Milton Farber

Mass spectrometric determination of the thermodynamic properties of the vapour species from alumina

The vapour species over Al2O3(c) were determined mass spectrometrically from an alumina effusion cell. These data are in good agreement with previously published weight loss data since the partial pressures of the suboxides, AlO, Al2O, AlO2 and Al2O2 were found to be of the same order as those of the elements, Al and O. New values were determined for the ΔHf298K of AlO, Al2O, AlO2 and Al2O2 of 17.0 ± 2.0, –33.2 ± 3.0, –44.3 ± 2.0 and –113.6 ± 2.0 kcal/mol, respectively. Excellent agreement was obtained between second and third law studies.

Mass spectrometric determination of the heats of formation of the silicon fluorides SiF(g), SiF2(g) and SiF3(g)

An effusion-mass spectrometric study of the reaction of SiF4(g) with Si(c, 1) in the temperature range 1590–1782 K has been completed. Second and third law reaction enthalpies were obtained for SiF4(g)+ Si(g)= 2SiF2(g), SiF4(g)+ SiF2(g)= 2SiF3(g), and SiF2(g)+ Si(g)= 2SiF(g). From the heats of reaction third law ΔHf298 values of –5.8 ± 0.5, –140.6 ± 0.3 and –259.3 ± 0.5 kcal mol–1 were obtained for SiF(g), SiF2(g) and SiF3(g), respectively. For the dissociation of SiF(g)→(3P0)Si(g)+(2P)F(g) a third law dissociation energy value of 131.2 ± 0.5 kcal mol–1 was calculated.

Experimental determination of heats of formation of negative ions and electron affinities of several boron and aluminium fluorides

Thermodynamic properties for the negative ions of boron and aluminium fluorides were obtained by means of the effusion-mass spectrometric method over the temperature range 1100 to 1900 K. Studies were conducted involving negative ions with neutral molecules for the isomolecular reactions BF–2(g)+ F(g)→BF2(g)+ F–(g), BF3(g)+ BF–2(g)→BF(g)+ BF–4(g), AlF2(g)+ F–(g)→AlF–2(g)+ F(g) and 2AlF2(g)+ AlF–2(g)→2AlF(g)+ AlF–4(g). The heats of formation, ΔHf298, for the ions BF–2(g), AlF–2(g), AlF–4(g), and BF–4(g) obtained from the reaction thermodynamics were – 191.7 ± 3, – 232.1 ± 3, – 500 ± 3 and – 433 kcal mol–1, respectively. The electron affinities for BF2 and AlF2 were 50.7 ± 3 and 53.1 ± 3 kcal mol–1, respectively.

Effusion-mass spectrometric study of thermodynamic properties of vanadium and vanadium nitride

Effusion-mass spectrometric studies were performed on the vapour species in equilibrium above VN(c) in the temperature range 1900 to 2412 K. From an analysis of the reactions involved, ΔHf298 values of 122.4 ± 5 kcal/mol (second law) and 120.4 ± 2 kcal/mol (third law) were obtained for VN(g), yielding a dissociation energy, D°298, for gaseous VN of 114.1 kcal/mol. An appearance potential of 8 ± 1 eV was recorded for VN(g). The thermodynamic analysis of the vapour species over the solid state yielded a second law ΔHf of –52 ± 1.5 kcal/mol for VN(c). Studies made in this temperature range resulted in a third law heat of fusion of 4.30 ± 0.45 kcal/mol for vanadium. The second and third law mass spectrometric ΔHf298 values of 122.8 ± 1.5 and 123.0 ± 0.2 kcal/mol, respectively, for V(g) were in good agreement with Knudsen third law weight loss experiments at 2092 and 2122 K, which yielded ΔHf298 values of 123.3 and 122.9 kcal/mol.

Mass spectrometric determination of the heats of formation of the silicon subchlorides SiCl(g), SiCl2(g) and SiCl3(g)

An effusion-mass spectrometric determination of the reaction of SiCl4(g) with Si(c, l) in the temperature range 1593–1792 K has been completed. Second and third law reaction enthalpies were obtained for SiCl4(g)+ Si(g)= 2SiCl2(g), SiCl4(g)+ SiCl2(g)= 2SiCl3(g), and SiCl2(g)+ Si(g)= 2SiCl(g). From the heats of reaction third law ΔHf298 values of 47.1 ± 0.6, –40.6 ± 0.6 and –93.3 ± 0.5 kcal mol–1 were obtained for SiCl(g), SiCl2(g) and SiCl3(g), respectively. For the dissociation of SiCl(g)→(3P0)Si(g)+(2P3/2)Cl(g) a third law dissociation energy value of 88.6 ± 0.6 kcal mol–1 was calculated.

Dissociation energies of BeF and BeCl and the heat of formation of BeClF

An effusion-mass spectrometric investigation of the Be–Cl–F system to obtain bond energies of BeF and BeCl and the heat of formation of the mixed halide BeClF has been completed. A study of the ion intensities of the species produced in the simultaneous reaction of chlorine gas and BeF2 vapour with elemental beryllium was made in the temperature range 1415 to 1592 K. The reaction enthalpies calculated from these species yield second and third law ΔHf298 values of –139.0 ± 4 and –140.5 ± 2 kcal mol–1, respectively, for BeClF(g). The dissociation energies of 104 kcal mol–1 obtained for BeCl and 144 kcal mol–1 for BeF agree with those previously reported from spectroscopic, molecular flow effusion, and transport investigations.

Effusion mass spectrometric determination of thermodynamic properties of the gaseous mono– and di-hydroxides of calcium and KCaO(g)

Effusion mass spectrometric measurements were made to obtain thermodynamic data for the gaseous mono- and di-hydroxides of calcium. An investigation of the reaction CaO(c)+½H2(g)= CaOH(g) in the temperature range 1720–1983 K led to third and second law ΔH°298 values of 444.3 ± 4 kJ mol–1 and 443.1 ± 16 kJ mol–1, respectively. The corresponding ΔH°f298 values for CaOH(g) were –190.8 ± 8 kJ mol–1 and –192.0 ± 16 kJ mol–1. The third law D0 for Ca–OH was 404.2 ± 8 kJ mol–1. Two reactions were employed for obtaining thermal data for Ca(OH)2(g) CaO(c)+H2O(g)= Ca(OH)2(g) in the temperature range 1800–1950 K, and the isomolecular reaction 2CaOH(g)= Ca(g)+Ca(OH)2(g) in the temperature range 1720–1900 K. Third- and second-law values for the ΔH°f298 of Ca(OH)2(g) obtained from these reactions were –605.8 ± 8 kJ mol–1 and –602.5 ± 20 kJ mol–1, respectively. The third-law D0 for Ca+2OH was 854.8 ± 8 kJ mol–1. A knowledge of the K reactions with the mineral matter ingredients in the combustion products of coal is necessary for obtaining definitive electrical conductivities for design of coal-fired electric power plants. Thermodynamic data were obtained for KCaO(g) species from the reaction CaOH(g)+K(g)= KCaO(g)+½H2(g) in the temperature range 1880–1950 K. A third-law heat of reaction of –215.1 ± 16 kJ mol–1 led to a third-law ΔH°f298 of –328.0 ± 20 kJ mol–1 for KCaO(g).

Electron-impact and thermodynamic studies of potassium metaborate

An effusion–mass spectrometric investigation of the thermodynamic properties of KBO2(g) has been made in the temperature range 1053–1240 K. The KBO2(g) molecule fragments to over 90% of its initial concentration at electron ionization energies 2 eV above its ionization potential of 8 ± 1 eV. The fragmentation processes were studied to ionization energies as high as 70 eV, with the appearance of K+, BO+2 and BO+ fragments. Data obtained for the sublimation process, KBO2(c)→ KBO2(g), and for the vaporization process, KBO2(1)→ KBO2(g), yielded second- and third-law reaction heats. A third-law ΔH⊖f298 of –672.4 ± 10 kJ mol–1 and a second-law ΔH⊖f298 of –672.8 ± 10 kJ mol–1 were obtained for KBO2(g). A heat of melting, ΔH⊖m, at the melting point of 1220 K was found to be 31.8 ± 4 kJ mol–1.

Effusion-mass spectrometric study of the thermodynamic properties of AlO– and AlO–2

Thermodynamic properties were obtained for negative ions of the lower aluminium oxides by means of the effusion-mass spectrometric method over the temperature range 2080 to 2222 K. Second and third law studies were conducted involving negative ions with neutral molecules for the isomolecular reactions AlO(g)+ Cl–(g)= AlO–(g)+ Cl(g), AlO2(g)+ Cl–(g)= AlO–2(g)+ Cl(g). The heats of formation, ΔHf298, for the ions AlO–(g) and AlO–2(g) obtained from the reaction thermodynamics were –64.6 ± 3 and – 139.3 ± 3 kcal/mol, respectively. The electron affinities were (AlO)= 84.8 ± 3 and (AlO2)= 94.7 ± 3 kcal/mol.