Molecular structure of metal halides.

The second part of this compendium concludes with a collection of phase change enthalpies of organic molecules inclusive of C11–C192 reported over the period 1880–2015. Also included are phase change enthalpies including fusion, vaporization, and sublimation enthalpies for organometallic, ionic liquids, and a few inorganic compounds. Paper I of this compendium, published separately, includes organic compounds from C1 to C10 and describes a group additivity method for evaluating solid, liquid, and gas phase heat capacities as well as temperature adjustments of phase changes. Paper II of this compendium also includes an updated version of a group additivity method for evaluating total phase change entropies which together with the fusion temperature can be useful in estimating total phase change enthalpies. Other uses include application in identifying potential substances that either form liquid or plastic crystals or exhibit additional phase changes such as undetected solid–solid transitions or behave ani...

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Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds and Ionic Liquids. Sublimation, Vaporization, and Fusion Enthalpies from 1880 to 2015. Part 2. C11–C192

The chemistry of inorganic vapors is for the most part the chemistry of high-temperature vapors. This article essentially reports on the gaseous species observed in the equilibrium vapors and their dissociation or atomization energies. Most of the results were obtained by Knudsen effusion mass spectrometry. The fundamentals of this method are described with respect to the recent methodic developments. Accounts of the investigations of metals, alloys, oxides, metal halides, and technical materials are given and the results are reviewed. Vaporization processes and thermochemical properties of condensed phases evaluated from gas phase data are also considered. The results are for example of interest for the active fields of energy, high-temperature materials, and cluster research. An extended summary with outlook is given in Sect. 7-“Summary and conclusions”-of this article.

Chemistry of inorganic vapors

Electron capture and energy loss in ∼100 keV collisions of atomic and molecular ions on C60

Absorption cross sections of gas phase and in the 40 000 to region have been determined. The results are based on the combination of absorbance measurements of fullerene vapour, produced by the sublimation of samples in quartz double cells, and the vapour pressure measurements of the literature for solvent-free solid fullerenes. The gas phase cross sections are compared to those derived from molar extinction coefficients of and in hexane solutions and highlight the problems associated with the evaporation of solvent-containing fullerenes.

https://iopscience.iop.org/article/10.1088/0953-4075/29/21/013/pdf

The absorption cross sections of and in the visible - UV region

The absolute vapour pressures over pure C60, C70, fullerite and over the binary C60/C70 system are calculated from ion intensities vs. temperature up to 800 K using the Knudsen effusion mass spectrometric method. The vapour pressures (Pa) of C60 and C70 are given as a function of temperature (K) by the equations: 



Corresponding Second Law enthalpy and entropy changes for sublimation are: 



Results are discussed in terms of sample purity and pretreatment and correlated with data obtained by other authors. Fullerenes containing residual organic solvents (fullerite) partly decompose upon thermal treatment to amorphous carbon.

Mass spectrometric investigations of fullerenes. I. Vapour pressure over the C60/C70 binary system

High temperature mass spectrometry has been used to study the vaporization properties of HoI3. Mass spectra of vapours indicate that HoI3 evaporates as HoI3(g) and Ho2I6(g) at temperatures around 1000 K. Ion current versus temperature data yield thermochemical values for positive ions and neutral molecules. The second law enthalpies ΔHsub °, 298K(HoI3) = 282 ± 12 kJ mol−1, ΔHsub, °298K(Ho2I6) = 352 ± 16 kJ mol−1, ΔHat°(HoI3) = 962 kJ mol−1, Δat°(Ho2I6) = 1962 kJ mol−1, ΔHf °298K(HoI3(g)) = −267 ± 18 kJ mol−1, ΔHf, °298K(Ho2I6(g)) = −738 ± 18 kJ mol−1 and ΔHr, °298K (2HoI3(g) → Ho2I6(g)) = −203 ± 12 kJ mol−1 are calculated from the experimental data. Estimated molecular parameters are used for the calculations of the thermodynamic functions by the third law method.

Mass spectra, vapour pressures and thermodynamic properties of HoI3

Mass spectrometric studies of tungsten bromides and oxybromides

Knudsen cell mass spectrometric measurements are reported on the composition of vapour over solid and fused NaI, CsI, HoI3, DyI3, (NaI + HoI3), (NaI + DyI3, (CsI + HoI3) and (CsI + DyI3 systems. For the determination of evaporation thermodynamics, the assignment of the essential ions to their neutral precursors was carried out by determining ionization efficiency curves. Due to the spread in electron energy, the linear extrapolation and vanishing current methods, which are generally used in high temperature mass spectrometry for evaluation of efficiency curves, could be used with limitations only. The analytical energy-distribution difference method was used to determine the fine structure of the ionization efficiency curves. The method uncovered relationships between the detected ions and neutral vapour-phase species, and served to determine thermodynamic data with improved precision.

A. Popovic

Papers

Mass spectrometric investigations of fullerenes. I. Vapour pressure over the C60/C70 binary system

Mass spectra, vapour pressures and thermodynamic properties of HoI3

Mass spectrometric studies of tungsten bromides and oxybromides

Determination of appearance energy for ions formed in the gaseous phase over alkali iodide and rare earth iodide systems

Mass spectrometric investigation of reaction between tungsten and bromine at high temperature