Binary compounds, sublimation

The binary oxygen-zinc phase diagram is depicted in Fig. 1.5 [58]. Above 200°C only the binary compound ZnO is stable. At low temperatures also zinc peroxide (ZnO2) is reported, which can be prepared by chemical synthesis [59]. The melting point of ZnO is 1975°C. The sublimation of ZnO occurs congruently by decomposition to the gaseous elements according to ... 

L vov and Novichikhin [62] have explored the possibilities of treating decomposition as dissociative sublimation (see Section 2.4.5, for detail). Some of the reactants considered were binary compounds. Magnitudes of calculated for the following reactions ... 

The unsolvated cyclopentadienyl derivatives h -CjHjBeX (X = Cl, Br, I) are prepared by redistribution of the binary compounds [see Eq. (a)] at 50°C in the absence of solvent and isolated and purified by volatilization in vacuo. Stirring Be(C5Hj-h ,h )2 in ether with anhydr FeBrj at — 78°C to RT for 2 h forms volatile h -CjHjBeBr which is separated by sublimation [RT 10" torr (13Nm )] from (h -CjH5)2Fe and unreacted Be(CjH5-h ,h )2. 

All tin(IV) compounds may be obtained by annealing stoichiometric mixtures of the binary tin compounds in closed ampoules. a-Sn2Sl2 can only be obtained free from the /3-phase by applying an excess of Snl2 at a temperature below 350°C (388). An excess of Snl2 cannot be removed from a-Sn2Sl2 by sublimation without transforming the a into the /8 form (388). 

Flood s equation physchem A relation used to determine the liquidus temperature in a binary fused salt system. fladz i.kwa zhan flores CHEM A form of a chemical compound made by the process of sublimation. flor ez 1... 

The evaluation of the sublimation pressure is a problem since most of the compounds to be extracted with the supercritical fluids exhibit sublimation pressures of the order of 10 14 bar, and as a consequence these data cannot be determined experimentally. The sublimation pressure is thus usually estimated by empirical correlations, which are often developed only for hydrocarbon compounds. In the correlation of solubility data this problem can be solved empirically by considering the pure component parameters as fitting-parameters. Better results are obviously obtained [61], but the physical significance of the numerical values of the parameters obtained is doubtful. For example, different pure component properties can be obtained for the same solute using solubility data for different binary mixtures. 

All possible interactions between the K and L groups were taken into account and Akk = 0. The definition contains a minimum number of groups and is satisfactory for most of the binary systems studied. However, it cannot take into account the structural differences which exist between position isomers. This is the case of polycyclic aromatic compounds presenting cycle position isomers or substitute position isomers. Structural differences of this type determine the gaps between the values of certain thermophysical properties of isomers, such as, for example, the fusion temperature or sublimation enthalpy. The further the temperature falls, the more these differences are accentuated. The representation of the solid-fluid (low temperature) equilibria is consequently more difficult and the model must take into account the existing structural differences. We came across this problem in the compounds such as anthracene, phenanthrene, pyrene, methylated naphthalenes, hexamethylbenzene and triphenylmethane. As it was out of the question to increase the number of groups because... 

Compounds of the type [(Me3Si)2N]3M have been prepared for all of the lanthanide elements except Pm, Tb, Dy, Tm, and Er (4). The synthetic method used in their preparation is nucleophilic substitution with three molar equivalents of lithium -or sodium - bis(trimethylsilyl)amide on the metal trichlorides in tetrahydrofuran. The compounds are rather high melting solids (145-170°C) which can be isolated by crystallization from pentane as long needles or by vacuum sublimation (80-100°C). The binary silylamides are monomeric in refluxing benzene solution, in the gas phase (by mass spectrometry), and in the solid state (by x-ray crystallography, see below). Thus, these compounds are three-coordinate, a unique coordination number for the lanthanide elements. 

Binary Systems and Related Compounds.—Halides. The vapourization characteristics of ReBr3 have been studied by effusion techniques and the enthalpy and entropy of sublimation determined as 200 kJ mol and 227 e.u. (per mole of trimer), respectively.The X-ray characteristics of rhenium(iii) iodide, prepared from HRe04 and HI in MeOH at 80-90 °C, have been reported. 

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