Helium density Table

DENSITY MEASUREMENTS. Helium densities of the extracts were determined so that the gravimetric sorption data could be converted to volume fractions needed to calculate x parameters. The results of these measurements are shown in Table III. The density of the extract was observed to decrease with increasing size of the added alkyl group. These results are qualitatively similar to those of Liotta t al.(14), who studied the effects of O-alkylation on the physical structure of the native Illinois No. 6 coal. 

TABLE III. Helium Densities, CO2 Surface Areas, and Solubilities of Illinois No. 6 Extracts... 

Equation 16 can be readily solved for a hypothetical helium lattice with density equal to the liquid density. Table II summarizes the results of... 

During the course of laser resonance experiments it was noticed that the central wavelengths shift depending on the helium density. Thus, the resonance line shapes at various target gas conditions were measured precisely with a reduced laser bandwidth and an improved wavelength calibration [18]. Figure 5 shows resonance profiles taken for the 597.26 nm line at different pressures ranging from 530 mb to 8.0 bar at temperatures of 5.8-6.3 K. The results are summarized in Table 2. 

In this density, volume is defined as the sum of the volume of the solid material and any closed pores within the solid. These pores cannot be penetrated by any fluid and become part of the powder volume. A mass of catalyst is placed in a flask of known volume, and the amount of helium needed to fill the flask measured, giving the powder volume by difference. Care should be taken to dehydrate all pores thoroughly. Because helium is used as the displacing fluid, this density is sometimes called the helium density. See Table 7.1 for an example of typical values. 

In addition, the critical temperature Tc, the critical pressure pc, the critical density Qc, the triple-point temperature Ttr, and the triple-point pressure ptr are given for some elements. For the element helium, the table also contains data for the A, point, at which liquid helium passes from the normal-fluid phase helium I (above the A point) to the superfluid phase helium II (below the A point), for " He and He. 

The SSTAR reactor is coupled to a supercritical carbon dioxide (S-CO2) Brayton cycle power converter. It provides higher cycle efficiency than a helium ideal gas Brayton cycle or a Rankine saturated steam cycle operating at the same core outlet temperature. A key contributor to the high efficiency is the low amount of work (PdV work) to compress S-CO2 immediately above its critical temperature - due to the high S-CO2 density. Table XXII-6 compares the densities of S-CO2 at cycle conditions versus those for helium in the Eskom Pebble Bed Modular Reactor (PBMR) as well as typical liquid coolants the S-CO2 density is more like that of an ordinary liquid. Thus, the S-CO2 temperature and pressure at the low end of the cycle are designed close to but slightly greater than the critical temperature (30.98°C) and pressure (7.373 MPa) to exploit the small PdV work of compression. 

The temperature of the treatment is more important than its duration. The carbon obtained after the BP treatment has a much more fractured surface (Fig. 2d) and a significantly reduced surface area. The fraction of micropores falls below 80%. The heavy damage to the pore structure is also reflected in the low-pressure hysteresis, observed only in this carbon. The lower helium density of the sample M3SEN reported in Table 2 is an additional sign of a severely weakened skeleton. 

Small-angle x-ray diffraction was used to determine the lattice parameter uo of the 2D hexagonal pore system of the sample. A geometrical pore radius [2] R estimated from the relation = (V3/27t) ao[PmVp/(H- pmVp)] (with the matrix density pm = 2.16 g cm from helium density measurements) is also given in Table 1. 

Table 13.1). In the solid P(CH4) > P(CD4) but the curves cross below the melting point and the vapor pressure IE for the liquids is inverse (Pd > Ph). For water and methane Tc > Tc, but for water Pc > Pc and for methane Pc < Pc- As always, the primes designate the lighter isotopomer. At LV coexistence pliq(D20) < Pliq(H20) at all temperatures (remember the p s are molar, not mass, densities). For methane pliq(CD4) < pLiq(CH4) only at high temperature. At lower temperatures Pliq(CH4) < pliq(CD4). The critical density of H20 is greater than D20, but for methane pc(CH4) < pc(CD4). Isotope effects are large in the hydrogen and helium systems and pLIQ/ < pLiQ and P > P across the liquid range. Pc < Pc and pc < pc for both pairs. Vapor pressure and molar volume IE s are discussed in the context of the statistical theory of isotope effects in condensed phases in Chapters 5 and 12, respectively. The CS treatment in this chapter offers an alternative description.

An ideal gas is a relatively low-density gas. The pressure p, temperature T, and specific volume v of an ideal gas are related by an equation of state, pv = RT, where i is a constant for a particular gas and is called the gas constant. Air, helium, and carbon dioxide are ideal gases. The properties of an ideal gas can be found in tables such as air tables. 

Clouds of gas in the interstellar medium are called gaseous nebulas. These nebulas are regions of the interstellar medium with above-average density. The proportions of elements in the interstellar medium conform to the abundances in the table, that is, 90% hydrogen atoms, 9% helium atoms and less than 1% heavier atoms, where these percentages now refer to relative numbers of atoms rather than relative mass. 

On surfaces of some d band metals, the 4= states dominated the surface Fermi-level LDOS. Therefore, the corrugation of charge density near the Fermi level is much higher than that of free-electron metals. This fact has been verified by helium-beam diffraction experiments and theoretical calculations (Drakova, Doyen, and Trentini, 1985). If the tip state is also a d state, the corrugation amplitude can be two orders of magnitude greater than the predictions of the 4-wave tip theory, Eq. (1.27) (Tersoff and Hamann, 1985). The maximum enhancement factor, when both the surface and the tip have d- states, can be calculated from the last row of Table 6.2. For Pt(lll), the lattice constant is 2.79 A, and b = 2.60 A . The value of the work function is c() w 4 cV, and k 1.02 A . From Eq. (6.54), y 3.31 A . The enhancement factor is... 

A plot of density versus pore radius, from the data in Table 21.2, is shown in Fig. 21.3. The horizontal line indicates the true density obtained by helium pycnometry. This higher density by gas displacement reflects the volume of pores smaller than about 18 A. 

Estimated compositions ofthe giant planets are given in Table 14.3, normalized to the solar composition. The relative proportions of rock and volatiles are estimated from mean densities, the rock compositions are assumed to be chondritic, and the ratios of hydrogen to helium are derived from spectroscopic or spacecraft measurements of atmosphere compositions. 

Table 3.1 lists measured spectral moments of rare gas mixtures at various temperatures. (We note that absorption in helium-neon mixtures has been measured recently [253]. This mixture absorbs very weakly so that pressures of 1500 bar had to be used. Under these conditions, one would expect significant many-body interactions the measurement almost certainly does not represent binary spectra.) For easy reference below, we note that the precision of the data quoted in the Table is not at all uniform. Accurate values of the moments require good absorption measurements over the whole translational frequency band, from zero to the highest frequencies where radiation is absorbed. Such data are, however, difficult to obtain. Good measurements of the absorption coefficient a(v) require ratios of transmitted to incident intensities, /(v)//o, that are significantly smaller than unity and, at the same time, of the order of unity, i.e., not too small. Since in the far infrared the lengths of absorption paths are limited to a few meters and gas densities are limited to obtain purely... 

H2 He He rotovibrational band. The density dependence of the H2-He enhancement spectrum in the fundamental band of hydrogen has been measured previously, using a trace of hydrogen in helium of thousands of amagats [121, 175, 142] ternary moments were measured at room temperature. The measurements suggest again greater values of the spectral moments, Table 6.7. 

Table III provides some of the experimentally determined measurements obtained by using IREB collective ion accelerators. All of the listed experiments, except the last, used accelerated protons. The last entry is for helium ions. A similar series of experiments is needed using HDCC accelerators. In addition, it may be of considerable interest to use hydrogen, deuterium, helium, and nitrogen gases for the positive-ion sources. The ability of the HDCC to ionize and transport positive ions at high local densities and at relatively low costs promises to make this new technology an effective research tool.

Supercritical Fluid. To be useful as a mobile phase in chromatography, a supercritical fluid must have a relatively low critical temperature and pressure, and a relatively high density/solvating power at experimentally accessible pressures and temperatures. The former criterion excludes water and most common organic solvents, whereas the latter excludes such low-boiling substances as helium, hydrogen, and methane. Commonly used fluids are listed in Table I. 

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