Partial pressure measurements

The number of ions i produced from a gas in the ion source is proportional to the emission current i, to the specific ionization Sggj, to a geometry factor f representing the ionization path inside the ionization source, to the relative ionization probability RlPgaj. and to the partial pressure Pggj. This number of ions produced is, by definition, made equal to the sensitivity Egas times the partial pressure Pg  

Almost all gases form fragments during ionization. To achieve quantitative evaluation one must either add the ion flows at the appropriate peaks or measure (with a knovm fragment factor [FF]) one peak and calculate the overall ion flow on that basis  

The partial pressure is calculated from the ion flow measured for a certain fragment by multiplication w/ith two factors. The first factor w/ill depend only on the nitrogen sensitivity of the detector and thus is a constant for the device. The second w/ill depend only on the specific ion properties. 

These factors will have to be entered separately for units w/ith direct partial pressure indication (at least for less common types of ions). 

In order to maintain the number of ions arriving at the ion trap, it is necessary to multiply the number above with the transmission factor TF(m), which will be dependent on mass, in order to take into account the permeability of the separation system for atomic number m (analogous to this, there is the detection factor for the SEMP it, however, is often already contained in TF). The transmission factor (also ion-optical transmission) is thus the quotient of the ions measured and the ions produced. 

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Free-energy-concentration diagrams have been used in the study of the thermodynamic influence on the non-stoichiometry of the solid titanium carbide deposited from H2-CH4-TiCl4 gas mixtures at 1 900 K. The authors show how, from the partial pressure measurements of Ti vapour over a range of... 

Partial pressure measurement in vacuum technology , Balzers A. G. (ed.) Liechtenstein. 

NH3 H2S mean deviation to partial pressures measured by Ginzburg et al. frei/Per cent KHH BR EMNP... 

NH3 partial pressure measurements made in the same manner used for the NH3-Hp0 measurements. 

These measurements were reduced to NH3 partial pressure measurements using Equation 2 given above. In this case, the reference solution is the composition reached at zero salt concentration at the bottom of Table 23. The ammonia partial pressure above this solution can be inferred from Table 1 where PNH3/wt % NH3 at 0.1 wt % NH3 has a value of 1.23. This information gives the following values for P J. and mVref-... 

Partial pressure measurement devices which are In common use comprise the measurement system proper (the sensor) and the control device required for Its operation. The sensor contains the Ion source, the separation system and the Ion trap. The separation of Ions differing In masses and charges Is often effected by utilizing phenomena which cause the Ions to resonate In electrical and magnetic fields. 

A partial pressure measurement unit is characterized essentially by the following properties (DIN 28 410) ... 

The linearity range is that pressure range for the reference gas (Nj, Ar) in which sensitivity remains constant within limits which are to be specified ( 10 % for partial pressure measurement devices). 

When the sputter-ion pumps are installed one should ensure that the magnetic fields will not interfere with the operation of other devices (ionization vacuum gauges, partial pressure measurement units, etc.). Mounting devices for the sputter-ion pumps may not short circuit the inductance flow and thus weaken the air gap inductance and pumping speed. 

Doizi, D., et al. (2007), Total and Partial Pressure Measurements for the Sulphur-iodine Thermochemical Cycle , Int. J. Hydrogen Energy, 32 (9), 1183-1191. 

To measure the gas phase speciation, the choice of optical spectrometries was made. These online techniques allow concentration measurements (Hartmann, 2009) and then partial pressures measurements without altering the gas phase composition. 

The identification and quantification (partial pressure measurement) of the gaseous components in vacuum systems is of increasing importance in vacuum technology. This is achieved by the widely applied method of residual gas analysis. The simple theory of this is stated and relevant examples illustrate the application. 

Chapter 5 considers the methods available for the measurement of both total and partial pressure in vacuum systems. For total pressure, the methods of measurement are described and, importantly, the uncertainty associated with that measurement is discussed. This may influence the choice of gauge. Also in Chapter 5, residual gas analysers (RGAs) for vacuum partial pressure measurements are described. These devices are being used increasingly for diagnostic work on vacuum systems. 

Fig. 5.7. Stability analysis of a process control loop for the reactive magnetron sputtering of high-index metal oxides. The control of discharge power to stabilize the oxygen partial pressure set point is modeled within the framework of the Berg model. A cycle time of 100 ms and process uncertainties for discharge current and oxygen partial pressure measurements are assumed, (from [71])...

The anesthetics are introduced from conventional vaporizers. For the determination of MAC, an initial concentration is used that permits movement of the rats in response to noxious stimulation. A tail clamp is applied for 1 minor until the animal moves, and the anesthetic partial pressure is measured by gas chromatography. If the animal moves, the partial pressure is increased by 0.2% or 0.3% atmospheres. After equilibration for 30 min, the tail clamp is applied again and the anesthetic partial pressure measured by gas chromatography. This procedure is repeated until the partial pressures bracketing movement-nonmovement are determined for each rat. 

The numerical value of kt in (2-3) depends on how activity is defined and on the units in which concentration is expressed (molarity, mole fraction, partial pressure). Measurement of the absolute activity, or chemical potential, of an Individual ion is one of the classical unsolved problems. Since we cannot measure absolute ion activity, we are then necessarily interested in the next best—comparative changes in activities with changing conditions. To obtain comparative values numerically, we measure activity with respect to an arbitrarily chosen standard state under a given set of conditions of temperature and pressure, where the substance is assigned unit activity. The value of ki in (2-3) thus depends on the arbitrary standard state chosen accordingly, the value of the equilibrium constant also depends on the choice of standard states. 

T cal k" mol" from partial pressure measurements over the W-W0 (cr) system. 

T cal K mol from partial pressure measurements over. The adopted value, AjH (WgOg, g, 298.15 K)... 

The adopted value, A H (Wg0g, g, 298.15 K) = -483.6 kcal mol", was reduced from A H (Wg0g, g, 1450 K) = -474.1 kcal mol" of Ackermann and Rauh ( ), who studied the sublimation behavior of the tungsten-oxygen system over the temperature range from 1300 to 16000 K by mass spectrometry, mass effusion and x-ray diffraction, and determined A G (W20g, g) = -474,100 + 110.26T cal K" mol" from partial pressure measurements over V-VO (cr). They reviewed the previous determinations (, 2, 3, 4) of the thermodynamic... 

Gases enter the equilibrium expression as partial pressures, measured in atmospheres. 

In addition to the estimated properties, we measured the thermochemistry of several important vapor species. These measurements were conducted in a Knudsen effusion cell using special line-of-sight vaporization under subambient pressures with flowing O2 and H2O vapor mixtures [4]. The gaseous species over silica [5], manganese oxide [6], lanthana, alumina, and palladium metal were detected and relative partial pressures measured as a function of temperature. These vapor pressure measurements were calibrated by using the known metal atom or binary metal oxide volatility as a calibration source. Oxide species concentrations were measured relative to that of a reference compound, e.g., metal atom. The identification of oxide and hydroxide compounds was facilitated by Ae technique of threshold electron ionization [7]. These data were then evaluated using estimated entropy functions and the third law temperatures. 

Denis Doizi et al., Hydrogen Production by the Iodine-Sulphur Thermochemical Cycles Partial Pressure Measurements , Transactions of American Nuclear Society 2005 Annual Meeting, Volume 92, San Diego, California, June 5-9, 2005. 

Sridhar, K.R. and Blanchard, J.A. (1999) Electronic conduction in low oxygen partial pressure measurements using an amperometric zirconia oxygen sensor. Sens. Actuators B, 59, 60-7. 

Gomez et al. [145] describe skimmer diaphragms to define the molecular beam originating in the Knudsen cell for the analysis thereby increasing the potential for Oj and partial pressure measurements in the cell. 

Glyceric acid was oxidised on a Pt(4.3%)-Bi(3.9%)/C at pH 2, 4, 5 and 6. The initial reaction rates were determined as the initial slope of the conversion. Oxygen partial pressure measurements of the reaction medium showed an immediate rapid increase in dissolved oxygen, thus indicating that reactions took place in the kinetic regime (see Figure 2). 

For formic acid an aqueous phase dimerisation constant of 0.00775 kg mol (32), and a gas phase value of 345.0 atm" (32) were used together with three partial pressure measurements (29) to estimate a K h of 5.2x10 mol kg l atm l t 25°C, Table II. While the data are scattered, this estimate is in good agreement with the thermodynamically calculated value. 

The strongest interactions in an electrolyte solution occur between ions of opposite sign. Within the Pitzer model these are accounted for by the B a and Cca functions, which are known for most solutes. The mixing parameters By and /yk, while having relatively small effect in dilute solutions such as seawater, are important in the much more concentrated mixtures typical of the atmospheric aerosol. Further examples of the effects of individual ions on partial pressures can be seen in partial pressure measurements, e.g. (6.50L... 

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