Density measurement gases

Considerable effort will be made to predict the onset of overpressures ahead of the drill bit. The most reliable indioations are gas readings, porosity - depth trends, rate of penetration and shale density measurements. 

Arsenic pentafluoride (arsenic(V) fluoride), AsF, is a colorless gas that condenses to a yellow Hquid its dielectric constant is 12.8 at 20 °C. It is formed by reaction of a mixture of bromine and antimony pentafluoride with arsenic trifluoride. The molecule is a trigonal bipyramid and is somewhat dissociated as indicated by vapor density measurements. 

Measurements in large fluidized beds of fine particles indicate that bubble coalescence often ceases within a short distance above the gas distributor plate. Indications from density measurements or single bubble velocities are that bubble velocity Ug and diameter often reach maximum stable values, which are invariant with height or fluidizing gas velocity. 

Many methods have been used to determine the deuterium eontent of hydrogen gas or water. For H2/D2 mixtures mass speetroseopy and thermal eonduetivity ean be used together with gas ehromatography (alumina aetivated with manganese ehloride at 77 K). For heavy water the deuterium eontent ean be determined by density measurements, refraetive index ehange, or infrared speetroseopy. 

Suppose such a vapor-density measurement shows that a given volume of ethanol at 100°C and one atmosphere weighs 1.5 times as much as the same volume of oxygen gas at 100°C and one atmosphere. Since equal volumes contain equal numbers of molecules at the same temperature and pressure (Avogadro s Hypothesis), one molecule of the unknown gas must weigh 1.5 times the weight of a molecule of 02. Therefore,... 

We see that, for a given pressure and temperature, the greater the molar mass of the gas, the greater its density. Equation 10 also shows that, at constant temperature, the density of a gas increases with pressure. When a gas is compressed, its density increases because the same number of molecules are confined in a smaller volume. Similarly, heating a gas that is free to expand at constant pressure increases the volume occupied by the gas and therefore reduces its density. The effect of temperature on density is the principle behind hot-air balloons the hot air inside the envelope of the balloon has a lower density than that of the surrounding cool air. Equation 10 is also the basis for using density measurements to determine the molar mass of a gas or vapor. 

Here m is electron mass, N is the number density of gas molecules, B is the rotational constant, and q = (8/15)jta02Q2, ag and Q being respectively the Bohr radius and the quadrupole moment of the molecule. The experimental energy loss rate for nitrogen agreed well with Eq. (8.1) over the ambient temperature range 300-735 K. Typical values are -0.5 ts at 300 K and 6 torr, and -1 p.s at 735 K and 4 torr. The variation of relaxation time with gas temperature and pressure are also well predicted. For oxygen, Mentzoni and Rao (1965) measure relaxation times -160-350 ns for T = 300-900 K and at 3 torr. 

The three most common ways of obtaining true density measurements are gas pycnometry (gas displacement), liquid displacement, and flotation in a liquid. These three techniques have been compared based on accuracy, ease of use, and instrumentation [63], and the results are summarized in Table 4. Gas pycnometry will be discussed in this section because of its wide use and ease of operation. 

Optical data storage, high throughput experimentation, 7 414t Optical density measurements, 19 221 Optical detectors, gas chromatography,... 

Thus, there are two limitations of the pycnometric technique mentioned possible adsorption of guest molecules and a molecular sieving effect. It is noteworthy that some PSs, e.g., with a core-shell structure, can include some void volume that can be inaccessible to the guest molecules. In this case, the measured excluded volume will be the sum of the true volume of the solid phase and the volume of inaccessible pores. One should not absolutely equalize the true density and the density measured by a pycnometric technique (the pycnometric density) because of the three factors mentioned earlier. Conventionally, presenting the results of measurements one should define the conditions of a pycnometric experiment (at least the type of guest and temperature). For example, the definition p shows that the density was measured at 298 K using helium as a probe gas. Unfortunately, use of He as a pycnometric fluid is not a panacea since adsorption of He cannot be absolutely excluded by some PSs (e.g., carbons) even at 293 K (see van der Plas in Ref. [2]). Nevertheless, in most practically important cases the values of the true and pycnometric densities are very close [2,7],... 

Research and development technologists at the Dow Chemical Company can characterize materials in a variety of ways. One material property that is especially critical in polymer foaming and processing technology is density. A tool used for measuring the density of a material is called a pycnometer. There are many different manual and automatic types to choose from. For extremely accurate and precise density measurements, an easy-to-use, fully automatic gas displacement pycnometer is utilized. Analyses are commenced with a single keystroke. Once an analysis is initiated, data are collected, calculations performed, and results displayed without further operator intervention. 

Vapor density measurements (37, 226) and mass spectroscopy (226, 300) were used to show that ClFgO is monomeric in the gas phase. The relatively high boiling point and Trouton constant of ClFgO imply its association in the liquid phase. More specific evidence about the nature of this association was obtained from the vibrational spectra... 

Differential pressure meters are widely used. Temperature, pressure, and density affect gas density and readings of differential pressure meters. For that reason, many commercial flowmeters that are based on measurement of differential pressure often have integral temperature and absolute pressure measurements in addition to differential pressure. They also frequently have automatic temperature and pressure compensation. 

We saw in connection with the discussion of Figure 9.5 that measurable gas adsorption occurs even at gas pressures as low as 10 10 torr. As a matter of fact, the two-dimensional density of the adsorbed molecules is not low enough to conform to the two-dimensional ideal gas law even when the pressure is on the order of 10 10 torr. A question of considerable practical importance, then, is how low the pressure must be for an initially clean surface to remain that way for a reasonable period of time. The above reference to adsorption cites equilibrium data that are not useful for answering questions of rate. 

It seems to me that we can scarcely progress in our understanding of the structural and kinetic effects of the H-bond without knowing the AG and AH terms involved, so I intend to discuss some methods of determining them. The references will provide simple examples of the methods mentioned. The most significant AG and AH values are those evaluated from equilibrium measurements in the gas phase—either by classical vapour density measurements, the second virial coefficient [1], or from, spectroscopic, specific heat or thermal conductance [2], or ultrasonic absorptions [3]. All these methods essentially measure departures from the ideal gas laws. The second virial coefficient provides a measure of the equilibrium constant for the formation of collision dimers in the vapour as was emphasized by Dr. Rowlinson in the discussion, this factor is particularly significant as only the monomer-dimer interaction contributes to it. 

Excited atoms can be conveniently produced by flashing CSe2 in a large excess of inert gas which prevents any significant temperature rise. Relaxation processes can be identified, and their rates measured, by kinetic spectroscopy and plate density measurement. The atoms are produced by direct photolysis into the 43P, states... 

Methods of measurement of coal density include use of a gas pycnometer and particle density by mercury porosimetry. However, the difference in density values using different gases must be recognized since, for example, density values measured by nitrogen may be greater than those obtained when helium is used. Density measurement depends on adsorption of gas molecules, and differences (between nitrogen and helium) may be due to nitrogen adsorption on the coal surface. 

The skeletal density, also called the true density, is defined as the density of a single particle excluding the pores. That is, it is the density of the skeleton of the particle if the particle is porous. For nonporous materials, skeletal and particle densities are equivalent. For porous particles, skeletal densities are higher than the particle density. Measurements of the skeletal density can be made by liquid or gas pycnometers. 

As previously discussed, the density of the fluid whose flow is to be measured can have a large effect on flow sensing instrumentation. The effect of density is most important when the flow sensing instrumentation is measuring gas flows, such as steam. Since the density of a gas is directly affected by temperature and pressure, any changes in either of these parameters will have a direct effect on the measured flow. Therefore, any changes in fluid temperature or pressure must be compensated for to achieve an accurate measurement of flow. 

Fig.2.7 shows the basic observables as derived from a Chandra observation of the regular cluster A478 (Sun et al. 2003). From the basic observations, the three dimensional gas temperature, gas density, and gas pressure distributions can be derived. In addition, as already mentioned, with sufficiently long observations, the heavy element abundance distributions can be measured by studies of the energy spectrum (e.g., see Fig.2.2). 

The first evidence for the existence of dark matter has been provided by dynamical measures performed on the Coma cluster, in 1930 by F. Zwicky. Since that time, our understanding of clusters has greatly increased. There is nearly 100 times more mass in clusters than in the stars that can be seen within them. However, there is much more baryons seen in X-ray clusters in form of hot gas than in stars. The discovery of this hot gas through its X-ray emission has revolutionized the study of clusters. Indeed X-ray observations allows to measure gas density and gas temperatures with a high accuracy and they are likely to provide the most accurate mass measurements. Clusters therefore provide a fascinating laboratory for cosmological studies their stellar, bary-... 

In multiphase flow metering, it is usually required to distinguish hydrocarbon from water. If the liquid phase is "oil continuous," the water fraction can be determined by dielectric constant measurement at microwave frequencies because the dielectric constant of dry hydrocarbon is on the order of 2 to 4 and that of water is 82. Naturally, density measurement can also distinguish water from oil. The next requirement is to distinguish the flow of liquid from the flow of gas in a system where the two will try to separate and travel at different velocities. Cross-correlation by nuclear techniques can measure the density of the stream twice (a short vertical distance apart) and correlate the fluctuations in density with time to determine velocity. Multiphase flow metering is a new and evolving technology,... 

Ammonia is readily detectable in air in the range of a few parts per million by its characteristic odor and alkaline reaction. Specific indicators, such as Nessler s reagent (Hgk in KOH), can detect ammonia in a concentration of 1 ppm. For the quantitative determination of ammonia in air, synthesis gas and aqueous solutions, these methods can be used74 Acidimetry and Volumetric Analysis By Absorption, Gas Chromatography, Infrared Absorption, Thermal Conductivity Measurement, Electrical Conductivity Measurement, Measurement of Heat of Neutralization, and Density Measurement (for aqueous ammonia). 

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