Vapor Composition over Solid Indium Trichloride and in ­Indium Chloride Unsaturated Vapor

The dependence of indium trichloride saturated and unsaturated vapor pressure on temperature was studied in the range of 630–950 K by static methods using a quartz membrane zero‐manometer and taking into account the volume of its working chamber and substance mass. The thermodynamic data on the process of dissociation of dimeric molecules and sublimation of monomer and dimer from solid indium trichloride were calculated: ΔH⁰_subl InCl₃(g)₂₉₈ = 155.3 ± 6.2 kJ · mol^–1; ΔS⁰_subl InCl₃(g)₂₉₈ = 199.5 ± 7.9 J · mol^–1 · K^–1; ΔH⁰_subl In₂Cl₆(g)₂₉₈ = 159.3 ± 6.2 kJ · mol^–1; ΔS⁰_subl In₂Cl₆(g)₂₉₈ = 207.1±3.8 J · mol^–1 · K^–1; ΔH⁰_dis In₂Cl₆(g)₂₉₈ = 152.6 ± 5.5 kJ · mol^–1 and ΔS⁰_dis In₂Cl₆(g)₂₉₈ = 171.6 ± 5.2 J · mol^–1 · K^–1. The saturated vapor over solid indium trichloride consists mainly of a mixture of monomeric and dimeric molecules (InCl₃ and In₂Cl₆), and the content of the latter is slightly growing with increasing temperature.     

Thermodynamics of vaporization of gallium trichloride

The unsaturated and saturated pressures of gallium trichloride vapor were measured by the static method with membrane-gauge manometers in wide pressure (0.2–760 Torr) and temperature (313–1071 K) intervals. Scanning calorimetry was used to determine the thermodynamic characteristics of GaCl₃ fusion. The thermodynamic characteristics were obtained for sublimation, fusion, vaporization, and association in the vapor of GaCl₃ molecules. The enthalpies of formation and the absolute entropies of GaCl₃ in the liquid and gaseous phases and Ga₂Cl₆ in the gaseous phase were calculated using literature data. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1266–1269, July, 2007.     

Nachweis und thermochemische Charakterisierung des Gasphasenmoleküls VOCl2

Proof of Existence and Thermochemical Characterization of the Gaseous Molecule VOCl₂ By use of the Knudsen-cell mass spectrometry the existence of VOCl₂(g). is proven. Lines of fragmentation are set up for VOCl₃(g). The vapor above V₂O₃(s) with Cl₂(g) is examined. The sublimation of VOCl₂ is measured at a temperature of 550–620 K. By 2nd law calculations the heat of sublimation is defined. The calculation for the gaseous VOCl₂ leads to Δ_BH°(VCl₂(g), 298 K) = ?(130,4 ± 1,5) kcal · mol^?1. The influence of VOCl₂(g) for chemical vapor transport reactions of vanadium oxides with Cl₂ is discussed by equilibrium calculations.     

Zur Bedeutung von V2O3(OH)4(g) für den chemischen Transport von V2O5(s) in Anwesenheit von Wasser. Nachweis des Gasteilchens,thermodynamische Daten und Modellrechnungen

V₂O₃(OH)₄(g), Proof of Existence, Thermochemical Characterization, and Chemical Vapor Transport Calculations for V₂O₅(s) in the Presence of Water By use of the Knudsen-cell mass spectrometry the existence of V₂O₃(OH)₄(g) is shown. For the molecules V₂O₃(OH)₄(g), V₄O₁₀(g), and V₄O₈(g) thermodynamic properties were calculated by known Literatur data. The influence of V₂O₃(OH)₄(g) for chemical vapor transport reactions of V₂O₅(s) with water ist discussed. Δ_BH°(V₂O₃(OH)₄(g), 298) = –1920 kJ · mol^–1 and S°(V₂O₃(OH)₄(g), 298) = 557 J · K^–1 · mol^–1, Δ_BH°(V₄O₁₀(g), 298) = –2865,6 kJ · mol^–1 and S°(V₄O₁₀(g), 298) = 323.7 J · K^–1 · mol^–1, Δ_BH°(V₄O₈(g), 298) = –2465 kJ · mol^–1 and S°(V₄O₈(g), 298) = 360 J · K^–1 · mol^–1.     

Calculation of Some Thermodynamic Properties and Detonation Parameters of 1‐Ethyl‐3‐Methyl‐H‐Imidazolium Perchlorate, [Emim][ClO4], on the Basis of CBS‐4M and CHEETAH Computations Supplemented by VBT Estimates

This paper estimates some thermochemical (in kcal mol^–1) and detonation parameters for the ionic liquid, [emim][ClO₄] and its associated solid in view of its investigation as an energetic material. The thermochemical values estimated, employing CBS‐4M computational methodology and volume‐based thermodynamics (VBT) include: lattice energy, U_POT([emim][ClO₄]) ≈? 123 ± 16 kcal · mol^–1; enthalpy of formation of the gaseous cation, Δ_fH°([emim]⁺, g) = 144.2 kcal · mol^–1 and anion, Δ_fH°([ClO₄]^–, g) = –66.1 kcal · mol^–1; the enthalpy of formation of the solid salt, Δ_fH°([emim][ClO₄],s) ≈? –55 ± 16 kcal · mol^–1 and for the associated ionic liquid, Δ_fH^o([emim][ClO₄],l) = –52 ± 16 kcal · mol^–1 as well as the corresponding Gibbs energy terms: Δ_fG°([emim][ClO₄],s) ≈? +29 ± 16 kcal · mol^–1 and Δ_fG^o([emim][ClO₄],l) = +24 ± 16 kcal · mol^–1 and the associated standard absolute entropies, of the solid [emim][ClO₄], S°₂₉₈([emim][ClO₄],s) = 83 ± 4 cal · K^–1 · mol^–1. The following combustion and detonation parameters are assigned to [emim][ClO₄] in its (ionic) liquid form: specific impulse (I_sp) = 228 s (monopropellant), detonation velocity (V_oD) = 5466 m · s^–1, detonation pressure (p_C–J) = 99 kbar, explosion temperature (T_ex) = 2842 K.     

Equilibrium sublimation and thermodynamic properties of SnSe and SnSe2

Knudsen effusion studies of the sublimation of polycrystalline SnSe and SnSe₂, prepared by annealing and chemical vapor transport reactions, respectively, have been carried out using vacuum microbalance techniques in the temperature ranges 736–967 K and 608–760 K, respectively. From experimental mass-loss data for the sublimation reaction SnSe(s) = SnSe(g), the recommended values for the heat of formation and absolute entropy of SnSe(s) were calculated to be ΔH°_298,f = ?86.4 ± 9.9 kJ · mol^?1 and S°₂₉₈ = 89.0 ± 7.1 J · K^?1 · mol^?1. From mass-loss data for the decomposition reaction \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm SnSe}_{\rm 2} ({\rm s)} = {\rm SnSe(s)} + \frac{1}{{\rm x}}{\rm Se}_{\rm x} ({\rm g) (x} = 2 - 8) $\end{document}, the recommended values for the heat of formation and absolute entropy of SnSe₂(s) were determined to be ΔH°_298,f = ?118.1 ± 15.1 kJ · mol^?1 and S°₂₉₈ = 111.8 ± 11.8 J · K^?1 mol^?1.     

Formation and Stability of Gaseous WS2Cl2, WS2Br2 and WS2I2 – A Combined Experimental and Theoretical Study

Gaseous WS₂Cl₂ and WS₂Br₂ are formed by the reaction of solid WS₂ with chlorine resp. bromine at temperatures of about 1000 K. This could be shown by mass spectrometric measurements. The heats of formation and entropies of WS₂Cl₂ and WS₂Br₂ have been determined by means of mass spectrometry (MS) and quantum chemical calculations (QC). WS₂I₂ could not be detected by experimental methods. This is in line with the quantum chemically determined equilibrium constant of the formation reaction. The following values are given:, Δ_fH⁰₂₉₈(WS₂Cl₂) = –230.8 kJ · mol^–1 (MS), Δ_fH⁰₂₉₈(WS₂Cl₂) = –235.0 kJ · mol^–1 (QC),, S⁰₂₉₈(WS₂Cl₂) = 370.7 J · K^–1 · mol^–1 (QC) and, c_p⁰_T(WS₂Cl₂) = 103.78 + 7.07 × 10^–3 T – 0.93 × 10⁵ T^–2 – 3.25 × 10^–6 T² (298.15 K < T < 1000 K) (QC). Δ_fH⁰₂₉₈(WS₂Br₂) = –141.9 kJ · mol^–1 (MS), Δ_fH⁰₂₉₈(WS₂Br₂) = –131.5 kJ · mol^–1 (QC),, S⁰₂₉₈(WS₂Br₂) = 393.9 J · K^–1 · mol^–1 (QC) and, c_p⁰_T(WS₂Br₂) = 104.84 + 5.32 × 10^–3 T – 0.75 × 10⁵ T^–2 – 2.45 × 10^–6 T² (298.15 K < T < 1000 K) (QC). Δ_fH⁰₂₉₈(WS₂I₂) = –18.0 kJ · mol^–1 (QC), S⁰₂₉₈(WS₂I₂) = 409.9 J · K^–1 · mol^–1 (QC) and, c_p⁰_T(WS₂I₂) = 105.17 + 4.77 × 10^–3 T – 0.67 × 10⁵ T^–2 – 2.19 × 10^–6 T² (298.15 K < T < 1000 K) (QC). These molecules have the expected C_2v‐symmetry.     

Polymorphism of paracetamol

The thermodynamic relationship between crystal modifications of paracetamol was studied by alternative methods. Temperature dependence of saturated vapor pressure for polymorphic modifications of the drug paracetamol (acetaminophen) was mea sured and thermodynamic functions of the sublimation process calculated. Solution calorimetry was carried out for the two modifications in the same solvent. Thermodynamic parameters for sublimation for form I (monoclinic) were found: ΔG _sub²⁹⁸=60.0 kJ mol⁻¹; ΔH _sub²⁹⁸=117.9±0.7 kJ mol⁻¹; ΔS _sub²⁹⁸=190±2 J mol⁻¹ K⁻¹. For the orthorhombic modification (form II), the saturated vapor pressure could only be studied at 391 K. Phase transition enthalpy at 298 K, ΔH _tr²⁹⁸(I→II)=2.0±0.4 kJ mol⁻¹, was derived as the difference between the solution enthalpies of the noted polymorphs in the same solution (methanol). Based on ΔH _tr²⁹⁸ (I→II), differences between temperature dependencies of heat capacities of both modifications and the vapor pressure value of form II at 391 K, the temperature dependence of saturated vapor pressure and thermodynamic sublimation parameters for modification II were also estimated (ΔG _sub²⁹⁸=56.1 kJ mol⁻¹; ΔH _sub²⁹⁸=115.9±0.9 kJ mol⁻¹; ΔS _sub²⁹⁸=200±3 J mol⁻¹ K⁻¹). The results indicate that the modifications are monotropically related, which is in contrast to findings recently reported found by classical thermochemical methods.     

Synthese und Kristallstrukturen der Phosphaniminato-Komplexe [AlCl2(NPEt3)]2, [GaI2(NPEt3)]2 und [GaI2(NPPh3)]2

Synthesis and Crystal Structures of the Phosphoraneiminato Complexes [AlCl₂(NPEt₃)]₂, [GaI₂(NPEt₃)]₂, and [GaI₂(NPPh₃)]₂ [AlCl₂(NPEt₃)]₂ ( 1 ) is made according to the known method by reaction of aluminium trichloride with the silylated phosphaneimine Me₃SiNPEt₃ in acetonitrile; it is isolated as colourless, moisture sensitive crystals. The phosphoraneiminato complexes [GaI₂(NPEt₃)]₂ ( 2 ) and [GaI₂(NPPh₃)]₂ ( 3 ), on the other hand, are obtained by redox reactions as pale yellow crystals; ( 2 ) of “gallium(I) iodide” with Me₃SiNPEt₃ in toluene and ( 3 ) of gallium with N-iodine triphenylphosphaneimine, INPPh₃, in tetrahydrofuran. 1 and 3 are characterized spectroscopically and by crystal structure determinations; 2 is characterized only crystallographically. 1 : Space group Pbca, Z = 4; lattice dimensions at –70 °C: a = 1232.6(2), b = 1341.1(2), c = 1393.4(3) pm, R₁ = 0.0315. 1 forms centrosymmetric molecules in which the Al atoms are linked via Al–N bonds of the two (NPEt₃^–) groups; with 185.0 and 184.4 pm these bonds are of almost the same lengths. 2 : Space group Pbca, Z = 4; lattice dimensions at –80 °C: a = 1380.0(1), b = 1311.0(1), c = 1429.1(1) pm, R₁ = 0.0273. 2 crystallizes isotypically with 1 . The gallium atoms of the centrosymmetric Ga₂N₂ four-membered ring are connected with Ga–N distances of equal length (190.9 pm). 3 · THF: Space group P2₁2₁2₁, Z = 2; lattice dimensions at –140 °C: a = 1494.6(1), b = 1536.3(1), c = 974.6(1) pm, R₁ = 0.0382. 3 forms dimeric molecules in which the gallium atoms are linked via the N atoms of the (NPPh₃^–) groups to form a non-planar Ga₂N₂ four-membered ring of C₂ symmetry with Ga–N bonds of equal lengths – within standard deviations – of 194.7 pm. The phosphoraneiminato groups are arranged in a synperiplanar way.     

The cationic polymerization of fluoral—III. Thermodynamics of polymerization in solution

The equilibrium between fluoral in dichloromethane solution and live condensed liquid polyfluoral has been investigated between 22 and 43°C. Equilibrium monomer concentrations gave: ΔH_ac°(298 K) = -50-8 ± 2·3 kJ mol^?1 and ΔS_sc° (298 K) = -142·7 ± 7·4 J K^-1 mol^-1. With the aid of calibration and monomer vaporization data, thermodynamic values for the polymerization of liquid monomer to liquid polymer were also calculated: ΔH_tc° (298 K) = -47 ± 3 kJ mol^-1 and ΔS_1e° (298 K) = -97 ± 10 J K^-1 mol^-1.     

Eine neue Methode zur Messung von temperaturabhängigen Partialdrücken in geschlossenen Systemen. Die Bestimmung der Bildungsenthalpie und -entropie von PtI2(s)

Determination of Temperature Dependent Partial Pressures in Closed Systems – a New Method. The Heat of Formation for PtI₂(s) A new method to determine temperature dependent partial pressures of gaseous species in equilibria with condensed phases in closed systems (silica ampoules) at temperatures up to 1000 °C and pressures p_i 0.01 < p_i < 10 bar is presented. It is based on the determination of the change of mass in the gasphase caused by solid-gas transition at higher temperatures of substances which are deposited at one end of the ampoule. The results of the measurements give informations about reaction mechanisms, enthalpies and entropies. The reliability of the method is demonstrated at the example of the system Pt/I₂. The heat of formation and the entropy of PtI₂(s) (δ_BH°(PtI₂(s), 298) = –51.4 kJ · mol^–1, S°(PtI₂(s), 298) = 119.3 J · K^–1 · mol^–1) are computed from experimental results. The heat of thermal decomposition of PtI₂(s) was reconsidered by Knudsen Mass Spectrometry.     

A laser flash photolysis kinetic study of reactions of the Cl2− radical anion with oxygenated hydrocarbons in aqueous solution

A laser photolysis–long path laser absorption (LP‐LPLA) experiment has been used to determine the rate constants for H‐atom abstraction reactions of the dichloride radical anion (Cl₂⁻) in aqueous solution. From direct measurements of the decay of Cl₂⁻ in the presence of different reactants at pH = 4 and I = 0.1 M the following rate constants at T = 298 K were derived: methanol, (5.1 ± 0.3)·10⁴ M⁻¹ s⁻¹; ethanol, (1.2 ± 0.2)·10⁵ M⁻¹ s⁻¹; 1‐propanol, (1.01 ± 0.07)·10⁵ M⁻¹ s⁻¹; 2‐propanol, (1.9 ± 0.3)·10⁵ M⁻¹ s⁻¹; tert.‐butanol, (2.6 ± 0.5)·10⁴ M⁻¹ s⁻¹; formaldehyde, (3.6 ± 0.5)·10⁴ M⁻¹ s⁻¹; diethylether, (4.0 ± 0.2)·10⁵ M⁻¹ s⁻¹; methyl‐tert.‐butylether, (7 ± 1)·10⁴ M⁻¹ s⁻¹; tetrahydrofuran, (4.8 ± 0.6)·10⁵ M⁻¹ s⁻¹; acetone, (1.41 ± 0.09)·10³ M⁻¹ s⁻¹. For the reactions of Cl₂⁻ with formic acid and acetic acid rate constants of (8.0 ± 1.4)·10⁴ M⁻¹ s⁻¹ (pH = 0, I = 1.1 M and T = 298 K) and (1.5 ± 0.8) · 10³ M⁻¹ s⁻¹ (pH = 0.42, I = 0.48 M and T = 298 K), respectively, were derived. A correlation between the rate constants at T = 298 K for all oxygenated hydrocarbons and the bond dissociation energy (BDE) of the weakest C‐H‐bond of log k_2nd = (32.9 ± 8.9) − (0.073 ± 0.022)·BDE/kJ mol⁻¹ is derived. From temperature‐dependent measurements the following Arrhenius expressions were derived: k (Cl₂⁻ + HCOOH) = (2.00 ± 0.05)·10¹⁰·exp(−(4500 ± 200) K/T) M⁻¹ s⁻¹, E_a = (37 ± 2) kJ mol⁻¹ k (Cl₂⁻ + CH₃COOH) = (2.7 ± 0.5)·10¹⁰·exp(−(4900 ± 1300) K/T) M⁻¹ s⁻¹, E_a = (41 ± 11) kJ mol⁻¹ k (Cl₂⁻ + CH₃OH) = (5.1 ± 0.9)·10¹²·exp(−(5500 ± 1500) K/T) M⁻¹ s⁻¹, E_a = (46 ± 13) kJ mol⁻¹ k (Cl₂⁻ + CH₂(OH)₂) = (7.9 ± 0.7)·10¹⁰·exp(−(4400 ± 700) K/T) M⁻¹ s⁻¹, E_a = (36 ± 5) kJ mol⁻¹ Finally, in measurements at different ionic strengths (I) a decrease of the rate constant with increasing I has been observed in the reactions of Cl₂⁻ with methanol and hydrated formaldehyde. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 169–181, 1999     

Kinetics of Oxidation Processes in the System Co/Ga studied by in situ X‐Ray Diffraction

Oxidation processes in the system Co/Ga were studied by in situ X‐ray diffraction at temperatures between 800 and 1000 °C. Experiments were performed with metal powders and planar substrates. Oxidation of cobalt‐rich alloys, Co_1‐xGa_x, results in the formation of mixtures of cobalt‐ and gallium‐containing oxides. During oxidation of the intermetallic compounds CoGa and CoGa₃ only gallium is oxidized, and dense tarnishing layers of β‐Ga₂O₃ are formed. In all cases the oxide products are only intermediate products on the way to thermodynamic equilibrium, i.e. total oxidation of both metals. The kinetics during oxidation of the intermetallic compound CoGa was studied in detail by time resolved in situ X‐ray diffraction. After an induction time the kinetics can be described by a parabolic rate law with an activation energy of 312 kJ mol^—1. From the decrease of the parabolic rate constant with decreasing oxygen partial pressure and the observation of pore formation at the metal‐oxide interface it can be concluded that (i) outward diffusion of Ga‐ions through β‐Ga₂O₃ is the rate determining step during this solid state reaction, and (ii) Ga‐ions are mobile by means of gallium vacancies.     

Synthesis and Properties of [Ba(CHZ)(BT)(H2O)2]n as a New Energetic Coordination Compound

In order to enhance the thermal stability of the barium salt of 5,5′‐bistetrazole (H₂BT), carbohydrazide (CHZ) was used to build [Ba(CHZ)(BT)(H₂O)₂]_n as a new energetic coordination compound by using a simple aqueous solution method. It was characterized by FT‐IR spectroscopy, elemental analysis, and single‐crystal X‐ray diffraction. The crystal belongs to the monoclinic P2₁/c space group [a = 8.6827(18) Å, b = 17.945(4) Å, c = 7.2525 Å, β = 94.395(2)°, V = 1126.7(4) ų, and ρ = 2.356 g · cm^–3]. The Ba^II cation is ten‐coordinated with one BT^2–, two shared carbohydrazides, and four shared water molecules. The thermal stabilities were investigated by differential scanning calorimetry (DSC) and thermal gravity analysis (TGA). The dehyration temperature (T_dehydro) is at 187 °C, whereas the decomposition temperature (T_d) is 432 °C. Non‐isothermal reaction kinetics parameters were calculated by Kissinger's method and Ozawa's method to work out E_K = 155.2 kJ · mol^–1, lgA_K = 9.25, and E_O = 158.8 kJ · mol^–1. The values of thermodynamic parameters, the peak temperature (while β → 0) (T_p0 = 674.85 K), the critical temperature of thermal explosion (T_b = 700.5 K), the free energy of activation (ΔG^≠ = 194.6 kJ · mol^–1), the entropy of activation (ΔS^≠ = –66.7 J · mol^–1), and the enthalpy of activation (ΔH^≠ = 149.6 kJ · mol^–1) were obtained. Additionally, the enthalpy of formation was calculated with density functional theory (DFT), obtaining Δ_fH°₂₉₈ ≈ 1962.6 kJ · mol^–1. Finally, the sensitivities toward impact and friction were assessed according to relevant methods. The result indicates the compound as an insensitive energetic material.     

Donorstabilisierte Galliumdihalogenide Ga2X4·2D (X = Cl,Br; D = Donormolekül): Ein experimenteller Beitrag zu den Variationsmöglichkeiten der Ga‐Ga‐Einfachbindung

Donor‐stabilized Galliumdihalides Ga₂X₄·2D (X = Cl, Br; D = Donor): An Experimental Contribution on the Variation of the Gallium‐Gallium Single Bond During the disproportionation of metastable GaX‐solutions (X= Cl, Br) donor‐stabilized galliumdihalides are formed as oxidized products. According to X‐ray structure analyses they all exhibit dimeric entities DX₂Ga‐GAX₂D (D= THF, NHEt2, NEt3, 4‐^tButylpyridin or Br^‐), which means these compounds are isoelectronic with ethane and could schematically be regarded as representatives of catenulate or alkane‐like gallium subhalides: Ga_n(X, D)_2n+2. The gallium‐gallium bond in these compounds is shorter than in the organometallic compounds such as R₂Ga‐GaR₂. The comparison of the bonding situation in the galliumdihalides, particularly of the gallium‐gallium bond, shows clearly the influence by donor molecules as well as by halogen ligands.     

[Ga(en)3][Ga3Se7(en)] · H2O: Ein Galliumchalkogenid mit Ketten aus [Ga3Se6Se2/2(en)]3–-Bicyclen

[Ga(en)₃][Ga₃Se₇(en)] · H₂O: A Gallium Chalcogenide with Chains of [Ga₃Se₆Se_2/2(en)]^3– Bicycles The new selenidogallate [Ga(en)₃][Ga₃Se₇(en)] · H₂O ( I ) was produced from a ethylendiamine suspension of Ga and Se at 130 °C. I crystallizes in the orthorhombic space group Pna2₁ with unit constants a = 1347.9(3) pm, b = 961.6(1) pm, c = 1967.6(4) pm and Z = 4. The crystal structure contains an anion so far not observed in gallium chalcogenides. It is built from [Ga₃Se₆Se_2/2(en)]^3– bicycles of three Ga^IIIL₄ tetrahedra (L = en, Se) connected via selenium corners to linear chains. The cations, Ga^III ions coordinated by three ethylendiamine in a distorted octahedral geometry are positioned in the holes of the hexagonal rod packing of these chains.     

Mass Spectrometric Investigations of Thermodynamic Properties of the RbCl/GdCl3 System

The vaporization of pure RbCl, GdCl₃, and RbCl‐GdCl₃ samples of different phase compositions was investigated in the temperature range between 666 K and 982 K by use of the Knudsen effusion mass spectrometry. The gaseous species RbCl, Rb₂Cl₂, GdCl₃, and RbGdCl₄ were identified in the equilibrium vapours and their partial pressures were determined. The enthalpy of dissociation of RbGdCl₄(g), Δ_dissH°(859 K) = 263.1 ± 7.7 kJ mol^—1, was evaluated by second law treatment of the equilibrium partial pressures. The thermodynamic activities of RbCl and GdCl₃ were obtained at 800 K in the two‐phase fields {Rb₃GdCl₆(s) + liquid} and {RbGd₂Cl₇(s) + GdCl₃(s)}. The Gibbs free energies of formation of the pseudo‐binary phases Rb₃GdCl₆(s), Δ_fG°(800 K) = —75.1 ± 2.5 kJ mol^—1 and RbGd₂Cl₇(s), Δ_fG°(800 K) = —40.6 ± 1.2 kJ mol^—1, were evaluated from the thermodynamic activities of the components. The results are compared with the available literature data.     

The recombination of iodine atoms in the presence of nitric oxide

The recombination of iodine atoms following the flash photolysis of iodine in the presence of nitric oxide is interpreted through the mechanism with k₁ = 3.5 × 10⁹ l.²/mol²·sec; k₂ ≈ 1 × 10¹¹ l./mol·sec; k₃ = 2.1 × 10⁷ l./mol·sec at 298°K; E₃ = 11 kJ/ mol; and ΔH°₁ = 76 ± 6 kJ/mol. Lower and upper limits for the equilibrium constant are also established. The absorption spectrum of INO has been extended down to 223 nm and extinction coefficients for the region of 223–310 nm and 360–460 nm have been measured.     

Infrared Spectroscopic Studies on the Surface Chemistry of High‐Surface‐Area Gallia Polymorphs

Polymorphs α, β, and γ of Ga₂O₃ having hexagonal (corundum‐type), monoclinic and cubic (spinel‐type) structure, respectively, were prepared in a high‐surface‐area form, and characterized by powder X‐ray diffraction. Nitrogen adsorption at 77 K showed these gallia samples to have specific surface areas of 77 (α‐Ga₂O₃), 40 (β‐Ga₂O₃) and 120 m² g^?1 (γ‐Ga₂O₃). Fourier transform infrared spectroscopy of adsorbed carbon monoxide (at 77 K) and pyridine (at room temperature) showed that the three gallia polymorphs have a very similar surface Lewis acidity, regardless of their different crystal structures. This Lewis acidity was assigned, mainly, to coordinatively unsaturated tetrahedral Ga³⁺ ions situated on the surface of the small crystallites which constitute the different metal oxide varieties. Ga³⁺···CO adducts formed after CO adsorption gave (in all cases) a characteristic C–O stretching band at 2195–2200 cm^?1, while Lewis‐type adducts formed with adsorbed pyridine were characterized by IR absorption bands at 1610–1612 and 1446–1450 cm^?1. The three (partially hydroxylated) gallia polymorphs showed also a very weak Brønsted acidity, which they manifested by forming hydrogen‐bonded adducts with both CO and pyridine; however no protonation of adsorbed pyridine occurred.     

The distinction of gallium(I) tetrachloroaluminate,Ga[AlCl4], from gallium dichloride

Ga[AlCl₄] is obtained as single crystals via the reduction of gallium trichloride with aluminum and slow cooling of the melt. It crystallizes in the monoclinic system, space group p2₁/n, with a = 716.4(1), b = 1017.9(2), c = 926.7(1) pm, β = 93.21(1)°. Unlike in gallium dichloride, Ga[GaCl₄]], where Ga⁺ has a dodecahedral, eight-coordinate surrounding, a 6 + 2 + 1 coordination is adopted in Ga[AlCl₄] that is similarly observed not only in Ga₂[Ga₂Br₆] and in tin (II) and lead (II) chalcogenides but also in (the almost isotypic) K[AlCl₄].