Spectrometric, mass, Knudsen cell

Coppens et al. (4) used a combination of mass spectrometric and Knudsen cell techniques to determine the partial pressures necessary to define the equilibrium in the system V0(g) + Ge(g) = GeO(g) + V(g). The authors analyzed eight data points (1927-2145 K) by the 3rd law method and reported A H°(0 K) = 7.60 0.38 kcal mol" which actually applies to the reverse reaction (14). 

GOL/JEU] Goldfmger, P., Jeunehomme, M Mass spectrometric and Knudsen-Cell vaporization studies of group 2B-6B compounds, Trans. Faraday Soc., 59, (1963), 2851 -2867. Cited on pages 117, 118,279. 

Do of 1.40 eV for AI2 is within the error bounds of the experimental value of 1.55 0.15 eV determined by Stearns and Kohl (46) using a Knudsen cell mass spectrometric method and assuming a ground state. 

Knudsen Cell Mass-Spectrometric Heats of Formation... 

Most recently, a mass spectrometric study of the thermal decomposition of C2F4 in a graphite Knudsen cell was performed by Zmbov et al.180 The equilibrium between C2F4 and CF2 was examined between 1127 and 1244°K, and D CF2=CF2 was found to be 76.3 + 3 kcal/mole when corrected to 298°K the value for A/7298 CF2 becomes —39.0 kcal/mole. 

The Knudsen cell mass spectrometric method is well established and has been described in many reviews, as can be seen in references (6-10). It is an important method for equilibrium vapor studies of high temperature systems for temperatures up to approximately 3000 K. There is no other method presently available that permits the measurement of bond energies of minor molecular vapor components at such high tein)eratures. 

The gas species over solutions of hydrogen in liquid lithium were detected by mass spectrometric analysis of the saturated vapor effusing from a Knudsen cell. From the measurements of the gaseous equilibria... 

For Ba(0H)2(g) (4), the corrected dissociation energy of Ryabova and Gurvich (4), D 208.8 kcal mol", is in better agreement with the "adopted" value of 209.6 kcal mol , based on good Knudsen-cell mass-spectrometric measurements, than are the... 

Porter and Schoonmaker ( ) analyzed the vapor effusing from a Knudsen cell at 1121 K mass spectrometrically and derived the partial pressures of NaF(g) and NagF Cg) at that temperature. Using these reported partial pressures we calculate, by the 3rd law method, the value Aj,H (298.15 K) = 64.1 kcal mol for reaction (A). 

Drowart et al. (2,) used a modified Knudsen cell and a mass spectrometric technique to study the equilibrium FeS(g) + Mn(g) =... 

This is a thorough study of the evaporation of a-MnSe in the temperature range 1225 to 1780 K using the mass-spectrometric Knudsen-cell method. The predominant vaporisation process is... 

UY/DRO] Uy, O. M., Drowart, J., Determination by the mass spectrometric Knudsen cell method of the atomization energies of the gaseous aluminium chalcogenides, AI2, AlCu, AlCuS and AICUS2, Trans. Faraday Soc., 67, (1971), 1293-1301. Cited on pages 228, 229, 230, 532. 

SMO/DRO] Smoes, S., Drowart, J., Determination of the dissociation energy of selenium monoxide by the mass-spectrometric Knudsen-cell method, J. Chem. Soc. Faraday Trans., 80, (1984), 1171-1180. Cited on pages 118, 119, 562, 563, 564. 

Ion intensities and Knudsen cell temperatures are the quantities measured in the course of an investigation by the Knudsen effusion mass spectrometric method. Partial pressures are computed from these quantities for the vapor species identified. 

High-temperature Knudsen cell mass spectrometric measurements on the vapours above Al-Si alloys indicated the presence pf AI2, AlSi, and AlSia- Their atomization energies are 40 3.6, 59 3, and 150 5 kcal moF respectively. ... 

Maddrell s salt, which are interpreted as showing that kinetic effects are responsible for difficulties in converting the cyclic trimer into the linear polymeric forms. The potassium polyphosphate samples (Kurrol s salt) obtained from the fusion of potassium sulphate and phosphoric acid have chains terminated by OSOJ groups, according to i.r. spectra. Kinetic studies show a first-order dependence of polyphosphate concentration in the hydrolysis of Graham s salt to give trimetaphosphate and short-chain species. The vaporization of sodium metaphosphate from a Knudsen cell leads to predominantly monomeric, with some dimeric, species, according to mass-spectrometric data. ... 

The authors studied the thermal dissociation of thorium iodide mass-spectrometrically, and suggested that substantial decomposition to lower iodides and iodine vapour occurs when both the solid and liquid are heated. Coarse ciystals of Thl4(cr), prepared from the elements, were used to minimise the oxygen and water contents of the samples used in the (unspecified) Knudsen cell. The variation of the intensities of the TI1I4, TI1I3, TI1I2,12 and I ions observed in the mass-spectrometer was studied from ca. 625 to 800 K. 

The potassium hydrate K OH2 was detected by Chupka " in a mass spectrometric study of ions emerging from a heated Knudsen cell containing KCl salt, and water as an impurity. The ion clusters Ar OH2, where M = Li, Na, and K, were also mass spectrometrically observed in a study of ions in flames by Hayhurst and Sugden. " The ions were produced by spraying an aqueous solution of the alkali chlorides in a premixed H2, 02,N2 flame at 1 atm. The authors also attempted to measure the ionic equilibria -h H2O = M OH2. However, their data are inconsistent, which is not surprising, considering the complexity of the experimental conditions and arrangement. 

Mass spectrometric analysis of a molecular beam selected from the effusate distribution coming from a Knudsen cell provides information about the identity of... 

A similar situation exists for alloys where a component pressure is not measurable under the temperatures for measurable vapor pressures of other components. Examples are Hf in Ni-Al-Hf [85]), Cr in Mn-Cr [104], and rare earth (RE) in Mg-RE alloys [105]. The latter study was based on a Knudsen cell without the use of a mass spectrometer. Nonetheless the approach is applicable to a mass spectrometric study. Depending on the alloy system, several approaches can be taken. In some cases the effect of controlled additions of the low-pressure component on a fixed ratio of the measured elements is the only required information [100,102]. Albers et al. [85] and Zaitsev et al. [104] did a Gibbs-Duhem integration to obtain the activities of the low vapor pressure component. Pahlman and Smith [105] assumed Raoultian behavior in the terminal RE-Mg solution and moved across the phase diagram to derive the activity of the RE component in each two-phase region. 

We have studied the interactions of HNO3, HCl and HBr with liquid sulfuric acid surfaces using both time dependent uptake and equilibrium vapor pressure methods in a Knudsen cell reactor equipped with mass spectrometric detection. Measured solubilities will be presented as Henry s law coefficients along with thermochemical parameters. 

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