Density anomalies

The vapor density of acetic acid suggests a molecular weight much higher than the formula weight, 60.06. Indeed, the acid normally exists as a dimer (4), both in the vapor phase (5) and in solution (6). This vapor density anomaly has important consequences in engineering computations, particularly in distillations. 

The presence of a lithosphere with a thickness up to 100 km above the plume head obscures observations that could be made in terms of heat flow, gravity field or seismic structure. Establishing the temperature and flow fields beneath a hotspot thus becomes a difficult exercise. Several key parameters (Fig. 2) are poorly constrained and mostly result from theoretical fluid dynamics model, which underlines their large uncertainty. The temperature anomaly within the hotspot region is generally estimated to be approximately 200 100°C with large uncertainties (Shilling 1991 Sleep 1990). These temperature anomalies will induce smaller densities in the plume and the flux of the density anomalies is called buoyancy flux as defined in (Sleep 1990) ... 

Mahoney, M. W. Jorgensen, W. L., Quantum, intramolecular flexibility, and polarizability effects on the reproduction of the density anomaly of liquid water by simple potential functions, 7. Chem. Phys. 2001,115, 10758-10768... 

The O H stretching spectra of ethanol trimers and larger clusters cannot be conformationally resolved in a slit jet expansion [65, 77, 157], VUV-IR spectra [184] are even broader, sometimes by an order of magnitude, and band maxima deviate systematically by up to +50 cm 1 from the direct absorption spectra. We note that ethanol dimers and clusters have also been postulated in dilute aqueous solution and discussed in the context of the density anomaly of water ethanol mixtures [227], Recently, we have succeeded in assigning Raman OH stretching band transitions in ethanol-water, ethanol water, and ethanol water2 near 3550, 3410, and 3430cm, respectively [228],... 

Mahoney MW, Jorgensen WL (2000) A five-site model for liquid water and the reproduction of the density anomaly by rigid, nonpolarizable potential functions, J Chem Phys, 112 8910-8922... 

Model for Liquid Water and the Reproduction of the Density Anomaly by Rigid, Non-polarizable Potential Functions. 

Mahoney MW, Jorgensen WL. A five-site model for liquid water and the reproduction of the density anomaly by rigid, nonpolar-izable potential functions. J. Chem. Phys. 2000 112 8910-8922. Rick SW. A reoptimization of the five-site water potential TIP5P for use with Ewald sums. J. Chem. Phys. 2004 120 6085-6093. Horn HW, Swope WC, Pitera JW, Madura JD, Dick TJ, Hura GL, Head-Gordon T. Development of an improved four-site water model for bio-molecular simulations UP4P-Ew. J. Chem. Phys. 2004 120 9665-9678. 

Figure 12 Density anomalies relative to peridotite mantle versus depth in the lower mantle (blue) for candidate hulk compositions for the basaltic layer (red) and the underlying harzburgite layer (green). Note that the basaltic layer is denser but grows less so with increasing depth.

Formula (7.20) should be treated as the integrated sensitivity of the gravity data to the local density anomaly located at the depth z in the lower half-plane (z < 0). We can see that the sensitivity is inversely proportional to the square root of the depth of the density anomaly. 

One of the main problems with most of these analyses is that depth is a poor choice for comparison of data from different times and locations. Density is a more appropriate frame of reference for demonstrating whether or not changes have occurred (17). The parameter cr, is used to describe the density anomaly of seawater relative to freshwater at temperature t where cr, = p, -p(X) and where p(X) = 1000 kg m"3. The parameter p, (kilograms per cubic meter) is the true density of seawater at a salinity S and temperature t. A density of 1015.0 kg/m3 has a cr( = 15.0 kg m-3. 

Table II. Density Anomaly (ct,) Values of Characteristic Features in the Water-Column Profiles...

In studies of wood ehemistry it is important to remove extraetives with a multipurpose solvent sueh as methanol before wood density determination so that the correct extractive-free density data are gathered. Wood density anomalies led to extractive studies on larch species in the 1960s (Uprichard, 1963), with both polyphenols and arabinogalactan making large contributions to the apparent (unextracted) basic wood density. 

For the simplicity of calculations, we have discussed salinity in units of g/kg. This Absolute Salinity differs from the commonly measured Practical Salinity (scale PSS-78) by about 0.5% (Millero andLeung, 1976 Feistel, 2003 Jackett etal., 2006 Millero et al., 2008). For the estimates in this section, this difference is quantitatively irrelevant. The density anomaly of the Baltic Sea is even less than this, up to about 0.01 %, and is ignored here as well (Millero and Kremling, 1976). 

The density anomaly of the Baltic Sea is chiefly caused by a significant excess of calcium bicarbonate discharged from the rivers. The resulting density deviation of brackish water in the Baltic Sea can be estimated by the empirical relation between absolute salinity 5a, determined from density measurements, and practical salinity 5, determined from conductivity (Millero and Kremhng, 1976),... 

Franzese G., Malescio G., Skibinsky A., Buldyrev S., Stanley H. (2002) Metastable liquid-liquid phase transition in a single-component system with only one crystal phase and no density anomaly, Phys. Rev. A, 66(5), 051206-051220. 

Roberts C., Debenedetti P. (1996) Polyamorphism and density anomalies in network-forming fluids Zeroth- and first-order approximations, o/ Chem. Phys. 105(2), 658. 

Franzese, G. (2007) Differences between discontinuous and continuous soft-core attractive potentials The appearance of density anomaly, J. Mol. Liq., 136, 267-273... 

Table 2 predicts that, of the biphase processes, the aqueous version will attain particular importance because of the many advantages of water as the support. As a solvent, water has numerous anomalies (e.g., density anomaly, the only non-toxic and liquid hydride of the non-metals, pressure-dependence of the melting point, dielectric constant), and its two- or even three-dimensional structure is still not well understood (cf. Sections 2.1 -2.3). Some of the known properties are listed below ... 

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