Spectrometric, mass, Knudsen cell method

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). 

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. 

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. 

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. 

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). 

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. 

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. 

We have developed several new measurement techniques ideally suited to such conditions. The first of these techniques is a High Pressure Sampling Mass Spectrometric method for the spatial and temporal analysis of flames containing inorganic additives (6, 7). The second method, known as Transpiration Mass Spectrometry (TMS) (8), allows for the analysis of bulk heterogeneous systems over a wide range of temperature, pressure and controlled gas composition. In addition, the now classical technique of Knudsen Effusion Mass Spectrometry (KMS) has been modified to allow external control of ambient gases in the reaction cell (9). Supplementary to these methods are the application, in our laboratory, of classical and novel optical spectroscopic methods for in situ measurement of temperature, flow and certain simple species concentration profiles (7). In combination, these measurement tools allow for a detailed fundamental examination of the vaporization and transport mechanisms of coal mineral components in a coal conversion or combustion environment. 

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