. 

The solid readily dissolves chemically in concentrated hydrochloric acid, forming a complex, and in ammonia as the colourless, linear, complex cation [H3N -> Cu <- NHj] (cf AgCl) if air is absent (in the presence of air, this is oxidis to a blue ammino-copper(II) complex). This solution of ammoniacal copper(I) chloride is a good solvent or carbon monoxide, forming an addition compound CuCl. CO. H2O, and as such is used in gas analysis. On passing ethyne through the ammoniacal solution, a red-brown precipitate of hydrated copper(I) dicarbide (explosive when dry) is obtained ... 

If ethyne is passed through an ammoniacal solution of silver nitrate, there is a white precipitate of silver dicarbide (cf. copperflH ... 

There are a number of metallic compounds of chromium that ate used either as the compound itself or as metallurgical constituents in Cr-beating alloys. Trichromium dicarbide [12012-35-0] is important as a wear-resistant gauge material chromium botide(l 1) [12006-79-0] CrB, for oil well drilling ... 

The fuel for the Peach Bottom reactor consisted of a uranium-thorium dicarbide kernel, overcoated with pyrolytic carbon and silicon carbide which were dispersed in carbon compacts (see Section 5), and encased in graphite sleeves [37]. There were 804 fuel elements oriented vertically in the reactor core. Helium coolant flowed upward through the tricusp-shaped coolant channels between the fuel elements. A small helium purge stream was diverted through the top of each element and flowed downward through the element to purge any fission products leaking from the fuel compacts to the helium purification system. The Peach... 

The lanthanides (from La to Lu) and yttrium form isomorphous dicarbides with a structure of the CaC2 type (body-centered tetragonal). These lanthanide carbides are known to have conduction electrons (one... 

The criterion based on the vapor pressure holds for actinide Th and U, being non-volatile (their vapor pressures are much lower than La), were recently found to be encapsulated in a form of dicarbide, ThC2[25] and UC2[26], like lanthanide. 

The most ionic of the organometallic derivatives of Group 1 elements are the acetylides and dicarbides formed by the deprotonation of alkynes in liquid ammonia solutions ... 

The largest industrial use of LiC2H is in the production of vitamin A, where it effects ethynyl-ation of methyl vinyl ketone to produce a key tertiary carbinol intermediate. The acetylides and dicarbides of the other alkali metals are prepared similarly. It is not always necessary to prepare this type of compound in liquid ammonia and, indeed, further substitution to give the bright red perlithiopropyne Li4C3 can be effected in hexane under reflux ... 

The C-C distance in CaC2 is close to that in ethyne (120.5 pm) and it has been suggested that the observed increase in the lanthanoid and actin-oid carbides results from a partial localization of the supernumerary electron in the antibonding orbital of the ethynide ion [C=C] (see p. 932). The effect is noticeably less in the sesquicarbides than in the dicarbides. The compounds EuC2 and YbC2 differ in their lattice parameters and hydrolysis behaviour from the other LnC2 and this may be related to the relative stability of Eu and Yb (p. 1237). 

The same reasoning may hold for the virtual absence of transition metal dicarbides with (C2) anions. On the other hand, stable multinary compounds in A-M-(BNx), AE-M-(BNx), or Ln-M-(BNx) systems can exist with an electron-rich transition metal (M), similar to the known ternary dicarbides AM(C2) with A=alkali and M = Pd, Pt [25]. In these cases the valence electrons provided from A or AE metals fill the bonding (BNx)" or (C2) levels, and the transition metal retains an approximate d ° configuration. 

Metal acetylides or carbides Calcium carbide 3.97/46 See Caesium acetylide Mineral acids Rubidium acetylide Acids Uranium dicarbide Hydrogen chloride... 

Lithium acetylide Halogens Monocaesium acetylide Monorubidium acetylide Strontium acetylide Halogens Uranium dicarbide Halogens Zirconium dicarbide Halogens See Monolithium acetylide-ammonia Gases... 

Monocaesium acetylide and caesium acetylide, lithium acetylide and rubidimn acetylide, tungsten carbide and ditungsten carbide, and zirconium dicarbide all ignite in cold fluorine, while uranium dicarbide ignites in warm fluorine. 

Rubidium acetylide ignites on heating, and uranium dicarbide incandesces in the... 

The unit cell dimensions, however, correspond to a = 388 pm, c = 638 pm (c/a = 1.644 instead of 2.463 as in MoSi2) and the free parameter z has the value 0.4068 (instead of 0.333). These differences result in two different space arrangements (see Fig. 3.7). Diatomic groups, such as C2, clearly evident in CaC2 and in a number of isostructural dicarbides and peroxides, are not formed in MoSi2. Very... 

Trimercuiy tetraphosphide, 4616 Tungsten carbide, 0563 Uranium carbide, 0562 Uranium dicarbide, 1028 Zinc phosphide, 4876 Zirconium dicarbide, 1029 METAL PNICTIDES... 

Immiscible wetting in mixers Sol-gel processes Pellet flocculation <0.3 Low Up to 10 tonne/h Wet processing based on flocculation properties of particulate feed Coal fines, soot and oil removal from water Metal dicarbide, silica hydrogels Waste sludges and slurries... 

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